| Term (alphabetical) | Definition | Details |
| ACE | Solar satellite | The NASA Advanced Composition Explorer (ACE) satellite enables SWPC to give advance warning of geomagnetic storms. |
| Astronomical Unit | Distance measurement | Defined as the distance between the Sun and the Earth or 149,597,870,700 metres (93 million miles). |
| Atlas-1 | Solar satellite | Launched in 1992 ATLAS-1 was the first in a series of long-range studies by NASA that measured changes in the atmosphere and the sun. |
| Aurora Australis | Charged particle display near the south pole | Charged particles hitting the earth’s magnetosphere in the southern hemisphere cause a slowly flickering curtain of colour in the sky. The higher the speed and number of charged particles, the brighter the aurora and the further north it can be seen from the south pole. |
| Aurora Borealis | Charged particle display near the north pole | Charged particles hitting the earth’s magnetosphere in the northern hemisphere cause a slowly flickering curtain of colour in the sky. The higher the speed and number of charged particles, the brighter the aurora and the further south it can be seen from the north pole. The Carrington event of 1859 caused aurorae in the US that were so bright that their glow awoke gold miners, who began preparing breakfast because they thought it was morning. For around four days people in the northeast United States could even read a newspaper by the aurora’s light. |
| BGS | British Geological Society (UK) | Founded in 1835, the BGS is a world-leading geoscience centre for survey and monitoring, modelling and research, and data and knowledge. |
| CAA | Civil Aviation Authority (UK) | The Civil Aviation Authority (CAA) is the statutory corporation which oversees and regulates all aspects of civil aviation in the United Kingdom, including aspects of space weather. As of 2014 the new Directorate of Aviation Security within the CAA manages rule-making and compliance to deliver proportionate and focussed regulation for UK aviation to ensure the highest standards of security across the civil aviation sector. The CAA also manages all national security vetting for the aviation industry. |
| Carrington event 1859 | The largest solar flare and CME on record | Richard Christopher Carrington (1826–1875) was a British scientist and the first person to study solar flares on the Sun as localised visible brightening of small areas within a sunspot group. From August 28 to September 2 1859 numerous sunspots were observed on the Sun. On September 1st 1859 Carrington observed an intense flare on the sun that lasted around five minutes, which was independently observed by Richard Hodgson (1804–1872), and subsequently called the Carrington Event. The solar flare he saw was accompanied by a massive coronal mass ejection (CME) comprising of clouds of electrons, ions, and atoms dr4iven through the corona of the sun into space. This cloud reached the Earth 17.6 hours later, causing telegraph wires to spark and giving operators electric shocks. It is still regarded as the largest CME in modern times. |
| Carrington rotation | Period of rotation of the sun | Named after Richard Christopher Carrington. The Carrington rotation is a system for comparing locations on the Sun over a period of time, allowing the following of sunspot groups or reappearance of eruptions at a later time. As solar rotation is variable with latitude, depth and time, any such system is necessarily arbitrary and only makes comparison meaningful over moderate periods of time. Solar rotation is arbitrarily taken to be 27.2753 days for the purpose of Carrington rotations. Each rotation of the Sun under this scheme is given a unique number called the Carrington Rotation Number, starting from November 9th 1853. |
| Carrington super flare | Solar flare and coronal mass ejection Sept 1859 | Solar flare associated with a major coronal mass ejection (CME) that travelled directly toward Earth, taking 17.6 hours to make the 150 million kilometre (93 million mile) journey. It is believed that the relatively high speed of this CME (typical CMEs take several days to arrive at Earth) was made possible by a prior CME, perhaps the cause of the large aurora event on August 29, that “cleared the way” of ambient solar wind plasma for the Carrington Event. |
| CME | Coronal Mass Ejection | A massive burst of gas and magnetic field arising from the solar corona and being released into the solar wind sometimes referred to as a Solar EMP. |
| COBRA | Cabinet Office Briefing Room A (UK) | COBR is a suite of secure, hardened meeting rooms in the Cabinet Office Briefing Rooms at 70 Whitehall, used for different committees which co-ordinate the actions of bodies within the Government of the UK or by various UK government departments in response to instances of national or regional crisis, or during events abroad with major likely impact on the UK. COBRA (Cabinet Office Briefing Room A) is or COBR is now a term used to refer to both the facility and the committee. |
