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Space weather

Space weather is a branch of space physics and aeronomy, or heliophysics, concerned with the varying conditions within the Solar System and its heliosphere. This includes the effects of the solar wind, especially on the Earth's magnetosphere, ionosphere, thermosphere, and exosphere. Though physically distinct, space weather is analogous to the terrestrial weather of Earth's atmosphere (troposphere and stratosphere). The term "space weather" was first used in the 1950s and popularized in the 1990s. Later, it prompted research into "space climate", the large-scale and long-term patterns of space weather.

History
For many centuries, the effects of space weather were noticed, but not understood. Displays of auroral light have long been observed at high latitudes.

Beginnings
In 1724, George Graham reported that the needle of a magnetic compass was regularly deflected from magnetic north over the course of each day. This effect was eventually attributed to overhead electric currents flowing in the ionosphere and magnetosphere by Balfour Stewart in 1882, and confirmed by Arthur Schuster in 1889 from analysis of magnetic observatory data.

In 1852, astronomer and British Major General Edward Sabine showed that the probability of the occurrence of geomagnetic storms on Earth was correlated with the number of sunspots, demonstrating a novel solar-terrestrial interaction. The solar storm of 1859 caused brilliant auroral displays and disrupted global telegraph operations. Richard Carrington correctly connected the storm with a solar flare that he had observed the day before near a large sunspot group, demonstrating that specific solar events could affect the Earth.

Kristian Birkeland explained the physics of aurorae by creating artificial ones in his laboratory, and predicted the solar wind.

The introduction of radio revealed that solar weather could cause extreme static or noise. Radar jamming during a large solar event in 1942 led to the discovery of solar radio bursts, radio waves over a broad frequency range created by a solar flare.

The 20th century
In the 20th century, the interest in space weather expanded as military and commercial systems came to depend on systems affected by space weather. Communications satellites are a vital part of global commerce. Weather satellite systems provide information about terrestrial weather. The signals from satellites of a global positioning system (GPS) are used in a wide variety of applications. Space weather phenomena can interfere with or damage these satellites or interfere with the radio signals with which they operate. Space weather phenomena can cause damaging surges in long-distance transmission lines and expose passengers and crew of aircraft travel to radiation, especially on polar routes.

The International Geophysical Year increased research into space weather. Ground-based data obtained during IGY demonstrated that the aurorae occurred in an auroral oval, a permanent region of luminescence 15 to 25° in latitude from the magnetic poles and 5 to 20° wide. In 1958, the Explorer I satellite discovered the Van Allen belts, regions of radiation particles trapped by the Earth's magnetic field. In January 1959, the Soviet satellite Luna 1 first directly observed the solar wind and measured its strength. A smaller International Heliophysical Year (IHY) occurred in 2007–2008.

In 1969, INJUN-5 (or Explorer 40 ) made the first direct observation of the electric field impressed on the Earth's high-latitude ionosphere by the solar wind. In the early 1970s, Triad data demonstrated that permanent electric currents flowed between the auroral oval and the magnetosphere.

The term "space weather" came into usage in the late 1950s as the space age began and satellites began to measure the space environment. The term regained popularity in the 1990s along with the belief that space's impact on human systems demanded a more coordinated research and application framework.

US National Space Weather Program
The purpose of the US National Space Weather Program is to focus research on the needs of the affected commercial and military communities, to connect the research and user communities, to create coordination between operational data centers, and to better define user community needs. NOAA operates the National Weather Service's Space Weather Prediction Center.

The concept was turned into an action plan in 2000, an implementation plan in 2002, an assessment in 2006 and a revised strategic plan in 2010. A revised action plan was scheduled to be released in 2011 followed by a revised implementation plan in 2012.

Phenomena
Within the Solar System, space weather is influenced by the solar wind and the interplanetary magnetic field carried by the solar wind plasma. A variety of physical phenomena is associated with space weather, including geomagnetic storms and substorms, energization of the Van Allen radiation belts, ionospheric disturbances and scintillation of satellite-to-ground radio signals and long-range radar signals, aurorae, and geomagnetically induced currents at Earth's surface. Coronal mass ejections are also important drivers of space weather, as they can compress the magnetosphere and trigger geomagnetic storms. Solar energetic particles (SEP) accelerated by coronal mass ejections or solar flares can trigger solar particle events, a critical driver of human impact space weather, as they can damage electronics onboard spacecraft (e.g. Galaxy 15 failure), and threaten the lives of astronauts, as well as increase radiation hazards to high-altitude, high-latitude aviation.

Spacecraft electronics

Some spacecraft failures can be directly attributed to space weather; many more are thought to have a space weather component. For example, 46 of the 70 failures reported in 2003 occurred during the October 2003 geomagnetic storm. The two most common adverse space weather effects on spacecraft are radiation damage and spacecraft charging.

Radiation (high-energy particles) passes through the skin of the spacecraft and into the electronic components. In most cases, the radiation causes an erroneous signal or changes one bit in memory of a spacecraft's electronics (single event upsets). In a few cases, the radiation destroys a section of the electronics (single-event latchup).

Spacecraft charging is the accumulation of an electrostatic charge on a nonconducting material on the spacecraft's surface by low-energy particles. If enough charge is built up, a discharge (spark) occurs. This can cause an erroneous signal to be detected and acted on by the spacecraft computer. A recent study indicated that spacecraft charging is the predominant space weather effect on spacecraft in geosynchronous orbit.

Spacecraft orbit changes
The orbits of spacecraft in low Earth orbit (LEO) decay to lower and lower altitudes due to the resistance from the friction between the spacecraft's surface (i.e. , drag) and the outer layer of the Earth's atmosphere (or the thermosphere and exosphere). Eventually, a LEO spacecraft falls out of orbit and towards the Earth's surface. Many spacecraft launched in the past few decades have the ability to fire a small rocket to manage their orbits. The rocket can increase altitude to extend lifetime, to direct the re-entry towards a particular (marine) site, or route the satellite to avoid collision with other spacecraft. Such maneuvers require precise information about the orbit. A geomagnetic storm can cause an orbit change over a few days that otherwise would occur over a year or more. The geomagnetic storm adds heat to the thermosphere, causing the thermosphere to expand and rise, increasing the drag on spacecraft. The 2009 satellite collision between the Iridium 33 and Cosmos 2251 demonstrated the importance of having precise knowledge of all objects in orbit. Iridium 33 had the capability to maneuver out of the path of Cosmos 2251 and could have evaded the crash, if a credible collision prediction had been available.

Humans in space
The exposure of a human body to ionizing radiation has the same harmful effects whether the source of the radiation is a medical X-ray machine, a nuclear power plant, or radiation in space. The degree of the harmful effect depends on the length of exposure and the radiation's energy density. The ever-present radiation belts extend down to the altitude of crewed spacecraft such as the International Space Station (ISS) and the Space Shuttle, but the amount of exposure is within the acceptable lifetime exposure limit under normal conditions. During a major space weather event that includes an SEP burst, the flux can increase by orders of magnitude. Areas within ISS provide shielding that can keep the total dose within safe limits. For the Space Shuttle, such an event would have required immediate mission termination.

Spacecraft signals
The ionosphere bends radio waves in the same manner that water in a pool bends visible light. When the medium through which such waves travel is disturbed, the light image or radio information is distorted and can become unrecognizable. The degree of distortion (scintillation) of a radio wave by the ionosphere depends on the signal frequency. Radio signals in the VHF band (30 to 300 MHz) can be distorted beyond recognition by a disturbed ionosphere. Radio signals in the UHF band (300 MHz to 3 GHz) transit a disturbed ionosphere, but a receiver may not be able to keep locked to the carrier frequency. GPS uses signals at 1575.42 MHz (L1) and 1227.6 MHz (L2) that can be distorted by a disturbed ionosphere. Space weather events that corrupt GPS signals can significantly impact society. For example, the Wide Area Augmentation System operated by the US Federal Aviation Administration (FAA) is used as a navigation tool for North American commercial aviation. It is disabled by every major space weather event. Outages can range from minutes to days. Major space weather events can push the disturbed polar ionosphere 10° to 30° of latitude toward the equator and can cause large ionospheric gradients (changes in density over distance of hundreds of km) at mid and low latitude. Both of these factors can distort GPS signals.

Long-distance radio signals
Radio waves in the HF band (3 to 30 MHz) (also known as the shortwave band) are reflected by the ionosphere. Since the ground also reflects HF waves, a signal can be transmitted around the curvature of the Earth beyond the line of sight. During the 20th century, HF communications was the only method for a ship or aircraft far from land or a base station to communicate. The advent of systems such as Iridium brought other methods of communications, but HF remains critical for vessels that do not carry the newer equipment and as a critical backup system for others. Space weather events can create irregularities in the ionosphere that scatter HF signals instead of reflecting them, preventing HF communications. At auroral and polar latitudes, small space weather events that occur frequently disrupt HF communications. At mid-latitudes, HF communications are disrupted by solar radio bursts, by X-rays from solar flares (which enhance and disturb the ionospheric D-layer) and by TEC enhancements and irregularities during major geomagnetic storms.

