The proton and electron radiation belts at geosynchronous orbit: Statistics and behavior during high‐speed stream‐driven storms

Abstract

The outer proton radiation belt (OPRB) and outer electron radiation belt (OERB) at geosynchronous orbit are investigated using a reanalysis of the LANL CPA (Charged Particle Analyzer) 8‐satellite 2‐solar cycle energetic particle data set from 1976 to 1995. Statistics of the OPRB and the OERB are calculated, including local time and solar cycle trends. The number density of the OPRB is about 10 times higher than the OERB, but the 1 MeV proton flux is about 1000 times less than the 1 MeV electron flux because the proton energy spectrum is softer than the electron spectrum. Using a collection of 94 high‐speed stream‐driven storms in 1976–1995, the storm time evolutions of the OPRB and OERB are studied via superposed epoch analysis. The evolution of the OERB shows the familiar sequence (1) prestorm decay of density and flux, (2) early‐storm dropout of density and flux, (3) sudden recovery of density, and (4) steady storm time heating to high fluxes. The evolution of the OPRB shows a sudden enhancement of density and flux early in the storm. The absence of a proton dropout when there is an electron dropout is noted. The sudden recovery of the density of the OERB and the sudden density enhancement of the OPRB are both associated with the occurrence of a substorm during the early stage of the storm when the superdense plasma sheet produces a “strong stretching phase” of the storm. These storm time substorms are seen to inject electrons to 1 MeV and protons to beyond 1 MeV into geosynchronous orbit, directly producing a suddenly enhanced radiation belt population.

The Contribution of Compressional Magnetic Pumping to the Energization of the Earth's Outer Electron Radiation Belt During High‐Speed Stream‐Driven Storms

“…At geosynchronous orbit, substorm‐injected electrons have typical kinetic energies of 50 to 300 keV (Birn et al, , ; Cayton et al, ; Denton et al, ; Lezniak et al, ), although under special circumstances electrons with energies of 1 MeV can be injected by substorms (cf. Borovsky et al, ; Ingraham et al, ).…”

“…Compressional magnetic pumping should also act on the proton radiation belt with pitch angle scattering occurring via proton interactions with EMIC waves (Shoji & Omura, ; Søraas et al, ) or with whistler‐mode hiss (Kozyra et al, ; Villalon & Burke, ). Examining the proton radiation belt at geosynchronous orbit during 94 high‐speed stream‐driven storms, Borovsky et al () found that the flux of 1 MeV protons systematically increases in the day prior to the onset of a high‐speed stream‐driven storm. At such times before the storm onset, (1) the solar wind passing the Earth is often sector reversal region plasma that is very inhomogeneous (Borrini et al, ; Gosling et al, ) with strong temporal variations in the solar wind ram pressure, and (2) the plasmapause often extends to beyond geosynchronous orbit owing the refilling of the outer plasmasphere (Borovsky & Steinberg, ; Denton & Borovsky, ).…”

Near‐Earth Solar Wind: Plasma Characteristics From ARTEMIS Measurements

“…In addition to magnetic field amplitude and orientation, the solar wind, a supersonic plasma, is characterized by its dynamic pressure, Mach number, and ion and electron temperatures. These parameters can be combined to calculate different complex coupling functions describing the efficiency of solar wind‐driven magnetosphere dynamics (e.g., Balikhin et al, ; Borovsky et al, , and references therein) or can be used alone to investigate the impact of the solar wind on the magnetosphere (e.g., Sergeev et al, ; Yue et al, , and references therein).…”

Sky-distribution of intensity of synchrotron radio emission of relativistic electrons trapped in Earth’s magnetic field

“…Для потоков электронов с Е >1 МэВ наблюдались максимальные значения J m ≥ 10 7 см -2 с -1 [Савенко и др., 1979]. По данным работы [Borovsky et al, 2016]…”