| DC induction | Direct Current induction | Solar flares can create large DC currents to be induced in any long lengths of a metal conductor, particularly power transmission lines. Since both ends of a power transmission line are terminated by a transformer, the DC current will induce a DC magnetization in the transformer cores. Since transformers are run close to the saturation magnetization of the core, the DC shift in magnetization will start saturating the transformer during part of the AC (alternating current) cycle, leading to a strong increase in current, which produces large I2R losses. In effect it’s not the deposited flare energy that destroys these transformers and/or triggers the overload circuits, but the fact that they start acting like magnetic amplifiers, drawing a large multiple of the flare energy from the power plants. solution to this (rare) problem lies in better protection circuits for power networks, more robust transformer design, the addition of DC blocking circuits and, ultimately, in decentralized power production. |
| DoT | Department of Transport (UK) | UK government department that plans and invests in transport infrastructure, to support the transport network for UK businesses and to enable people and goods to travel around the UK. |
| E1 EMP | Nuclear Electromagnetic Pulse | E1 is a very brief but intense electromagnetic field that induces very high voltages in electrical conductors. E1 causes most of its damage by causing electrical breakdown voltages to be exceeded. E1 can destroy computers and communications equipment and it changes too quickly (nanoseconds) for ordinary surge protectors to provide effective protection against it. |
| E2 EMP | Lightning or nuclear Electromagnetic Pulse | E2 is scattered gamma rays and inelastic gammas produced by lightning or by neutrons from a nuclear explosion. The frequency of lightning around the world means there are many existing protective measures against occasional lightning strikes for critical infrastructure systems. In nuclear devices the E2 component is an intermediate time pulse that, by the IEC definition, lasts from about 1 microsecond to 1 second after the explosion. |
| E3 EMP | Solar Electromagnectic Pulse | The E3 component caused by a solar flare can create a geomagnetic storm, producing temporary distortion of the Earth’s magnetic field. E3 can produce geomagnetically induced currents in long electrical conductors, damaging components such as power lines and power transformers. E3 can also be caused by the very slow pulse from a nuclear explosion and lasting tens to hundreds of seconds. |
| EirGrid | Ireland’s transmission grid company | EirGrid Group is a state-owned company that manages and operates the transmission grid across the island of Ireland. This includes the high-voltage network that brings power from generators and supplies wholesale energy to industrial users. The EirGrid also supplies the electricity distribution network. |
| Electromagnetic forming | EMP used in manufacturing | The large forces generated by electromagnetic pulses can be used to shape or form objects as part of their manufacturing process. |
| Electromagnetic interference | Interference from an EMP | Many common man-made devices create electrical interference and small EMPs including the switching action of electrical or digital electronic circuitry (whether isolated or repetitive as a pulse train). Electric motors can create a train of pulses as the internal electrical contacts make and break connections as the armature rotates. Petrol / gasoline engine ignition systems can create a train of pulses as the spark plugs are energised or fired. Power line surges can be up to several kilovolts, enough to damage electronic equipment conected to mains electricity that is insufficiently protected. |
| EMP | Electromagnetic Pulse | An EMP arises where the source emits a short-duration pulse of energy. The energy is usually broadband by nature, although it often excites a relatively narrow-band damped sine wave response in the victim. Some types are generated as repetitive and regular pulse trains. Different types of EMP arise from natural, man-made and weapons effects. |
| EMP simulator | Electromagnetic Pulse simulator | To test the effects of EMP on engineered systems and equipment, an EMP simulator may be used. US devices include HAGII-C and EMPRESS 1, which has a large shoreline antenna. Nearly all of these large EMP simulators used a specialized version of a Marx generator. |
| Empress 1 | Large EMP simulator facility | Electro Magnetic Pulse Radiation Environmental Simulator for Ships I (EMPRESS I). EMPRESS 1 has a large shoreline antenna to test the effects of EMP on engineered systems and equipment, including large fleet battleships. |