Transpolar airline routes are particularly sensitive to space weather, in part because Federal Aviation Regulations require reliable communication over the entire flight. Diverting such a flight is estimated to cost about $100,000.

Humans in commercial aviation
The magnetosphere guides cosmic ray and solar energetic particles to polar latitudes, while high-energy charged particles enter the mesosphere, stratosphere, and troposphere. These energetic particles at the top of the atmosphere shatter atmospheric atoms and molecules, creating harmful lower-energy particles that penetrate deep into the atmosphere and create measurable radiation. All aircraft flying above 8 km (26,200 feet) altitude are exposed to these particles. The dose exposure is greater in polar regions than at midlatitude and equatorial regions. Many commercial aircraft fly over the polar region. When a space weather event causes radiation exposure to exceed the safe level set by aviation authorities, the aircraft's flight path is diverted.

Measurements of the radiation environment at commercial aircraft altitudes above 8 km (26,000 ft) have historically been done by instruments that record the data on board where the data are then processed later on the ground. However, a system of real-time radiation measurements on-board aircraft has been developed through the NASA Automated Radiation Measurements for Aerospace Safety (ARMAS) program. ARMAS has flown hundreds of flights since 2013, mostly on research aircraft, and sent the data to the ground through Iridium satellite links. The eventual goal of these types of measurements is to data assimilate them into physics-based global radiation models, e.g., NASA's Nowcast of Atmospheric Ionizing Radiation System (NAIRAS), so as to provide the weather of the radiation environment rather than the climatology.

Ground-induced electric fields
Magnetic storm activity can induce geoelectric fields in the Earth's conducting lithosphere. Corresponding voltage differentials can find their way into electric power grids through ground connections, driving uncontrolled electric currents that interfere with grid operation, damage transformers, trip protective relays, and sometimes cause blackouts. This complicated chain of causes and effects was demonstrated during the magnetic storm of March 1989, which caused the complete collapse of the Hydro-Québec electric-power grid in Canada, temporarily leaving nine million people without electricity. The possible occurrence of an even more intense storm led to operational standards intended to mitigate induction-hazard risks, while reinsurance companies commissioned revised risk assessments.

Geophysical exploration
Air- and ship-borne magnetic surveys can be affected by rapid magnetic field variations during geomagnetic storms. Such storms cause data-interpretation problems because the space weather-related magnetic field changes are similar in magnitude to those of the subsurface crustal magnetic field in the survey area. Accurate geomagnetic storm warnings, including an assessment of storm magnitude and duration, allows for an economic use of survey equipment.

Geophysics and hydrocarbon production
For economic and other reasons, oil and gas production often involves horizontal drilling of well paths many kilometers from a single wellhead. Accuracy requirements are strict, due to target size – reservoirs may only be a few tens to hundreds of meters across – and safety, because of the proximity of other boreholes. The most accurate gyroscopic method is expensive, since it can stop drilling for hours. An alternative is to use a magnetic survey, which enables measurement while drilling (MWD). Near real-time magnetic data can be used to correct drilling direction. Magnetic data and space weather forecasts can help to clarify unknown sources of drilling error.

Terrestrial weather
The amount of energy entering the troposphere and stratosphere from space weather phenomena is trivial compared to the solar insolation in the visible and infrared portions of the solar electromagnetic spectrum. Although some linkage between the 11-year sunspot cycle and the Earth's climate has been claimed., this has never been verified. For example, the Maunder minimum, a 70-year period almost devoid of sunspots, has often been suggested to be correlated to a cooler climate, but these correlations have disappeared after deeper studies. The suggested link from changes in cosmic-ray flux causing changes in the amount of cloud formation did not survive scientific tests. Another suggestion, that variations in the extreme ultraviolet (EUV) flux subtly influence existing drivers of the climate and tip the balance between El Niño/La Niña events collapsed when new research showed this was not possible. As such, a linkage between space weather and the climate has not been demonstrated.

In addition, a link has been suggested between high energy charged particles (such as SEPs and cosmic rays) and cloud formation. This is because charged particles interact with the atmosphere to produce volatiles which then condense, creating cloud seeds. This is a topic of ongoing research at CERN, where experiments test the effect of high-energy charged particles on atmosphere. If proven, this may suggest a link between space weather (in the form of solar particle events) and cloud formation.

Most recently, a statistical connection has been reported between the occurrence of heavy floods and the arrivals of high-speed solar wind streams (HSSs). The enhanced auroral energy deposition during HSSs is suggested as a mechanism for the generation of downward propagating atmospheric gravity waves (AGWs). As AGWs reach lower atmosphere, they may excite the conditional instability in the troposphere, thus leading to excessive rainfall.

Observation
Observation of space weather is done both for scientific research and applications. Scientific observation has evolved with the state of knowledge, while application-related observation expanded with the ability to exploit such data.

Ground-based
Space weather is monitored at ground level by observing changes in the Earth's magnetic field over periods of seconds to days, by observing the surface of the Sun, and by observing radio noise created in the Sun's atmosphere.

The Sunspot Number (SSN) is the number of sunspots on the Sun's photosphere in visible light on the side of the Sun visible to an Earth observer. The number and total area of sunspots are related to the brightness of the Sun in the EUV and X-ray portions of the solar spectrum and to solar activity such as solar flares and coronal mass ejections.

The 10.7 cm radio flux (F10.7) is a measurement of RF emissions from the Sun and is roughly correlated with the solar EUV flux. Since this RF emission is easily obtained from the ground and EUV flux is not, this value has been measured and disseminated continuously since 1947. The world standard measurements are made by the Dominion Radio Astrophysical Observatory at Penticton, BC, Canada and reported once a day at local noon in solar flux units (10−22W·m−2·Hz−1). F10.7 is archived by the National Geophysical Data Center.

Fundamental space weather monitoring data are provided by ground-based magnetometers and magnetic observatories. Magnetic storms were first discovered by ground-based measurement of occasional magnetic disturbance. Ground magnetometer data provide real-time situational awareness for postevent analysis. Magnetic observatories have been in continuous operations for decades to centuries, providing data to inform studies of long-term changes in space climatology.

Disturbance storm time index (Dst index) is an estimate of the magnetic field change at the Earth's magnetic equator due to a ring of electric current at and just earthward of the geosynchronous orbit. The index is based on data from four ground-based magnetic observatories between 21° and 33° magnetic latitude during a one-hour period. Stations closer to the magnetic equator are not used due to ionospheric effects. The Dst index is compiled and archived by the World Data Center for Geomagnetism, Kyoto.

Kp/ap index: 'a' is an index created from the geomagnetic disturbance at one midlatitude (40° to 50° latitude) geomagnetic observatory during a 3-hour period. 'K' is the quasilogarithmic counterpart of the 'a' index. Kp and ap are the average of K and an over 13 geomagnetic observatories to represent planetary-wide geomagnetic disturbances. The Kp/ap index indicates both geomagnetic storms and substorms (auroral disturbance). Kp/ap data are available from 1932 onward.

AE index is compiled from geomagnetic disturbances at 12 geomagnetic observatories in and near the auroral zones and is recorded at 1-minute intervals. The public AE index is available with a lag of two to three days that limits its utility for space weather applications. The AE index indicates the intensity of geomagnetic substorms except during a major geomagnetic storm when the auroral zones expand equatorward from the observatories.

Radio noise bursts are reported by the Radio Solar Telescope Network to the U.S. Air Force and to NOAA. The radio bursts are associated with solar flare plasma that interacts with the ambient solar atmosphere.

The Sun's photosphere is observed continuously for activity that can be the precursors to solar flares and CMEs. The Global Oscillation Network Group (GONG) project monitors both the surface and the interior of the Sun by using helioseismology, the study of sound waves propagating through the Sun and observed as ripples on the solar surface. GONG can detect sunspot groups on the far side of the Sun. This ability has recently been verified by visual observations from the STEREO spacecraft.

Neutron monitors on the ground indirectly monitor cosmic rays from the Sun and galactic sources. When cosmic rays interact with the atmosphere, atomic interactions occur that cause a shower of lower-energy particles to descend into the atmosphere and to ground level. The presence of cosmic rays in the near-Earth space environment can be detected by monitoring high-energy neutrons at ground level. Small fluxes of cosmic rays are present continuously. Large fluxes are produced by the Sun during events related to energetic solar flares.

Total Electron Content (TEC) is a measure of the ionosphere over a given location. TEC is the number of electrons in a column one meter square from the base of the ionosphere (around 90 km altitude) to the top of the ionosphere (around 1000 km altitude). Many TEC measurements are made by monitoring the two frequencies transmitted by GPS spacecraft. Presently, GPS TEC is monitored and distributed in real time from more than 360 stations maintained by agencies in many countries.

Geoeffectiveness is a measure of how strongly space weather magnetic fields, such as coronal mass ejections, couple with the Earth's magnetic field. This is determined by the direction of the magnetic field held within the plasma that originates from the Sun. New techniques measuring Faraday rotation in radio waves are in development to measure field direction.

