The electron flux measured by the GOES satellites indicates the intensity of the outer electron radiation belt at geostationary orbit. Measurements are made in ten differential flux channels and one integral flux channel. The differential flux channels measure electrons in ten discrete bands from 50 thousand electron volt (keV) to 4 million electron volts (MeV). The integral channel measures all electrons with energies greater than 2 MeV.
Electron Event ALERTS are issued when the >2 MeV electron flux exceeds 1000 particles/(cm2 s sr). High fluxes of energetic electrons are associated with a type of spacecraft charging referred to as internal charging. Internal charging occurs when energetic electrons penetrate into spacecraft components and result in a buildup of charge within the material. When the accumulated charge becomes sufficiently high, a discharge or arching can occur. This discharge can cause anomalous behavior in spacecraft systems and can result in temporary or permanent loss of functionality.
SWPC provides 5-minute averages of differential electron flux (electrons/(cm² s sr keV)) in ten discrete channels from 50 keV to 4 MeV, and 5-minute averages of integral electron flux (electrons/(cm² s sr KeV)) with energies greater than 2 MeV. The radiation belt electron fluxes vary dramatically over time scales ranging from minutes to years. Abrupt increases and decreases in flux can occur due to reconfigurations in the magnetospheric magnetic field, as well as due to various particle acceleration and loss mechanisms.
When measured at geostationary orbit, the electron fluxes also exhibit a substantial spatial variability, independent of the temporal changes due to magnetic field reconfiguration and particle acceleration/loss. The electron fluxes at geostationary orbit typically have their highest values near local noon and their lowest values near local midnight. This spatial feature is due to the structure of the magnetospheric magnetic field, strong at noon and weak at midnight, caused by the pressure of the solar wind on the day side of the magnetosphere.
Note: The >2 MeV electron channel may be contaminated by solar energetic protons. Starting with GOES-16, this effect is due to protons above several hundred MeV and is weaker than it was on earlier GOES satellites. However, as of December 2024, this effect has not been quantified during a large S3 or S4 solar proton event.
GOES electron measurements have been made since the first GOES satellite was launched in 1975, and prior to that they were made on the NASA Synchronous Meteorological Satellites (SMS 1 and 2). SMS were the forerunners to the GOES operational system.
The dynamic plot above can be downloaded in multiple image formats using the menu at the upper right. The menu also offers the ability to download the displayed numerical data in JSON format.
Numerical data are also available directly from SWPC's data service at:
https://services.swpc.noaa.gov/json/goes/
In that directory the file instrument-sources.json provides the mapping of primary and secondary measurements from each instrument to the satellite from which that measurement is made. The file satellite-longitudes.json provides the longitudes of the satellites. Observation data are found under the primary and secondary subdirectories.
NOTE: After January 31, 2020 other JSON/GOES data files and subdirectories will be removed. This is due to discontinuation of GOES-14 and GOES-15 observations on that date.
Data, plots, and documentation for non-real time GOES charged particle data are available from the NOAA National Centers for Environmental Information (NCEI). Both operational and science-quality reprocessed Space Environment In Situ Suite (SEISS) particle data from the GOES-R series (GOES-16 through -19) are available at https://www.ncei.noaa.gov/products/goes-r-space-environment-in-situ. Science-quality and operational charged particle data, plots and documentation for GOES-1 through -15 are available at https://www.ncei.noaa.gov/products/goes-1-15/space-weather-instruments.