| EPA | Environment Protection Agancy (US) | The United States Environmental Protection Agency (EPA or U.S. EPA) is an agency of the federal government of the United States which was createdin 1970 for the purpose of protecting human health and the environment by writing and enforcing regulations based on laws passed by Congress. |
| EPRI | Electric Power Research Institute (US) | The EPRI conducts research on issues related to the electric power industry. It is a non-profit organization funded by the electric utility industry, founded in 1972 and headquartered in Palo Alto, California. EPRI is primarily a US-based organization, but receives international participation. EPRI’s research covers different aspects of electric power generation, delivery and its use. |
| ESA | European Space Agency | intergovernmental organisation of 22 member states dedicated to the exploration of space. Established in 1975 and headquartered in Paris, France, ESA has a worldwide staff of about 2,000 and an annual budget of about €5.25 billion / US$5.77 billion (2016). |
| ESD | Electrostatic Discharge | ESD events are characterised by high voltages of many kV but small currents and sometimes cause visible sparks. ESD is treated as a small, localised phenomenon, although technically a lightning flash is a very large ESD event. |
| Explosively pumped flux compression generator | NNEMP device | Non-nuclear electromagnetic pulse (NNEMP) device generating an electromagnetic pulse without use of nuclear technology. The concept of the explosively pumped flux compression generator for generating a non-nuclear electromagnetic pulse was conceived as early as 1951 by Andrei Sakharov. |
| Faraday cage | Cage to protect against electromagentic fields | A Faraday cage or Faraday shield is an enclosure designed to block electromagnetic fields. A Faraday shield may be formed by a continuous covering of conductive material or, in the case of a Faraday cage, by a mesh of such materials. A home microwave oven can be used as a Faraday cage when it is not switched on. |
| Gamma ray | Type of high energy electromagnetic radiation | Gamma rays are penetrating electromagnetic radiation arising from the radioactive decay of atomic nuclei, and are biologically hazardous. Natural sources of gamma rays on Earth are observed in the gamma decay of radionuclides and secondary radiation from atmospheric interactions with cosmic ray particles. There are rare terrestrial natural sources, such as lightning strikes and terrestrial gamma-ray flashes. Gamma rays are also produced by nuclear fusion in the sun, but are absorbed or inelastically scattered by the stellar material in the sun, reducing their energy before escaping and are not observable from Earth as gamma rays. Gamma rays typically have energies above 100 keV and have frequencies above 10 exahertz (or >1019 Hz) and wavelengths less than 10 picometers (10−11 m), less than the diameter of an atom. |
| Geomagnetic storm | Storm created by a solar flare | One of the largest recorded geomagnetic storms (as recorded by ground-based magnetometers) occurred in September 1859 (the Carrington Event). Aurorae were seen around the world, in the northern hemisphere as far south as the Caribbean and visible as far from the poles as Sub-Saharan Africa (Senegal, Mauritania, perhaps Monrovia, Liberia), Monterrey and Tampico in Mexico, Queensland, Cuba and Hawaii. |
| GIC | Geomagnetically Induced Current | Geomagnetically induced currents (GIC), affecting the normal operation of long electrical conductor systems and are a manifestation at ground level of space weather. GIC have been regularly measured in Canadian, Finnish and Scandinavian power grids and pipelines since the 1970s. GIC of tens to hundreds of amperes have been recorded. During space weather events, electric currents in the magnetosphere and ionosphere experience large variations, which manifest also in the Earth’s magnetic field. These variations induce currents (GIC) in conductors operated on the surface of Earth. Electric transmission grids and buried pipelines are common examples of such conductor systems. GIC can cause problems, such as increased corrosion of pipeline steel and damage to high-voltage power transformers. |
| GNSS | Global Navigation Satellite System | GNSS is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage. This term includes e.g. the GPS, GLONASS, Galileo, Beidou and other regional systems. |
| GOES | Solar satellite | The GOES 12 through 15 spacecraft each carry a sophisticated X-ray telescope called the Solar X-ray Imager (SXI) to monitor the Sun’s hot outer atmosphere, or corona. |
| GPS | Global Positioning System | The Global Positioning System, originally Navstar GPS, is a space-based radio navigation system owned by the United States government and operated by the United States Air Force. |