Satellite-based
A host of research spacecraft have explored space weather. The Orbiting Geophysical Observatory series were among the first spacecraft with the mission of analyzing the space environment. Recent spacecraft include the NASA-ESA Solar-Terrestrial Relations Observatory (STEREO) pair of spacecraft launched in 2006 into solar orbit and the Van Allen Probes, launched in 2012 into a highly elliptical Earth orbit. The two STEREO spacecraft drift away from the Earth by about 22° per year, one leading and the other trailing the Earth in its orbit. Together they compile information about the solar surface and atmosphere in three dimensions. The Van Allen probes record detailed information about the radiation belts, geomagnetic storms, and the relationship between the two.

Some spacecraft with other primary missions have carried auxiliary instruments for solar observation. Among the earliest such spacecraft were the Applications Technology Satellite (ATS) series at GEO that were precursors to the modern Geostationary Operational Environmental Satellite (GOES) weather satellite and many communication satellites. The ATS spacecraft carried environmental particle sensors as auxiliary payloads and had their navigational magnetic field sensor used for sensing the environment.

Many of the early instruments were research spacecraft that were re-purposed for space weather applications. One of the first of these was the IMP-8 (Interplanetary Monitoring Platform). It orbited the Earth at 35 Earth radii and observed the solar wind for two-thirds of its 12-day orbits from 1973 to 2006. Since the solar wind carries disturbances that affect the magnetosphere and ionosphere, IMP-8 demonstrated the utility of continuous solar wind monitoring. IMP-8 was followed by ISEE-3, which was placed near the Sun-Earth Lagrangian point, 235 Earth radii above the surface (about 1.5 million km, or 924,000 miles) and continuously monitored the solar wind from 1978 to 1982. The next spacecraft to monitor the solar wind at the point was WIND from 1994 to 1998. After April 1998, the WIND spacecraft orbit was changed to circle the Earth and occasionally pass the point. The NASA Advanced Composition Explorer has monitored the solar wind at the  point from 1997 to present.

In addition to monitoring the solar wind, monitoring the Sun is important to space weather. Because the solar EUV cannot be monitored from the ground, the joint NASA-ESA Solar and Heliospheric Observatory (SOHO) spacecraft was launched and has provided solar EUV images beginning in 1995. SOHO is a main source of near-real time solar data for both research and space weather prediction and inspired the STEREO mission. The Yohkoh spacecraft at LEO observed the Sun from 1991 to 2001 in the X-ray portion of the solar spectrum and was useful for both research and space weather prediction. Data from Yohkoh inspired the Solar X-ray Imager on GOES.

Spacecraft with instruments whose primary purpose is to provide data for space weather predictions and applications include the Geostationary Operational Environmental Satellite (GOES) series of spacecraft, the POES series, the DMSP series, and the Meteosat series. The GOES spacecraft have carried an X-ray sensor (XRS) which measures the flux from the whole solar disk in two bands – 0.05 to 0.4 nm and 0.1 to 0.8 nm – since 1974, an X-ray imager (SXI) since 2004, a magnetometer which measures the distortions of the Earth's magnetic field due to space weather, a whole disk EUV sensor since 2004, and particle sensors (EPS/HEPAD) which measure ions and electrons in the energy range of 50 keV to 500 MeV. Starting sometime after 2015, the GOES-R generation of GOES spacecraft will replace the SXI with a solar EUV image (SUVI) similar to the one on SOHO and STEREO and the particle sensor will be augmented with a component to extend the energy range down to 30 eV.

The Deep Space Climate Observatory (DSCOVR) satellite is a NOAA Earth observation and space weather satellite that launched in February 2015. Among its features is advance warning of coronal mass ejections.

Models
Space weather models are simulations of the space weather environment. Models use sets of mathematical equations to describe physical processes.

These models take a limited data set and attempt to describe all or part of the space weather environment in or to predict how weather evolves over time. Early models were heuristic; i.e.,  they did not directly employ physics. These models take less resources than their more sophisticated descendants.

Later models use physics to account for as many phenomena as possible. No model can yet reliably predict the environment from the surface of the Sun to the bottom of the Earth's ionosphere. Space weather models differ from meteorological models in that the amount of input is vastly smaller.

A significant portion of space weather model research and development in the past two decades has been done as part of the Geospace Environmental Model (GEM) program of the National Science Foundation. The two major modeling centers are the Center for Space Environment Modeling (CSEM) and the Center for Integrated Space weather Modeling (CISM). The Community Coordinated Modeling Center (CCMC) at the NASA Goddard Space Flight Center is a facility for coordinating the development and testing of research models, for improving and preparing models for use in space weather prediction and application.

Modeling techniques include (a) magnetohydrodynamics, in which the environment is treated as a fluid, (b) particle in cell, in which non-fluid interactions are handled within a cell and then cells are connected to describe the environment, (c) first principles, in which physical processes are in balance (or equilibrium) with one another, (d) semi-static modeling, in which a statistical or empirical relationship is described, or a combination of multiple methods.

Commercial space weather development
During the first decade of the 21st Century, a commercial sector emerged that engaged in space weather, serving agency, academia, commercial and consumer sectors. Space weather providers are typically smaller companies, or small divisions within a larger company, that provide space weather data, models, derivative products and service distribution.

The commercial sector includes scientific and engineering researchers as well as users. Activities are primarily directed toward the impacts of space weather upon technology. These include, for example:

Many of these disturbances result in societal impacts that account for a significant part of the national GDP.
 * Atmospheric drag on LEO satellites caused by energy inputs into the thermosphere from solar UV, FUV, Lyman-alpha, EUV, XUV, X-ray, and gamma ray photons as well as by charged particle precipitation and Joule heating at high latitudes;
 * Surface and internal charging from increased energetic particle fluxes, leading to effects such as discharges, single event upsets and latch-up, on LEO to GEO satellites;
 * Disrupted GPS signals caused by ionospheric scintillation leading to increased uncertainty in navigation systems such as aviation's Wide Area Augmentation System (WAAS);
 * Lost HF, UHF and L-band radio communications due to ionosphere scintillation, solar flares and geomagnetic storms;
 * Increased radiation to human tissue and avionics from galactic cosmic rays SEP, especially during large solar flares, and possibly bremsstrahlung gamma-rays produced by precipitating radiation belt energetic electrons at altitudes above 8 km;
 * Increased inaccuracy in surveying and oil/gas exploration that uses the Earth's main magnetic field when it is disturbed by geomagnetic storms;
 * Loss of power transmission from GIC surges in the electrical power grid and transformer shutdowns during large geomagnetic storms.

The concept of incentivizing commercial space weather was first suggested by the idea of a Space Weather Economic Innovation Zone discussed by the American Commercial Space Weather Association (ACSWA) in 2015. The establishment of this economic innovation zone would encourage expanded economic activity developing applications to manage the risks space weather and would encourage broader research activities related to space weather by universities. It could encourage U.S. business investment in space weather services and products. It promoted the support of U.S. business innovation in space weather services and products by requiring U.S. government purchases of U.S. built commercial hardware, software, and associated products and services where no suitable government capability pre-exists. It also promoted U.S. built commercial hardware, software, and associated products and services sales to international partners. designate U.S. built commercial hardware, services, and products as “Space Weather Economic Innovation Zone” activities; Finally, it recommended that U.S. built commercial hardware, services, and products be tracked as Space Weather Economic Innovation Zone contributions within agency reports. In 2015 the U.S. Congress bill HR1561 provided groundwork where social and environmental impacts from a Space Weather Economic Innovation Zone could be far-reaching. In 2016, the Space Weather Research and Forecasting Act (S. 2817) was introduced to build on that legacy. Later, in 2017-2018 the HR3086 Bill took these concepts, included the breadth of material from parallel agency studies as part of the OSTP-sponsored Space Weather Action Program (SWAP), and with bicameral and bipartisan support the 116th Congress (2019) is considering passage of the Space Weather Coordination Act (S141, 115th Congress).

American Commercial Space Weather Association
On April 29, 2010, the commercial space weather community created the American Commercial Space Weather Association (ACSWA) an industry association. ACSWA promotes space weather risk mitigation for national infrastructure, economic strength and national security. It seeks to:

 * provide quality space weather data and services to help mitigate risks to technology;
 * provide advisory services to government agencies;
 * provide guidance on the best task division between commercial providers and government agencies;
 * represent the interests of commercial providers;
 * represent commercial capabilities in the national and international arena;
 * develop best-practices.

A summary of the broad technical capabilities in space weather that are available from the association can be found on their web site http://www.acswa.us.

