Observations of >100-keV protons in the earth's magnetosheath

Journal Article · Sun Feb 01 04:00:00 EST 1976 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA081i004p00569· OSTI ID:7285712

West, Jr, H I; Buck, R M

Bursts of energetic protons, 100--1300 keV, were observed on Ogo 5 in the magnetosheath and upstream wave region beyond the earth's bow shock during periods of generally enhanced solar and magnetic activity in 1968. From these data, a comprehensive study of energetic protons in the magnetosheath is presented. These magnetosheath protons are found to be directional with the peak flux directed downstream. Typical downstream-to-upstream flux ratios are from 10/1 to 20/1 in most regions but often as great as 100/1 near the afternoon magnetopause. The fluxes correlate roughly with magnetic activity. The downstream flux can be expressed as j (>100 keV) =500 x 10/sup 0/./sup 412//cm/sup 2/ sr s to about an order of magnitude. Peak unidirectional fluxes near the magnetopause are often similar in spectra and intensity to the peak intensities of trapped fluxes in the nearby magnetosphere. Enhanced proton fluxes occur in the sheath in correlation with depressions in the sheath magnetic field and in correlation with enhanced turbulence. Often at such times, magnetopause boundary layer effects are observed. Energetic proton bursts are also observed in the upstream wave region beyond the shock, predominately on the morning side of the earth. They correlate well with the wave observations; however, on occasion, they are offset as much as 10 min in time. Directional observations indicate downstream-to-upstream directed flux ratios of 10/1 as being typical of the upstream wave region. The directional anisotropies in both the sheath and the upstream wave regions are largely explained by combinations of the Compton-Getting effect, proton flux spatial gradients, and the free streaming of protons along field lines from an upstream source region. Possible sources of the energetic magnetosheath protons are magnetospheric escape or the energization of low-energy protons in the magnetosheath, shock, and/or upstream wave region. No strong preference is ascribed to any one source. (AIP)

• Research Organization: Lawrence Livermore Laboratory, University of California, Livermore, California 94550
• OSTI ID: 7285712
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 81:4; 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
CHARGED-PARTICLE PRECIPITATION
ENERGY RANGE
FLUX DENSITY
KEV RANGE
KEV RANGE 100-1000
MAGNETOPAUSE
MAGNETOSHEATH
OGO SATELLITES
PROTON PRECIPITATION
SATELLITES
SOLAR ACTIVITY
SOLAR WIND