| H-Alpha classification | Solar flare classification system | An earlier flare classification is based on H-Alpha (Hα) spectral observations. The scheme uses both the intensity and emitting surface. The classification in intensity is qualitative, referring to the flares as: (f)aint, (n)ormal or (b)rilliant. |
| Heliophysics | The study of the sun and its physical effects | Heliophysics is the study of the effects of the sun on the solar system; it addresses problems that span a number of existing disciplines – solar and heliospheric physics, and magnetospheric and ionospheric physics for the Earth and other planets. |
| HINODE | Solar satellite | Hinode is a joint Japan/US/UK mission (formerly known as Solar-B) led by the Japanese Aerospace Exploration Agency’s (JAXA) Space Science Research Division (formerly the Institute of Space and Astronautical Science or ISAS). It is designed to explore the magnetic fields in the solar corona and to improve our understanding of the mechanisms that power the solar atmosphere and drive solar eruptions. |
| Ionosphere | Region of the earth’s atmosphere 60km to 1,000km | The ionosphere is critical to long-range radio communications around the globe. X-rays and UV radiation emitted by solar flares can affect Earth’s ionosphere and disrupt long-range radio communications. Direct radio emission at decimetric wavelengths may disturb the operation of radars and other devices that use those frequencies. |
| JRC | Joint Research Centre (Europe) | The Joint Research Centre is the European Commission’s science and knowledge service which employs scientists to carry out research in order to provide independent scientific advice and support to EU policy. |
| KeV | Kilo electron Volts | 1 KeV is the unit of energy equal to approximately 1.6×10−16 joules (J). By definition 1eV is the amount of energy gained or lost by the charge of a single electron moving across an electric potential difference of one volt. |
| Kill pulse | High intensity EMP | Pulse that destroys equipment, systems, services, satellites or infrastructure such as power lines |
| KV/m | KiloVolts per metre | Unit of electronic charge over a given area |
| Lagrange point | Stable gravitational point in space | Lagrange points are positions in an orbital configuration of two large bodies where a small object affected only by gravity can maintain a stable position relative to the two large bodies. The Lagrange points mark positions where the combined gravitational pull of the two large masses provides precisely the centripetal force required to orbit with them. There are five such points, L1 to L5, all in the orbital plane of the two large bodies. The first three are on the line connecting the two large bodies; the last two, L4 and L5, each form an equilateral triangle with the two large bodies. The two latter points are stable, which implies that objects can orbit around them in a rotating coordinate system tied to the two large bodies. |
| LEMP | Lightning Electromagnetic Pulse | Scattered gamma rays and inelastic gammas produced by neutrons after lightning. Critical infrastructure systems have existing protective measures for defence against occasional lightning strikes. |
| Light Year | How far light travels in a year | 9.46 trillion kilometres, used as a measure of distance in astronomy. |
| Lightning | High energy EMP type 2 created during storms | Electromagnetic pulses are generated by lightning (LEMP). The discharge is typically an initial huge current flow of many thousands of amps, followed by a train of pulses of decreasing energy. |
| Magnetic reconnection | Solar flare phenomenon | Scientific research suggests that the phenomenon of magnetic reconnection leads to the copious acceleration of charged particles, mainly electrons, interact with the plasma medium in the sun. This phenomenon causes solar flares. |
| Magnetometer | Insrument to measure magnetism | Measures magnetism including the magnetisation of a magnetic material like a ferromagnet, or the direction, strength, or relative change of a magnetic field at a particular location. A compass is a simple type of magnetometer, one that measures the direction of an ambient magnetic field. |
| Met office | Meteorological Office (UK) | The United Kingdom’s national weather service. It is an executive agency and trading fund of the Department for Business, Energy and Industrial Strategy (BIS). The Met Office makes meteorological predictions across all timescales from weather forecasts to climate change. |
| Meteoric EMP | Electromagnetic Pulse created by a meteor | The discharge of electromagnetic energy resulting from either the impact of a meteoroid with a spacecraft or the explosive breakup of a meteoroid passing through the Earth’s atmosphere. |