Notable events

 * On December 21, 1806, Alexander von Humboldt observed that his compass had become erratic during a bright auroral event.
 * The Solar storm of 1859 (Carrington Event) caused widespread disruption of telegraph service.
 * The Aurora of November 17, 1882 disrupted telegraph service.
 * The May 1921 geomagnetic storm, one of the largest geomagnetic storms disrupted telegraph service and damaged electrical equipment worldwide.
 * The Solar storm of August 1972, a large SEP event occurred. If astronauts had been in space at the time, the dose could have been life-threatening.
 * The March 1989 geomagnetic storm included multiple space weather effects: SEP, CME, Forbush decrease, ground level enhancement, geomagnetic storm, etc..
 * The 2000 Bastille Day event coincided with exceptionally bright aurora.
 * April 21, 2002, the Nozomi Mars Probe was hit by a large SEP event that caused large-scale failure. The mission, which was already about 3 years behind schedule, was abandoned in December 2003.
 * The 2003 Halloween solar storms, a series of coronal mass ejections and solar flares in late October and early November 2003 with associated impacts.

General bibliography

 * Daglis, Ioannis A.: Effects of Space Weather on Technology Infrastructure. Springer, Dordrecht 2005, ISBN 1-4020-2748-6.
 * Lilensten, Jean, and Jean Bornarel, Space Weather, Environment and Societies, Springer, ISBN 978-1-4020-4331-4.
 * Moldwin, Mark: An Introduction to Space Weather. Cambridge Univ. Press, Cambridge 2008, ISBN 978-0-521-86149-6.
 * Schwenn, Rainer, Space Weather, Living Reviews in Solar Physics 3, (2006), 2, online article.

Real-time space weather forecast

 * Utah State Univ SWC Real-time GAIM Ionosphere – (real-time model of ionosphere)
 * Space Weather and Radio Propagation. Live and historical data and images with a perspective on how it affects radio propagation
 * Latest Data from STEREO, HINODE and SDO (Large bandwidth)
 * Utah State Univ SWC Real-time GAIM Ionosphere – (real-time model of ionosphere)
 * Space Weather and Radio Propagation. Live and historical data and images with a perspective on how it affects radio propagation
 * Latest Data from STEREO, HINODE and SDO (Large bandwidth)

Other links

 * Space Weather FX – Video podcast series on Space Weather from MIT Haystack Observatory
 * ESA's Space Weather Site
 * Space Weather European Network – (ESA)
 * Q-Up Now (Q-up)
 * Space Weather For Today and Tomorrow (SWFTT)
 * Space Weather Today – Space Weather from Russian Institute for Applied Geophysics
 * Q-Up Now (Q-up)
 * Space Weather For Today and Tomorrow (SWFTT)
 * Space Weather Today – Space Weather from Russian Institute for Applied Geophysics
 * Q-Up Now (Q-up)
 * Space Weather For Today and Tomorrow (SWFTT)
 * Space Weather Today – Space Weather from Russian Institute for Applied Geophysics
 * Q-Up Now (Q-up)
 * Space Weather For Today and Tomorrow (SWFTT)
 * Space Weather Today – Space Weather from Russian Institute for Applied Geophysics
 * Space Weather For Today and Tomorrow (SWFTT)
 * Space Weather Today – Space Weather from Russian Institute for Applied Geophysics
 * Space Weather For Today and Tomorrow (SWFTT)
 * Space Weather Today – Space Weather from Russian Institute for Applied Geophysics
 * Space Weather Today – Space Weather from Russian Institute for Applied Geophysics
 * Space Weather Today – Space Weather from Russian Institute for Applied Geophysics
 * Space Weather Today – Space Weather from Russian Institute for Applied Geophysics
 * Space Weather Today – Space Weather from Russian Institute for Applied Geophysics

title: Space weather


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Aestivation

Aestivation (aestas (summer); also spelled estivation in American English) is a state of animal dormancy, similar to hibernation, although taking place in the summer rather than the winter. Aestivation is characterized by inactivity and a lowered metabolic rate, that is entered in response to high temperatures and arid conditions. It takes place during times of heat and dryness, which are often the summer months.

Invertebrate and vertebrate animals are known to enter this state to avoid damage from high temperatures and the risk of desiccation. Both terrestrial and aquatic animals undergo aestivation. Fossil records suggest that aestivation may have evolved several hundred million years ago.

Physiology
Organisms that aestivate appear to be in a fairly "light" state of dormancy, as their physiological state can be rapidly reversed, and the organism can quickly return to a normal state. A study done on Otala lactea, a snail native to parts of Europe and Northern Africa, shows that they can wake from their dormant state within ten minutes of being introduced to a wetter environment.

The primary physiological and biochemical concerns for an aestivating animal are to conserve energy, retain water in the body, ration the use of stored energy, handle the nitrogenous end products, and stabilize bodily organs, cells, and macromolecules. This can be quite a task as hot temperatures and arid conditions may last for months, in some cases for years. The depression of metabolic rate during aestivation causes a reduction in macromolecule synthesis and degradation. To stabilise the macromolecules, aestivators will enhance antioxidant defenses and elevate chaperone proteins. This is a widely used strategy across all forms of hypometabolism. These physiological and biochemical concerns appear to be the core elements of hypometabolism throughout the animal kingdom. In other words, animals which aestivate appear to go through nearly the same physiological processes as animals that hibernate.

Mollusca
Gastropoda: some air-breathing land snails, including species in the genera Helix, Cernuella, Theba, Helicella, Achatina and Otala, commonly aestivate during periods of heat. Some species move into shaded vegetation or rubble. Others climb up tall plants, including crop species as well as bushes and trees, and will also climb human-made structures such as posts, fences, etc.

Their habit of climbing vegetation to aestivate has caused more than one introduced snail species to be declared an agricultural nuisance.

To seal the opening to their shell to prevent water loss, pulmonate land snails secrete a membrane of dried mucus called an epiphragm. In certain species, such as Helix pomatia, this barrier is reinforced with calcium carbonate, and thus it superficially resembles an operculum, except that it has a tiny hole to allow some oxygen exchange.

There is a decrease in metabolic rate and reduced rate of water loss in aestivating snails like Rhagada tescorum, Sphincterochila boissieri and others.

Arthropoda
Insecta: Lady beetles (Coccinellidae) have been reported to aestivate. Another type of beetle (Blepharida rhois) also chooses to aestivate. They usually do so when the temperature is warmer and will re-emerge in the late summer or early fall. Mosquitoes also are reported to undergo aestivation. False honey ants are well known for being winter active and aestivate in temperate climates. Bogong moths will aestivate over the summer to avoid the heat and lack of food sources. Adult alfalfa weevils (Hypera postica) aestivate during the summer in the southeastern United States, during which their metabolism, respiration, and nervous systems show a dampening of activity.

Crustacea: An example of a crustacean undergoing aestivation is with the Australian crab Austrothelphusa transversa , which undergoes aestivation underground during the dry season.

Reptiles and amphibians
Non-mammalian animals that aestivate include North American desert tortoises, crocodiles, and salamanders. Some amphibians (e.g. the cane toad and greater siren) aestivate during the hot dry season by moving underground where it is cooler and more humid. The California red-legged frog may aestivate to conserve energy when its food and water supply is low.

The water-holding frog has an aestivation cycle. It buries itself in sandy ground in a secreted, water-tight mucus cocoon during periods of hot, dry weather. Australian Aboriginals discovered a means to take advantage of this by digging up one of these frogs and squeezing it, causing the frog to empty its bladder. This dilute urine—up to half a glassful—can be drunk. However, this will cause the death of the frog which will be unable to survive until the next rainy season without the water it had stored.

The western swamp turtle aestivates to survive hot summers in the ephemeral swamps it lives in. It buries itself in various media which change depending on location and available substrates. Because the species is critically endangered, the Perth Zoo began a conservation and breeding program for it. However, zookeepers were unaware of the importance of their aestivation cycle and during the first summer period would perform weekly checks on the animals. This repeated disturbance was detrimental to the health of the animals, with many losing significant weight and some dying. The zookeepers quickly changed their procedures and now leave their captive turtles undisturbed during their aestivation period.

Fish
African lungfish also aestivate as can salamanderfish.

Mammals
Although relatively uncommon, a small number of mammals aestivate. Animal physiologist Kathrin Dausmann of Philipps University of Marburg, Germany, and coworkers presented evidence in a 2004 edition of Nature that the Malagasy fat-tailed dwarf lemur hibernates or aestivates in a small tree hole for seven months of the year. According to the Oakland Zoo in California, four-toed hedgehogs are thought to aestivate during the dry season.

title: Aestivation


text:
Conjunction (grammar)

In grammar, a conjunction (abbreviated or ) is a part of speech that connects words, phrases, or clauses that are called the conjuncts of the conjunctions. That definition may overlap with that of other parts of speech, and so what constitutes a "conjunction" must be defined for each language. In English, a given word may have several senses, and be either a preposition or a conjunction depending on the syntax of the sentence. For example, after is a preposition in "he left after the fight" but is a conjunction in "he left after they fought". In general, a conjunction is an invariable (non-inflected) grammatical particle that may or may not stand between the items conjoined.

The definition of conjunction may also be extended to idiomatic phrases that behave as a unit with the same function, e.g. "as well as", "provided that".

A simple literary example of a conjunction is "the truth of nature, and the power of giving interest" (Samuel Taylor Coleridge's Biographia Literaria).

