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 that could be 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,Paul Dickson, Sputnik: The Launch of the Space Race. (Toronto, Canada: MacFarlane Walter & Ross, 2001), p. 190. 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.Cauffman, D., and D. Gurnett (1971), Double-Probe Measurements of Convection Electric Fields with the Injun-5 Satellite, J. Geophys. Res., 76(25), pp. 6014–6027. In the early 1970s, Triad data demonstrated that permanent electric currents flowed between the auroral oval and the magnetosphere.A. J. Zmuda and J. C. Armstrong, The Diurnal Flow Pattern of Field-Aligned Currents, Journal of Geophys. Res., 79, 31, 4611 pp., 1974.
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.
Programs 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.NOAA/NWS Space Weather Prediction Center – Homepage.
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.
ICAO Space Weather Advisory The International Civil Aviation Organization (ICAO) implemented a Space Weather Advisory program in late 2019. Under this program, ICAO designated four global space weather service providers: The United States, which is done by the National Oceanic and Atmospheric Administration (NOAA) Space Weather Prediction Center. The Australia, Canada, France, and Japan (ACFJ) consortium, comprising space weather agencies from Australia, Canada, France, and Japan. The Pan-European Consortium for Aviation Space Weather User Services (PECASUS), comprising space weather agencies from Finland (lead), Belgium, the United Kingdom, Poland, Germany, Netherlands, Italy, Austria, and Cyprus. The China-Russian Federation Consortium (CRC) comprising space weather agencies from China and the Russian Federation.
Government risk assessments Space weather is listed as a natural hazard on risk assessments in countries such as: Ireland The United Kingdom New Zealand
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.
Effects 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, as well as accelerate satellite re-entries from LEO. The geomagnetic storm adds heat to the thermosphere, causing the thermosphere to expand and rise, further 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.
Ground systems 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