| MeV | Mega electron Volts | 1 MeV is the unit of energy equal to approximately 1.6×10−13 joules (J). By definition 1 eV is the amount of energy gained or lost by the charge of a single electron moving across an electric potential difference of one volt. |
| MOSWOC | Met Office Space Weather Operations Centre (UK) | Set up in 2014 and part of the UK Met Office. MOSWOC provides forecasts that enable authorities and organisations to prepare for and respond to the risk of space weather impacts. |
| nanoTesla / min | Unit of magnetic field | The nanotesla (nT), where one nanotesla equals 10−9 tesla, is used to measure electric field intensity. A nanotesla is equivalent to one gamma, a unit originally defined as 10−5 gauss, which is the unit of magnetic field in the centimetre-gram-second system. Both the gauss and the gamma are still frequently used. |
| NASA | National Aeronautics and Space Administration (US) | The National Aeronautics and Space Administration is an independent agency of the executive branch of the United States federal government responsible for the civilian space program, as well as aeronautics and aerospace research. |
| National Grid Plc | UK and US electric and gas utility company | National Grid plc. is a British multinational electricity and gas utility company headquartered in Warwick, United Kingdom. Its principal activities are in the United Kingdom and North-eastern United States. National Grid has a primary listing on the London Stock Exchange, and is a constituent of the FTSE 100 Index. It had a market capitalisation of approximately £40.4 billion on 23 September 2016, the twentieth largest of any company |
| NATS | National Air Traffic Services (UK) | NATS holdings, formerly National Air Traffic Services and commonly referred to as NATS, is the main Air Navigation Service Provider in the United Kingdom. They control flights and monitor hazards to all commercial aircraft in UK airspace and to from UK destinations. |
| NOAA | National Oceanic and Atmosphere Administration (US) | The National Oceanic and Atmospheric Administration is an American scientific agency within the United States Department of Commerce that focuses on the conditions of the oceans and the atmosphere. |
| NSRA | National Security Risk Assessment (UK) | The National Security Risk Assessment 2015 covers the threats faced by the UK inh the National Risk Register (NRR), including its Overseas Territories and overseas interests. |
| NSSP | National Space Security Policy (UK) | Sets out a coherent approach to the UK’s space security interests and outlines measures to make the United Kingdom more resilient to the risk of disruption to space services and capabilities, enhance national security interests through space and to promote a safe and more secure space environment. |
| Nuclear fusion | Type of nuclear reaction | Reaction in which two or more atomic nuclei come close enough to form one or more different atomic nuclei and subatomic particles (neutrons or protons). |
| Parker Solar Probe | Solar satellite | Launched August 2018 and operational from end 2018, it will study what drives the solar winds that buffet the Earth. It will spend the next seven years making 24 loops around the Sun to study its atmosphere, using Venus to slingshot it back into orbit. |
| Quebec geomagnetic storm 1989 | Geomagnetic storm affecting Quebec electricity system | A severe geomagnetic storm struck Earth on March 13 1989. It caused a nine-hour outage of Hydro-Québec’s electricity transmission system. The geomagnetic storm causing this event was itself the result of a coronal mass ejection on March 9 1989, a delay of around 3 days from sun to earth. On March 6th a very large X15-class solar flare also occurred. 3.5 days later at 2:44 am EST on March 13, a severe geomagnetic storm struck Earth. The variations in the earth’s magnetic field tripped circuit breakers on Hydro-Québec’s power grid. The utility’s very long transmission lines and the fact that most of Quebec sits on a large rock shield prevented current flowing through the earth, finding a less resistant path along the 735 kV power lines. The Canadian James Bay network went offline in less than 90 seconds, giving Quebec its second massive blackout in 11 months. In August 1989, another storm caused a halt of all trading on Toronto’s stock market. |
| RAE | Royal Academy of Engineering (UK) | The UK’s national academy for engineering, bringing together engineering expertise to advance and promote excellence in engineering. Authors of the 2013 70 page report: Extreme Space Weather: impacts on engineered systems and infrastructure. |
| RAS | Royal Astronomical Society (UK) | The Royal Astronomical Society, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. |
| RHESSI | Solar satellite | Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) is a NASA Small Explorer (SMEX) launched on 5 February 2002 to study solar flares through X-ray and gamma-ray imaging spectroscopy observations. RHESSI’s primary mission is to explore the basic physics of particle acceleration and explosive energy release in solar flares. |