A conjunction may be placed at the beginning of a sentence: "But some superstition about the practice persists."

Separation of clauses
Commas are often used to separate clauses. In English, a comma is used to separate a dependent clause from the independent clause if the dependent clause comes first: After I fed the cat, I brushed my clothes. (Compare this with I brushed my clothes after I fed the cat.) A relative clause takes commas if it is non-restrictive, as in I cut down all the trees, which were over six feet tall. (Without the comma, this would mean that only the trees more than six feet tall were cut down.) Some style guides prescribe that two independent clauses joined by a coordinating conjunction (for, and, nor, but, or, yet, so) must be separated by a comma placed before the conjunction. In the following sentences, where the second clause is independent (because it can stand alone as a sentence), the comma is considered by those guides to be necessary: In the following sentences, where the second half of the sentence is not an independent clause (because it does not contain an explicit subject), those guides prescribe that the comma be omitted: However, such guides permit the comma to be omitted if the second independent clause is very short, typically when the second independent clause is an imperative, as in: The above guidance is not universally accepted or applied. Long coordinate clauses are nonetheless usually separated by commas:
 * Mary walked to the party, but she was unable to walk home.
 * Designer clothes are silly, and I can't afford them anyway.
 * Don't push that button, or twelve tons of high explosives will go off right under our feet!
 * Mary walked to the party but was unable to walk home.
 * I think designer clothes are silly and can't afford them anyway.
 * Sit down and shut up.
 * She had very little to live on, but she would never have dreamed of taking what was not hers.

A comma between clauses may change the connotation, reducing or eliminating ambiguity. In the following examples, the thing in the first sentence that is very relaxing is the cool day, whereas in the second sentence it is the walk, since the introduction of commas makes "on a cool day" parenthetical:

 * They took a walk on a cool day that was very relaxing.

 * They took a walk, on a cool day, that was very relaxing.

If another prepositional phrase is introduced, ambiguity increases, but when commas separate each clause and phrase, the restrictive clause can remain a modifier of the walk:

 * They took a walk in the park on a cool day that was very relaxing.

 * They took a walk, in the park, on a cool day, that was very relaxing.

In some languages, such as German and Polish, stricter rules apply on comma use between clauses, with dependent clauses always being set off with commas, and commas being generally proscribed before certain coordinating conjunctions.

The joining of two independent sentences with a comma and no conjunction (as in "It is nearly half past five, we cannot reach town before dark.") is known as a comma splice and is sometimes considered an error in English; in most cases a semicolon should be used instead. A comma splice should not be confused, though, with the literary device called asyndeton, in which coordinating conjunctions are purposely omitted for a specific stylistic effect.

Etymology
Beginning in the 17th century, an element of a conjunction was known as a conjunct. A conjunction itself was then called a connective. That archaic term, however, diminished in usage during the early 20th century. In its place, the terms coordinating conjunction (coined in the mid-19th century) and correlative conjunction (coined in the early 19th century) became more commonly used.

Coordinating conjunctions
Coordinating conjunctions, also called coordinators, are conjunctions that join, or coordinate, two or more items (such as words, main clauses, or sentences) of equal syntactic importance. In English, the mnemonic acronym FANBOYS can be used to remember the most commonly used coordinators: for, and, nor, but, or, yet, and so. These are not the only coordinating conjunctions; various others are used, including: "and nor" (British), "but nor" (British), "neither" ("They don't gamble, neither do they smoke"), "no more" ("They don't gamble, no more do they smoke"), and "only" ("I would go, only I don't have time"). Types of coordinating conjunctions include cumulative conjunctions, adversative conjunctions, alternative conjunctions, and illative conjunctions.

Here are some examples of coordinating conjunctions in English and what they do:

 * For – an illative (i.e. inferential), presents rationale ("They do not gamble or smoke, for they are ascetics.")
 * And – a cumulative, adds non-contrasting items or ideas ("They gamble, and they smoke.")
 * Nor – presents an alternative non-contrasting (also negative) idea ("They do not gamble, nor do they smoke.")
 * But – an adversative, presents a contrast or exception ("They gamble, but they don't smoke.")
 * Or – presents an alternative non-contrasting item or idea ("Every day they gamble, or they smoke.")
 * Yet – an adversative, presents a strong contrast or exception ("They gamble, yet they don't smoke.")
 * So – an illative (i.e. inferential), presents a consequence ("He gambled well last night, so he smoked a cigar to celebrate.")

Only and, or, nor are actual coordinating logical operators connecting atomic propositions or syntactic multiple units of the same type (subject, objects, predicative, attributive expressions, etc.) within a sentence. The cause and consequence (illative) conjunctions are pseudo-coordinators, being expressible as antecedent or consequent to logical implications or grammatically as subordinate conditional clauses.

Correlative conjunctions
Correlative conjunctions are pairs of conjunctions that join two or more correlated lexical items within a sentence. There are many different pairs of correlative conjunctions:

 * either...or
 * not only...but (also)
 * neither...nor
 * both...and
 * whether...or
 * just as...so
 * the...the
 * as...as
 * as much...as
 * no sooner...than
 * rather...than
 * not...but rather

Examples:

 * You either do your work or prepare for a trip to the office. (Either do or prepare)
 * He is not only handsome but also brilliant. (Not only A but also B)
 * Neither the basketball team nor the football team is doing well.
 * Both the cross-country team and the swimming team are doing well.
 * You must decide whether you stay or you go.
 * Just as many Americans love basketball, so many Canadians love ice hockey.
 * The more you practice dribbling, the better you will be at it.
 * Football is as fast as hockey (is (fast)).
 * Football is as much an addiction as it is a sport.
 * No sooner did she learn to ski than the snow began to thaw.
 * I would rather swim than surf.
 * He donated money not to those in need, but rather to those who would benefit him.

Conjunctions of time
Examples:

Subordinating conjunctions
Subordinating conjunctions, also called subordinators, are conjunctions that introduce content, relative, and adverbial clauses as dependent clauses, and join them to other clauses, either independent or dependent clauses. The most common subordinating conjunctions in the English language include after, although, as, as far as, as if, as long as, as soon as, as though, because, before, even if, even though, every time, if, in order that, since, so, so that, than, that, though, unless, until, when, whenever, where, whereas, wherever, and while. Complementizers can be considered to be special subordinating conjunctions that introduce content clauses (complements of the verb phrase): e.g. "I wonder whether he'll be late. I hope that he'll be on time". Some subordinating conjunctions, when used to introduce a phrase instead of a full clause, become prepositions with identical meanings. Relativizers are subordinators that introduce relative clauses.

The subordinating conjunction performs two important functions within a sentence: illustrating the importance of the independent clause and providing a transition between two ideas in the same sentence by indicating a time, place, or cause and therefore affecting the relationship between the clauses.

In many verb-final languages, subordinate clauses must precede the main clause on which they depend. The equivalents to the subordinating conjunctions of non-verb-final languages such as English are either
 * clause-final conjunctions (e.g. in Japanese); or
 * suffixes attached to the verb, and not separate words

Such languages often lack conjunctions as a part of speech, because:

 * the form of the verb used is formally nominalised and cannot occur in an independent clause
 * the clause-final conjunction or suffix attached to the verb is a marker of case and is also used in nouns to indicate certain functions. In this sense, the subordinate clauses of these languages have much in common with postpositional phrases.

In other West Germanic languages like German and Dutch, the word order after a subordinating conjunction is different from that in an independent clause, e.g. in Dutch want ('for') is coordinating, but omdat ('because') is subordinating. The clause after the coordinating conjunction has normal word order, but the clause after the subordinating conjunction has verb-final word order. Compare:

 * Hij gaat naar huis, want hij is ziek. ('He goes home, for he is ill.')
 * Hij gaat naar huis, omdat hij ziek is. ('He goes home, because he is ill.')

Similarly, in German, denn ('for') is coordinating, but weil ('because') is subordinating:
 * Er geht nach Hause, denn er ist krank. ('He goes home, for he is ill.')
 * Er geht nach Hause, weil er krank ist. ('He goes home, because he is ill.')

Starting a sentence
It is now generally agreed that a sentence may begin with a coordinating conjunction like and, but, or yet. While some people consider this usage improper, Follett's Modern American Usage labels its prohibition a "supposed rule without foundation" and a "prejudice [that] lingers from a bygone time."

Some associate this belief with their early school days. One conjecture is that it results from young children's being taught to avoid simple sentences starting with and and are encouraged to use more complex structures with subordinating conjunctions. In the words of Bryan A. Garner, the "widespread belief ... that it is an error to begin a sentence with a conjunction such as and, but, or so has no historical or grammatical foundation", and good writers have frequently started sentences with conjunctions.

There is also a misleading guideline that a sentence should never begin with because. Because is a subordinating conjunction, and introduces a dependent clause. It may start a sentence when the main clause follows the dependent clause.

Examples

 * "And now we have Facebook and Twitter and Wordpress and Tumblr and all those other platforms that take our daily doings and transform them into media."
 * "So any modern editor who is not paranoid is a fool".
 * "And strikes are protected globally, existing in many of the countries with labour laws outside the Wagner Act model."

