|Advanced Composition Explorer
|Solar and space exploration spacecraft located at the Sun-Earth L1 point. Was the primary source of real time space weather data until DSCOVR took over in 2016.
|Atmospheric Imaging Assembly
|Instrument on the SDO spacecraft. Provides continuous full-disk observations of the solar chromosphere and corona in seven extreme ultraviolet channels.
|Groups of sunspots indicated with a number. Also known as a sunspot region.
|Big Bear Solar Observatory
|Solar observatory located in the USA that has telescopes and instruments specifically used for studying the activities and phenomena of the Sun.
|Area on the Sun where magnetic field lines arch away from the Sun. This enables the solar wind to escape at a high speed and cause dark holes in the corona as seen on solar images.
|Co-rotating Interaction Region
|Term for the compressed boundary between the fast and slow solar wind in a high speed solar wind stream from persistent coronal holes over multiple solar rotations.
|Coronal mass ejection
|Large cloud of solar plasma released into space due to an event on the Sun.
|Deep Space Climate Observatory
|An earth observation and space weather spacecraft operated by NOAA located at the Sun-Earth L1 point. It is the primary source of real time solar wind and IMF data.
|Disappearing Solar Filament
|The disappearance of a solar filament channel often due to a collapse or eruption.
|Disturbance storm time index
|Indicates the strength of the ring current around Earth caused by solar protons and electrons. A negative Dst value means that Earth's magnetic field is weakened. Values of -50nT and lower are generally considered as geomagnetic storm conditions.
|Extreme ultraviolet Imaging Telescope
|Instrument on the SOHO spacecraft. Provides solar imagery in four different wavelengths.
|Electron, Proton, and Alpha Monitor
|Instrument on the ACE spacecraft. Measures a broad range of energetic particles.
|European Space Agency
|European organization dedicated to the exploration of space.
|Electromagnetic radiation spanning from 124 nanometre down to 10 nanometre in the electromagnetic spectrum.
|Extreme Ultraviolet Variability Experiment
|Instrument package on the SDO spacecraft.
|GFZ German Research Centre for Geoscience is the national research center for Earth Sciences in Germany.
|Geostationary Operational Environmental Satellite
|Series of satellites in a geostationary orbit around Earth.
|Heliospheric Current Sheet
|Boundary where the polarity of the Sun's magnetic field changes from north to south. It's shape can be compared to a ballerina's skirt.
|Term used to describe radio waves with a wavelength between 3 and 30 MHz.
|Helioseismic and Magnetic Imager
|Instrument on the SDO spacecraft.
|High Speed Stream
|Stream of solar wind at a higher than average speed. Often used to define solar wind coming from a coronal hole.
|Interplanetary Magnetic Field
|Solar magnetic field carried by the solar wind among the planets of the Solar System.
|Interface Region Imaging Spectrograph
|NASA solar observation spacecraft.
|Lagrangian point 1
|Point in space between two celestial objects where the gravitational pull from the two objects is equal. Several space weather related satellites orbit the Sun-Earth L1 point.
|Large Angle and Spectrometric Coronagraph
|Instrument on the SOHO spacecraft used to detect and study coronal mass ejections.
|Lockheed Martin Solar and Astrophysics Laboratory
|Part of Lockheed Martin which design, build, and operate solar and astrophysical observing instruments.
|Michelson Doppler Imager
|Instrument on the SOHO spacecraft. It is no longer in use.
|Mauna Loa Solar Observatory
|A solar observatory located on the island of Hawaii in the United States of America.
|National Aeronautics and Space Administration
|American agency responsible for the civilian space program as well as aeronautics and aerospace research.
|National Oceanic and Atmospheric Administration
|American scientific agency. The SWPC Forecast Center is jointly operated by NOAA and the USAF.
|A unit of measurement of the strength of a magnetic field often used in space weather.
|Particle flux unit
|A unit of flux intensity. Number of particles registered per second, per square centimeter and per steradian.
|Plasma Magnetometer Solar Weather Instrument
|Three instruments on the DSCOVR spacecraft which measures the solar wind for space weather predictions.
|PRoject for OnBoard Autonomy 2
|ESA spacecraft that has two scientific instruments to observe the Sun.
|Approximate 11-year period of change in the Sun's activity where the polarity of the Sun's large-scale magnetic field flips.
|Solar Dynamics Observatory
|Solar observation spacecraft operated by NASA in a geosynchronous orbit around Earth.
|A sudden impulse occurs when a coronal mass ejection from the Sun collides with Earth’s magnetosphere. This causes the ring current and the horizontal component of the magnetic field to increase. This increase appears as a sudden spike on terrestrial magnetometers.
|Solar Influences Data Analysis Center
|European space weather services provider based in Belgium.
|Stream Interaction Region
|Term for the compressed boundary between the fast and slow solar wind in a high speed solar wind stream.
|Solar and Heliospheric Observatory
|Solar observation spacecraft at the Sun-Earth L1 point.
|Solar proton event
|Also known as a proton storm. If the intensity of protons having an energy of at least 10 MeV is at least 10 pfu at geosynchronous altitudes, then it is categorized as a SPE.
|Solar Sector Boundary Crossing
|Crossing of the Heliospheric Current Sheet resulting in a change in the orientation of the magnetic field of the solar wind.
|Storm Sudden Commencement
|An abrupt change in the northward (X) component of the geomagnetic field. It marks the beginning of a geomagnetic storm.
|Smoothed Sunspot Number
|Averaged sunspot number over a specific period.
|Solar observation spacecraft operated by NASA in an orbit around the Sun. It orbits slightly faster around the Sun than Earth does.
|Solar observation spacecraft operated by NASA in an orbit around the Sun. It orbits slightly slower around the Sun than Earth does.
|Solar Ultraviolet Imager
|Instrument on the GOES-16 satellite. This instrument observes the Sun in six different wavelengths in extreme ultraviolet.
|Space Weather Prediction Center
|Service center that continually monitors and forecasts Earth's space environment. It is the official source of space weather alerts and warnings for the United States.
|United States Air Force
|Service branch of the United States Armed Forces. The SWPC Forecast Center is jointly operated by NOAA and the USAF.
|Coordinated Universal Time
|Primary time standard by which the world regulates clocks and time.
|Very High Frequency
|Term used to describe radio waves with a wavelength between 30 and 300 MHz.
|Very Low Frequency
|Term used to describe radio waves with a wavelength between 3 and 30 kHz.
|Solar X-ray Sensor
|Instrument on the GOES satellites used to measure X-ray output of the Sun.
|Commonly used unit of length for wavelengths of electromagnetic radiation. 1 Ångström equals 10-10 metres, 0.1 nanometres or 100 picometres.