| Richard Christopher Carrington | British solar scientist | Richard Christopher Carrington (1826–1875) was a British scientist and the first person to study solar flares on the Sun as localised visible brightening of small areas within a sunspot group. On September 1st 1859 he observed an intense flare on the sun that lasted around five minutes, which was subsequently called the Carrington Event. |
| SDO | Solar satellite | Launched on February 11 2010, the Solar Dynamics Observatory is the first mission in NASA’s Living With a Star (LWS) Program, a program designed to understand the causes of solar variability and its impacts on Earth. SDO is designed to help understand the Sun’s influence on Earth and Near-Earth space by studying the solar atmosphere on small scales of space and time and in many wavelengths simultaneously. |
| SEIEG | Space environment impacts expert group (UK) | Part of UK National Risk Assessment. Space weather discussions started May 2010 and the Space Environment Impacts Expert Group was formed Nov 2010. SEIEG provides independent scientific advice with an emphasis on peer reviewed scientific evidence. Space weather risk was formally recognised in the UK in publication of The National Risk Register NRR in Jan 2012. |
| Severe space weather risk | Risks due to varying conditions in the solar system | Conditions causing sever risk to the space surrounding the Earth, including conditions in the magnetosphere, ionosphere, thermosphere, and exosphere. |
| Sigmoid | S shaped plasma in the solar corona | Solar scientists in America noted that an S shape in the solar corona is a good indication that an eruption and CME is about to occur. These S shapes are called sigmoids and are magnetic flux ropes with a left or right-handed twist. |
| SOHO | Solar and Heliospheric Observatory – solar satellite | SOHO was launched in 1995 and is designed to study the internal structure of the sun, its extensive outer atmosphere and the origin of the solar wind. |
| Solar-C | Solar satellite | Solar-C is the next Japanese solar mission following Yohkoh (Solar-A) and Hinode (Solar-B). Scheduled for launch in Feb 2019 it will study the magnetic structure inside the Sun to determine its role in the heating and dynamics of the solar atmosphere. |
| Solar arcade | Magnetic loops of force on the sun | A series of closely occurring loops of magnetic lines of force that occur on the sun. These lines of force quickly reconnect into a low arcade of loops |
| Solar atmosphere | Atmosphere of the sun | The sun has several layers in its solar atmosphere, including the photosphere, chromosphere, and corona. The corona is created when the plasma medium is heated to tens of millions of degrees Centigrade |
| Solar cycle | 11 year change in the sun’s activity | The solar cycle or solar magnetic activity cycle is the nearly periodic 11-year change in the Sun’s activity. Rudolf Wolf’s numbering scheme, the 1755–1766 cycle is traditionally numbered 1. Solar cycles include changes in the levels of solar radiation and ejection of solar material and appearance, such as changes in the number and size of sunspots, flares, and other manifestations. The changes on the Sun cause effects in space, in the atmosphere, and on the Earth’s surface. |
| Solar EMP | Electromagnetic Pulse generated by the sun | A massive burst of gas and magnetic field arising from the solar corona and being released into the solar wind. Due to the similarity between solar-induced geomagnetic storms and nuclear E3, it is common to refer to solar-induced geomagnetic storms as Solar EMP. However Solar EMP does not include an E1 or E2 component. |
| Solar flare | High energy emission from the sun’s surface | A sudden flash of brightness observed near the Sun’s surface involving a very broad spectrum of emissions, first observed by Galileo. A solar flare requires an energy release of up to 6 × 1025 joules of energy (roughly the equivalent of 160,000,000,000 megatons of TNT, or over 25,000 times more energy than released from the impact of Comet Shoemaker–Levy 9 with Jupiter). Flares are often, but not always, accompanied by a spectacular coronal mass ejection. The flare ejects clouds of electrons, ions, and atoms through the corona of the sun into space. These clouds typically reach Earth 12 hours to 3 days after the event. |
| Solar Orbiter | Solar satellite | By approaching as close as 48 solar radii (RSun), the Solar Orbiter will view the solar atmosphere with unprecedented spatial resolution. Over extended periods the Solar Orbiter will deliver images and data of the polar regions and the side of the Sun not visible from Earth. |