Warlpiri
In Warlpiri, a Pama-Nyungan language spoken in Australia, conjunctions function differently from English or other Germanic languages. In unembedded contexts, Warlpiri uses the coordinator manu, such that P manu Q translates to "P and Q": Cecilia manu Gloriapala yanu tawunu kurra means "Cecilia and Gloria went to town", but in the negative contexts, P manu Q translates to "neither P nor Q", such that kularnangku yinyi rampaku manu loli means "I won't give you cookies or lollipops", as kularnanagku is a form of the Warlpiri negative marker.

title: Conjunction (grammar)


text:
Talk:Conjunction (grammar)

Information at Grammatical particle
Grammatical particle already has some text on conjunctions...maybe merge or move the text from there here or here there? —The preceding unsigned comment was added by DennisDaniels (talk • contribs).

Assorted complaints
If and/or is a disjunction than to say it is a conjunction perhaps isn't fair

In addition it isn't a "english" "part of speech".

—The preceding unsigned comment was added by 66.168.62.46 (talk • contribs).
 * A conjunction is a word that links words, phrases, or clauses. There are three types of conjunctions: coordinating conjunctions, correlative conjunctions, and subordinating conjunctions. Coordinating conjunctions may join single words, or they may join groups of words, but they must always join similar elements: e.g. subject+subject, verb phrase+verb phrase, sentence+sentence. When a coordinating conjunction is used to join elements, the element becomes a compound element. Correlative conjunctions also connect sentence elements of the same kind: however, unlike coordinating conjunctions, correlative conjunctions are always used in pairs. Subordinating conjunctions, the largest class of conjunctions, connect subordinate clauses to a main clause. These conjunctions are adverbs used as conjunctions. —The preceding unsigned comment was added by 216.73.65.55 (talk • contribs).

Hello, and please sign your name from now on with four tildes. In any case, I would like to point out that this article is not entitled "English Conjunctions" but rather "Conjunctions", the cross-linguistic lexcial category. Jamutaq (talk) 21:27, 27 February 2015 (UTC)

"But" vs. "and"
I am seeking the distinction between the conjunctions "but" and "and"... Unfortunately, the site implies they are the same "Coordinating conjunctions...that join two items of equal syntactic importance." I believe there are subtle (and some distinct) differences in the various conjunctions... My current focus is defining the actual or implied differences between the terms "Separate BUT Equal" and "Separate AND Equal" I welcome your thoughts Wikipedia Community. sp8s@msn.com 67.9.104.10 15:08, 11 December 2005 (UTC)
 * I tend to think that "but" joins two generally contrasting ideas, while "and" connects two that are similar. 74.134.139.118 21:08, 30 May 2006 (UTC)Jello
 * You must remember that syntactic importance refers to the "balance" of the elements or clauses in relation to grammar, not to the elements or clauses [meaning] themselves. They are sometimes used differently.

"And" joins two things together into one group. Think "togetherness." :) ->Two syntactically equal people (who are different) who will go to the mall together. ->Three syntactically equal types of clothing (that are different) that will be bought (by a group of people who are shopping together). ->Two syntactically equal clauses that are joined together to show the order of what they will do together.
 * Ex: George and I are going to the mall.
 * Ex: We want to buy shirts, shoes and socks.
 * Ex: We are then going to go to a restaurant and, after that, we plan to see a film.

"But" is used to show contrast. Think "separation" or "difference." -> Two syntactically equal clauses about two people who want to go to different places. -> One clause which is subordinated by another clause about two people who want to go to different places. -> Two syntactically equal items that are not both of interest to the buyer. -> Two syntactically equal clauses that show a series of events, ending in the different movies the two people want to see.
 * Ex: George wants to go to the mall but I want to go to the hardware store.
 * Ex: George, but not I, wants to go to the mall.
 * Ex. He wants to buy shirts but not socks.
 * Ex. After we eat, we are then going to go to the cinema, but George wants to see Star Wars and I want to see Jaws.

"And" is used for both elements and clauses, as well as for ordinating, whereas "but" is usually used for connecting clauses and is not commonly used for connecting elements. ReveurGAM (talk) 08:48, 11 December 2008 (UTC)

For
I think placing for as the first example of a conjunction is very misleading. For is mostly used as a preposition: "He bought flowers for her", etc. The use as a conjunction is limited to quite formal writing: "He gave her the flowers, for he loved her so much." — Adi Japan   ☎  12:50, 14 June 2006 (UTC)
 * How is using for as a conjunction any different to using 'because' which is classed as a subordinating conjunction while for is classed as a coordinating conjunction? I could easily re-write that sentence ""He gave her the flowers, because he loved her so much.". What's the exact difference? (89.241.235.84 18:10, 3 July 2007 (UTC))
 * One indicator — not a perfect one by any stretch — is that so-called "subordinating" conjunctions introduce a subordinate clause, which can be moved to the start of the clause containing them: "He gave her the flowers, because he loved her so much" can be re-written as "Because he loved her so much, he gave her the flowers." For does not have this property; we can say, "He gave her the flowers, for he loved her so much", but not *"For he loved her so much, he gave her the flowers." —RuakhTALK 18:43, 3 July 2007 (UTC)
 * In the first example, shouldn't the comma be omitted? ""He gave her the flowers because he loved her so much" Unimaginative Username (talk) 06:10, 27 November 2007 (UTC)
 * It depends what you're trying to say; if you're answering the question "Why did he give her the flowers?", no comma, but if you're answering a question like "Did he give her the flowers?" or "To whom did he give the flowers?" or "Who gave her the flowers?" or the like, then yes comma. That said, it's not always obvious exactly what implicit question a given sentence is trying to answer — that's just not how language works — so there are many cases where the comma can be present or absent. —Ruakh TALK 21:01, 27 November 2007 (UTC)
 * Very nice distinction! Out of context, it appears not to need the comma, but as you say, if it's adding tangential info... which is what makes copy-editing such a nuanced, fascinating, and time-consuming hobby! Cheers, Unimaginative Username (talk) 00:32, 28 November 2007 (UTC)

"For, yet, so" are not conjunctions
Of these seven words, only "and" and "but" and "or" are fully-satisfactory co-ordinators, though "nor" comes very close. "So" and "yet" are conjunctive adverbs like "however". But the preposition "for" doesn't even resemble any conjunctions (much less any co-ordinating conjunctions) in any way. (Although it can have a clause for its "object" or "complement". --Eldin raigmore (talk) 16:11, 13 March 2010 (UTC)
 * Do you have a source for this statement? I have a college-level grammar textbook published in 2009 that says that they are. Henrymrx (t·c) 22:28, 27 March 2010 (UTC)

 * More than that, Merriam Webster lists 'for' as a conjunction (http://www.merriam-webster.com/dictionary/for). As an editor in the U.S., I know a good deal of us (fans of the AP and Chicago styles among others) use this is our primary source in these matters; I can't speak for an international audience though. —Preceding unsigned comment added by 173.71.64.107 (talk) 14:04, 7 May 2010 (UTC)

 * The assertion that "so", "yet", and "for" are not coordinating conjunctions is incorrect OR. Coordinating conjunctions in English can link main clauses -- clauses that could stand alone as a sentence:

 * A is true, so B is true. / A is true. So B is true.
 * A is not true, yet B is true. / A is not true. Yet B is true.
 * A is true, for B is true. / A is true. For B is true.

 * Furthermore, "so" and "yet" are not conjunctive adverbs like "however". We can punctuate as "A is not true, yet B is true"; but we cannot punctuate as "A is not true, however B is true" (despite the fact that one sometimes sees the latter mistake).

 * I'm removing the OR POV edit of 15:56, 13 March 2010 in this regard. 75.183.96.242 (talk) 21:36, 29 August 2010 (UTC)

List found in comments
I found the following in HTML comments in the article. -- Beland 19:55, 17 June 2006 (UTC)

Should the following be listed anywhere?

