A 30‐Year Simulation of the Outer Electron Radiation Belt. Issue 10 (9th October 2018)

• Record Type: Journal Article
• Authors: Glauert, S. A.; Horne, R. B.; Meredith, N. P.
• Is Part Of: Space weather. Volume 16:Issue 10(2018)
• Page Start: 1498
• Page End: 1522
• Publication Date: 2018-10-09
• Subjects: radiation belt -- long‐term simulation -- high‐energy electrons -- solar cycle; Space environment -- Periodicals; 551.509992
• DOI: 10.1029/2018SW001981
• Languages: English
• ISSNs: 1542-7390

Abstract

Abstract: As society becomes more reliant on satellite technology, it is becoming increasingly important to understand the radiation environment throughout the Van Allen radiation belts. Historically most satellites have operated in low Earth orbit or geostationary orbit (GEO), but there are now over 100 satellites in medium Earth orbit (MEO). Additionally, satellites using electric orbit raising to reach GEO may spend hundreds of days on orbits that pass through the heart of the radiation belts. There is little long‐term data on the high‐energy electron flux, responsible for internal charging in satellites, available for MEO. Here we simulate the electron flux between the outer edge of the inner belt and GEO for 30 years. We present a method that converts the >2‐MeV flux measured at GEO by the Geostationary Operational Environmental Satellites spacecraft into a differential flux spectrum to provide an outer boundary condition. The resulting simulation is validated using independent measurements made by the Galileo In‐Orbit Validation Element‐B spacecraft; correlation coefficients are in the range 0.72 to 0.88, and skill scores are between 0.6 and 0.8 for a range of L ∗ and energies. The results show a clear solar cycle variation and filling of the slot region during active conditions and that the worst case spectrum overlaps that derived independently for the limiting extreme event. The simulation provides a resource that can be used by satellite designers to understand the MEO environment, by space insurers to help resolve the cause of anomalies and by satellite operators to plan for the environmental extremes. Plain Language Summary: Society is becoming more reliant on satellites for navigation, defense, communications, and Earth observation. Increasing numbers of satellites orbit through the Van Allen radiation belts, where charged particles are trapped in orbit around the Earth by the Earth's magnetic field. These radiation belts are very dynamic; the number of electrons, and their energies, can change dramatically in hours in response to changes in the solar wind flowing from the Sun. Since these electrons can damage satellites, it is important to understand the environment that satellites are likely to encounter. Only limited measurements are available throughout the radiation belts, so we have used a physics‐based model to simulate their behavior for 30 years. There is good agreement between our simulation and independent measurements. Our results show significant variations in the radiation belts during the 11‐year solar cycle and that the region between the inner and outer radiation belts, where the electron population is normally low, can become filled during active geomagnetic conditions. The simulation provides a resource that can be used by satellite designers to understand the radiation belt environment, by space insurers to help resolve the cause of malfunctions, and by satellite operators to plan for the environmental extremes. Key Points: A 30-year reconstruction of the outer electron belt is described Results are validated using an independent data set This provides valuable resource for satellite designers, operators, and insurers