| Solar Probe + | Solar satellite | Solar Probe Plus will be a unique mission, exploring what is arguably the last region of the solar system to be visited by a spacecraft, the Sun’s outer atmosphere or corona. |
| Solar superstorm (solar ‘pulse’) | Very large solar flare | Solar flares eject clouds of electrons, ions, and atoms through the corona of the sun into space. These ‘pulses’ typically reach Earth 12 hours to 3 days after the event. |
| Solar wind | Charged particles from the sun’s corona | The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma consists of mostly electrons, protons and alpha particles with thermal energies between 1.5 and 10 keV. Embedded within the solar-wind plasma is the interplanetary magnetic field. The solar wind varies in density, temperature and speed over time and over solar latitude and longitude. Its particles can escape the Sun’s gravity because of their high energy resulting from the high temperature of the corona, which in turn is a result of the coronal magnetic field. |
| SOLRAD | Solar satellite | Series of satellites of the SOLRAD (Solar Radiation) program that began in 1960 to provide continuous coverage of solar radiation with a set of standard photometers. |
| Space weather | Varying conditions in the solar system | Space weather is a branch of space physics and aeronomy concerned with the time varying conditions within the Solar System, including the solar wind, emphasising the space surrounding the Earth, including conditions in the magnetosphere, ionosphere, thermosphere, and exosphere. Different aspects of space weather have a variety of impacts on mankind and the technology we use. |
| Space weather scales | MOSWOC and NOAA scales | MOSWOC uses the numbered scales developed by NOAA that are similar to those used to describe hurricanes or earthquakes, with a UK-specific impact scale to use in forecasts, alerts and warnings based on the 2013 RAE report on the impacts of extreme space weather on UK engineered systems and infrastructures. These scales include impacts on radio blackouts (R scale), geomagnetic storms (G scale) and solar radiation storms (S scale). |
| Space Weather Preparedness Strategy | Report from BIS in 2015 (UK) | Report on the causes and likely effects of a large solar flare, coronal mass ejection (CME) and geomagnetic storm and how to plan for and mitigate its effects on the UK’s infrastructure including transport, utilities and local populations. |
| STEREO | Solar Terrestrial Relations Observatory | Solar observation mission. Two space-based observatories launched in 2006 – one ahead of Earth in its orbit, the other trailing behind. With this new pair of viewpoints, scientists will be able to see the structure and evolution of solar storms as they blast from the Sun and move out through space. |
| Sunspot | Brighter regions of the sun’s surface | Sunspots are hotter regions of the sun in the corona part of its atmosphere or photosphere. The sunspot colour is created by plasma at tens of millions of degrees Centigrade. |
| SWPC | Space Weather Prediction Center (US) | Laboratory and service center of the US National Weather Service (part of the National Oceanic and Atmospheric Administration (NOAA) located in Boulder, Colorado. SWPC continually monitors and forecasts Earth’s space environment, providing solar-terrestrial information. SWPC is the official source of space weather alerts and warnings for the United States. |
| Tesla | Unit of magnetic flux density | The tesla (T) is a derived unit of magnetic flux density (informally, magnetic field strength) in the International System of Units. One tesla is equal to one weber per square metre. The unit was announced during the General Conference on Weights and Measures in 1960 and is named in honour of Nikola Tesla. |
| TRACE | Solar satellite | Transition Region And Coronal Explorer (TRACE) is designed to make quantitative observations showing the connections between fine-scale magnetic fields and the associated plasma structures in the solar atmosphere. |
| UK Space Agency | Body responsible for the UK space program | Executive agency of the Government of the United Kingdom, responsible for the United Kingdom’s civil space programme. It was established on 1 April 2010 to replace the British National Space Centre (BNSC) and took over responsibility for government policy and key budgets for space exploration, and represents the United Kingdom in all negotiations on space matters. |
| Van de graaff generator | Generator to create an Electromagnetic Pulse | These generators create a large, fast electrostatic discharge (see ESD) |
| X-class flare | Type of high energy solar flare | The classification system for solar flares uses the letters A, B, C, M or X, according to the peak flux in watts per square metre (W/m2) of X-rays with wavelengths 100 to 800 picometers, as measured at the Earth’s orbital distance by the GOES spacecraft. |