 * after
 * although
 * as
 * as far as
 * as if
 * as long as
 * because
 * before
 * even if
 * for
 * how
 * granted (that)
 * if
 * in case
 * lest
 * like
 * on condition that
 * provided
 * providing
 * since
 * so
 * so that
 * supposing
 * than
 * unless
 * until
 * 'til
 * till
 * that
 * though
 * when
 * whence
 * whenever
 * where
 * whereabouts
 * whereafter
 * whereagainst
 * wherealong
 * whereas
 * whereat
 * whereby
 * wherever
 * wherefor
 * wherefrom
 * wherein
 * whereinto
 * whereinsoever
 * whereof
 * whereout
 * whereover
 * whereround
 * whereso
 * wheresoever
 * wheresomever
 * wherethrough
 * wheretill
 * whereunder
 * whereunto
 * whereupon
 * whereup
 * whether
 * while
 * whither

What about "forasmuch" and "inasmuch" ? Gregbard 10:07, 6 September 2007 (UTC)
 * I crossed out words that have since been mentioned on the page. The article does a fine job of including examples of conjunctions, as it's not possible to include every conjunction (otherwise it would be cluttered or look like a list). However, a few common ones like as could be added. The compound words (where+..., forasmuch, inasmuch) are mostly old ways of saying things and not used colloquially, or they are used exclusively in legal mumbo-jumbo.
 * Wikky Horse 02:58, 7 September 2007 (UTC)

 * Someone anonymous edited the paragraph on phrases that can be used as co-ordinating conjunctions to change "provided that" to "providing that". This was a mistake.  The single word "providing" is often so used, as is the two-word phrase "provided that"; but "providing that" is much rarer and is considered awkward by many native speakers of English.  For references, search the web for "providing that". Eldin raigmore (talk) 23:27, 27 December 2011 (UTC)

Examples
It might be prudent to include examples. I am not familiar with the topic to do so and could benefit from them —The preceding unsigned comment was added by Jgassens (talk • -->

BISAWAWE
BISAWAWE is a mnemonic? I feel like I need a mnemonic for the mnemonic. The Internet Anagram Server informs me that "I SAW A WEB" is an anagram of BISAWAWE. If you're feeling bold, substitute that in the article. --DavidConrad 18:59, 1 August 2007 (UTC)

Conjunctions beginning sentences
I removed from this article the straitlaced assertion that sentences should not begin with coordinating conjunctions. It's a kind of polysyndeton, and perfectly acceptable. Vbbdesign (talk) 03:46, 28 June 2008 (UTC)

"not this nor that" = "not this or that" ?
I've seen people say both "or" and "nor" in phrases like that, is it the same thing in those cases? or is one of them the wrong word for the meaning?--TiagoTiago (talk) 13:06, 18 December 2008 (UTC)

Rolled back edit
I rolled back through some edits that had introduced many errors into the page. (Someone thought adding a section on cobjunctions was funny, and someone else had eliminated all the periods and made them "ands" in another section -- this problem had survived a more extensive edit, but I didn't make the effort to combine the two, so if the previous editor wants to take a crack at it, fine by me...)

I also rewrote the section on starting sentences with coordinating conjunctions. It seemed to me to make more sense to frame it as a debate.

Wikinetman (talk) 08:26, 11 March 2009 (UTC)

Search redirect
Could someone enter this article as a search result for "conjunction" when searching from the "search page? THKS. 99.11.160.111 (talk) 10:13, 1 December 2009 (UTC)

why 'but' redirect at top
Why is there is a BUT link at the top of this page? But is no more important a conjunction than any other - I fail to see why it should get a special mention Willphase (talk) 04:24, 17 March 2010 (UTC)

"Whilst" and "now" as coordinating conjunctions
The article currently says "various others [besides the FANBOYS seven] are used as coordinating conjunctions, including whilst and now." (1) I'm not British, so could someone give me an example here of "whilst" being used as a coordinating conjunction, along the lines of this example for "or": "You could go or you could stay." / "You could go. Or you could stay." While the article gives a citation (that I don't have access to), I'm skeptical. (2) I'm extremely skeptical that "now" can be used as a coordinating conjunction. Again, can someone give an example here? 75.183.96.242 (talk) 22:01, 29 August 2010 (UTC)

I've looked up the source given in the article, and here's what I found. It is indeed true that Fowler's Modern English Usage claims that John Algeo (International J. of Lexicography, vol. 1, 1988) states that "whilst" and "now" can be used as coordinating conjunctions. However, the examples that Fowler's gives are of them being used as subordinating conjunctions: "I would like to thank .... for their encouragement whilst I was writing this book." " Now ['Now that' in American English] the socialists have accepted the expensive red rose as their emblem, may I suggest...." Either Fowler's got it wrong and Algeo said they were subordinating conjunctions, or Algeo himself got it wrong-- I don't know which since I cannot get access to that issue of the journal he wrote in. However, I looked in Algeo's subsequent 2006 book ''British or American English? A Handbook of Word and Grammar Patterns (chapter 9 on conjunctions), and I found that both usages are given under subordinating'' conjunctions. So either Fowler's got it wrong about Algeo, or Algeo changed his mind. In any event, "whilst" and "now (that)" are subordinating conjunctions, so I will correct this Wikipedia article accordingly. 75.183.96.242 (talk) 20:23, 1 September 2010 (UTC)

for as a coordinating conjunction
"He is gambling with his health, for he has been smoking far too long.") (though "for" is more commonly used as a preposition)

Isn't this sentence an example of a subordinating conjunction instead? —Preceding unsigned comment added by 212.190.130.3 (talk) 05:42, 30 March 2011 (UTC)

Examples for subordinated conjuncions
There are very clear and helpful examples of coordinating and correlating conjunctions. But when it comes to subordinated conjunctions it drifts off into a discussion of usage in other languages. Similar examples of subordinated conjunctions would be appreciated, and I sugget it would be better to put th eother languages discussion into a section of its own.

Baska436 (talk) 12:01, 21 July 2011 (UTC)

Whether [or not]
I've always wondered whether the use of "or not" in a sentence containing whether is completely superfluous. I hear/read it so often and to my mind it seems wrong. For example - "I haven't decided yet whether or not I'll buy that car", or "I haven't decided whether I'll buy that car or not". Either way, the or not seems pointless. Surely this works on it's own - "I haven't decided yet whether I'll buy that car". It doesn't seem to be lacking an "or not". 84.155.183.98 (talk) 15:56, 4 August 2011 (UTC) DD

Serial comma before 'and'
At the beginning of the article, there is a definition of the 'and' conjunction and the example: "They gamble, and they smoke". The serial comma only gets applied when there is a list of three or more items. It really doesn't get used for simple separation. Shouldn't the example read "They gamble and they smoke"? Sunnyape (talk) 22:52, 15 August 2011 (UTC)

 * This is not an example of a serial comma. It's two independent clauses linked by a conjunction, which strictly speaking typically requires a comma. — 98.203.140.232 (talk) 07:52, 15 December 2011 (UTC)

Contradictory edit in lede
An editor has added (and I have reverted) material to the following sentence in the lede:

 * Many students are taught that certain conjunctions (such as "and", "but", and "so") should not begin sentences, although this belief has "no historical or grammatical foundation".

The added passage was:

 * of course, the conjunction of such a sentence would not be explicitly connecting two grammatical units (words, sentences, phrases or clauses), which provides the logical foundation for avoiding such a construction.

First, the resulting combined passage becomes self-contradictory, with the first half asserting one thing and the second half asserting the opposite. Second, the second half is self-evidently wrong: If a coordinating conjunction appears at the start of one sentence, it links the previous sentence with that sentence. Third, while the existing passage is footnoted to a reputable source, the added material has no source given and thus is WP:Original research, which is not permitted in Wikipedia. Duoduoduo (talk) 15:37, 12 September 2011 (UTC)

"neither", "no more", and "only"
I am not an expert on British English, nor do I have access to the Algeo and Burchfield sources, so I cannot verify the coordinating conjunctions "and nor", "but nor", or "or nor". However, the examples given for "neither", "no more", and "only" are clearly not being used as conjunctions, so I'm removing them (although I'm thinking you might be able to make a case for "neither", just with a better example). Can anyone who does know something about British English verify the other three? (They don't have examples, and they're in the same sentence as the ones which don't belong there, so I'd just like to make sure). --Brjaga (talk) 21:09, 27 September 2011 (UTC)

 * I was the one who put in all of these, about a year ago, after I found them in the indicated sources. I'm pretty sure that the specific examples I gave were drawn from those sources. The ones, with examples, that you've reverted are:

 * "neither" ("They don't gamble; neither do they smoke"), "no more" ("They don't gamble; no more do they smoke"), and "only" ("Can we perform? Only if we practice").

 * Of these, it seems clear to me that "neither" and "no more" are synonyms for "nor" in these sentences; replace them with "nor", and I don't think you'd dispute that "nor" is used there as a coordinating conjunction. I think you're just not familiar with that usage, but I've certainly seen it often enough, and not just in the source given. As for the example with "only", it looks to me like a subordinating conjunction since it's followed by a subordinate clause.

 * So I'm putting back in the "neither" and "no more" examples, which are certainly right. As for the "only" example, I invite further discussion as to whether the source is just wrong or whether there just needs to be a more appropriate example.

 * Also, the "and nor", "but nor", and "or nor" conjunctions are certainly used by the British, so they too should stay. Duoduoduo (talk) 02:19, 28 September 2011 (UTC)

 * Correction: the versions you reverted are not the same as the ones I put in a year ago (given above) -- someone must have messed them up since then. I'll revert to the originals. Duoduoduo (talk) 02:23, 28 September 2011 (UTC)

 * They were messed up on 7 August 2011 by User:MMcLaughlin2097. Thanks for catching it, Brjaga ! Duoduoduo (talk) 02:31, 28 September 2011 (UTC)

 * Sounds like "no more" and "neither" do belong there, but since the parts in question are in the section on Coordinating Conjunctions, I think "only" ought to be moved to the subordinating conjunction section (if it's not already there). I seem to remember at the time that I initially removed these that I thought "only" could be considered one, but I was only looking at whether it belonged in the coordinating conjunction section.--Brjaga (talk) 00:37, 9 October 2011 (UTC)

 * Actually, I somehow missed the new (i.e. original) example for "only", which does seem to be coordinating. Thanks for fixing those examples, and teaching me something about British English. --Brjaga (talk) 00:41, 9 October 2011 (UTC)

Also
Is the word also a necessary part of the correlative conjunction not only...but also?? I'm sure the following statement is valid:

Wikipedia has articles not only in English but in hundreds of languages.

