Observations of magnetospheric bursts of high-energy protons and electrons at approx. 35 R/sub E/ with Imp 7

Journal Article · Sat May 01 04:00:00 EDT 1976 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA081i013p02341· OSTI ID:7270134

Sarris, E T; Krimigis, S M; Armstrong, T P

A detailed study of energetic (E/sub p/> approx.0.29 MeV; E/sub e/> approx.0.22 MeV) proton and electron bursts in the vicinity of the magnetosphere over a 1-year period using the Johns Hopkins University/Applied Physics Laboratory experiment on board the near-circular orbiting Explorer 47 (Imp 7) satellite has been performed with greater sensitivity than has previously been possible. The results reveal that bursts of electrons and protons at these energies are a semipermanent feature of the near-earth environment, with intensities ranging from 10/sup -2/ to 10/sup 4/ (cm/sup 2/ s sr MeV)/sup -1/ for protons and 0.5 to 5 x 10/sup 3/ (cm/sup 2/ s sr)/sup -1/ for electrons and energies up to 4.5 MeV and >1 MeV for protons and electrons, respectively. The bursts are found in and about the magnetosheath, plasma sheet, and magnetotail boundary layer and outside the bow shock; however, they rarely appear at large distances (greater than about 10 R/sub E/) north or south of the neutral sheet. Dawn--dusk asymmetries are present in intensity but not necessarily in frequency of occurrence. Proton bursts are highly anisotropic upstream from the bow shock and in the magnetosheath. In the magnetotail, proton anisotropies are somewhat reduced and are directed toward or away from the earth but with a substantial dawn to dusk component. Electron bursts are anisotropic only in the upstream solar wind. A unique class of 'impulsive' bursts has been identified in the dusk magnetotail having intensities of up to 10/sup 5/ (cm/sup 2/ s sr MeV)/sup -1/, a duration of 10--30 s, and field-aligned anisotropies of up to 5 x 10/sup 4/ to 1 (sunward to antisunward ratio) and exhibiting inverse velocity dispersion. No electrons are observed with these bursts. The observed bursts are consistent with a nonthermal origin, in association with other magnetospheric phenomena. The implications of the results with regard to the origin of the bursts, acceleration mechanisms, and magnetospheric processes in general are discussed. (AIP)

• Research Organization: Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland 20810
• OSTI ID: 7270134
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 81:13; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640203* -- Atmospheric Physics-- Magnetospheric Phenomena-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANISOTROPY
BARYONS
ELECTRONS
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
HADRONS
IMP SATELLITES
KEV RANGE
KEV RANGE 100-1000
LEPTONS
MAGNETOSHEATH
MAGNETOTAIL
NUCLEONS
PLASMA SHEET
PROTONS
SATELLITES