There's no also in the above statement. Georgia guy (talk) 22:57, 21 September 2012 (UTC)
 * Sorry it's taken nine years to reply, but also isn't essential to the not only...but also phrase, which I refuse to identify as a correlative conjunction. Consider how "but" is the only conjunction in that phrase whereas not, only, and also are adverbs. Originally, correlative conjunctions applied only to two conjunctions that operated in pairs:
 * "I'm right whether you agree or you disagree.
 * Subsequently, various misguided linguists misapplied the correlative conjunction term to bifurcated phrases that include only one conjunction:
 * "Neither a borrower nor a lender be." (Here, "neither" is an  ADV .)
 * "Both the cross country team and the swimming team are doing well." (Here, "both" is an  ADV .)
 * "Football is as fast as hockey." (Here, the first "as" is an  ADV .)
 * Most recently, crackpot linguist wannabes have maintained that phrases without any conjunction whatsoever are somehow correlative conjunctions:
 * "Just as many Americans love basketball, so many Canadians love ice hockey." ("as" and "so" are  ADVs .)
 * "The more you practice dribbling, the better you will be at it." ("The" is always a  DTRM .)
 * Why don't I fix the article accordingly? I don't see the point in swimming solo against the tide to save a ship that's already sunk and wrecked nearly beyond recognition. --Kent Dominic·(talk) 01:47, 25 June 2021 (UTC)

Additional infobyte
Regards to this: 'Many students are taught that certain conjunctions (such as "and", "but", "because", and "so") should not begin sentences; although authorities such as the Chicago Manual of Style state that this teaching has "no historical or grammatical foundation".'

I actually speak Old English, and I have read historical Old English texts where conjunctions are used at the beginning of a sentence, so the practice has a long history (at least 1000+ years). Should this additional little bit of information be included. Gott wisst (talk) 04:17, 9 May 2013 (UTC)

Specific Concern
Dear Wikipedia Users, Have any of you noticed the fact that grammatical conjunctions have been used in the article itself (more specifically, the first paragraph)? Should it be changed to have no grammatical conjunctions before it has been explained? Your thoughts, please. Abdullah H. Mirza (talk) 19:18, 21 May 2013 (UTC)

To add to this, 'Microsoft Word' has a comma before a conjuction as a grammatical error: "If you are using a conjunction to connect only two items, it is incorrect to use a comma before the conjunction." See the sentence "In general, a conjunction is an invariable grammatical particle, and it may or may not stand between the items it conjoins." Is this poor grammar ? Interestingly, it did not bring up a violation when I pasted the above sentence into a document, yet it did for one of my own which was similar. — Preceding unsigned comment added by 103.22.211.102 (talk) 10:03, 28 December 2013 (UTC)

History of starting sentences with conjunctions
I can explain the history of ending sentences with prepositions as follows:

Ending sentences with prepositions has always been standard in English. The rule that you can't do so is a rule of Latin grammar; its use in English derives from the impression that English is a Romance language like Latin, not a Germanic language as it really is.

Can anyone give info on the history of starting sentences with conjunctions in a similar way?? Georgia guy (talk) 00:51, 26 January 2015 (UTC)

Extremely Anglocentric Article
As I've stated before, the title of this article is not English Conjunction, but rather simply Conjunction; hence, I suggest we make this article cross-linguistically relevant. As a related side note, this article's text is largely based on traditional grammar, rather than modern linguistics. I think we had best have information on conjunctions and maybe even corresponding structures in other languages; I could help somewhat with Chinese, and more so with Sumerian. Jamutaq (talk) 21:35, 27 February 2015 (UTC)
 * This article does mention some other languages, specifically the West Germanic ones. But it needs some expansion in this area. (Or perhaps, it could be renamed to "Conjunctions in English Grammar", or something similar?) I actually came to this article wondering how English conjunctions compare to conjunctions in other languages. For example, is the confusion between the logical concepts of "exclusive or" and "inclusive or" universal? If not, what languages provide counterexamples? Some research on this topic lead me to believe that classical Latin did have a distinction, with "aut" and "vel" being used, but I'm not certain I understood correctly. Is it known if any language has a unique conjunction for every one of the 16 binary truth functions? Also, apparently classical Arabic required all lists to contain an "and" after each element "I want an apple, an orange, a date, and a plum" would be "I want an apple and an orange and a date and a plum" Just random thoughts on conjunctions across languages, I guess. I hope this might help in expanding this article! JonathanHopeThisIsUnique (talk) 04:23, 12 November 2017 (UTC)

Self-demonstration of starting sentences with conjunctions
The "Starting a sentence" section of the article currently has a couple of sentences that are clearly intended to serve as examples of the subject they're talking about:

While this sort of wink-wink-nudge-nudge "see, look, I'm doing it right now" demonstration might be appropriate on a TV Tropes page, I don't think it's appropriate on Wikipedia. In particular, the sentence beginning with "and" seems clearly shoehorned in for the sake of said demonstration. To be clear, I'm not disagreeing that it's fine English (and otherwise Wikipedia-appropriate) to begin sentences with conjunctions. But if we want to illustrate the concept, we should do so via explicit examples (of which a profusion is already found immediately beneath), not in this unencyclopedic way. 97.103.35.122 (talk) 03:29, 2 March 2015 (UTC)
 * I appreciate someone saying that and being bold enough to change the wording, since I also found it a bit cheesy. I might've tried to change it, but then been reverted. — Eru·tuon 02:16, 4 March 2015 (UTC)
 * I agree. Take note of the lead section, too. I might change it later. CtP  (t • c) 19:49, 3 May 2015 (UTC)

I changed it, as it jars with me too. TrottieTrue (talk) 12:13, 11 November 2020 (UTC)

Examples
Two of the examples of conjunctions used to start a sentence are from Adventures of Huckleberry Finn. But that novel is written from the point of view of Huckleberry Finn himself, who had very limited education and used nonstandard grammar frequently. So those aren't good examples of sentences beginning with conjunctions "in even the most formal writing". --Metropolitan90 (talk) 02:17, 17 September 2015 (UTC)

No semicolon preceding coordinating conjunction?
In the examples given for coordinating conjunctions, semicolons are used to link the two clauses, e.g. "they don't gamble; neither do they smoke". According to the Wikipedia article on semicolons, however, "[semicolons are used] between closely related independent clauses not conjoined with a coordinating conjunction, when the two clauses are balanced, opposed or contradictory" (italics mine).

Does anybody care to comment on this contradiction? Which one is correct? Which should be changed? MrSparkle713 (talk) 14:56, 21 September 2015 (UTC)

if only, than
Is "if only...than" a conjunction? "if only the ground is broken up once a year, than it will in many places with any amount of care."- Wild Apples by Henry David Thoreau117.216.31.248 (talk) 11:57, 1 November 2015 (UTC)

 * Read: .... it will grow faster ... or ... than it will ...". --Boson (talk) 16:22, 1 November 2015 (UTC)

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Reasons that justify a statement as distinct from giving a reason for it
Microsoft® Encarta® 2009 reads as follows

Because and for are both used to introduce reasons that justify a statement as distinct from giving a reason for it: You must have forgotten to invite them, because they didn't turn up. He blushed, for he knew he had been caught out. However, using the same two examples above, I do not know how I would "give a reason for a statement" instead. --Backinstadiums (talk) 16:54, 26 December 2019 (UTC)

Correlative conjunction: where... there; when . . . then; notwithstanding . . . yet
Garner's fourth edition, page 225, mentions ''where... there; when. . . then; notwithstanding. . . yet'' --Backinstadiums (talk) 08:44, 4 August 2020 (UTC)

This makes no sense
Just as many Americans love basketball, so many Canadians love ice hockey.

The word "so" in this sentence is an adverb meaning very. Georgia guy (talk) 18:05, 4 November 2022 (UTC)
 * No, it isn't. Although it would perhaps be better phrased as Just as many Americans love basketball, so do many Canadians love ice hockey. --User:Khajidha (talk) (contributions) 13:24, 10 November 2022 (UTC)

"Conjunction (grammar" listed at Redirects for discussion
The redirect [//en.wikipedia.org/w/index.php?title=Conjunction_(grammar&redirect=no Conjunction (grammar] has been listed at redirects for discussion to determine whether its use and function meets the redirect guidelines. Readers of this page are welcome to comment on this redirect at  until a consensus is reached. Utopes (talk / cont) 01:45, 14 February 2024 (UTC)

title: Talk:Conjunction (grammar)