Pitch angle distributions of geomagnetically trapped MeV Helium ions during quite times

Journal Article · Thu Jul 01 04:00:00 EDT 1982 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA087iA07p05095· OSTI ID:6716497

Fritz, T A; Spjeldvik, W N

During geomagnetically quite conditions energetic radiation belt helium ion fluxes at MeV energies have been found to exhibit characteristic radial profiles and large pitch angle anisotropies. Compiling data from many experiments we deduce a systematic dependence of this anisotropy with helium ion energy. When the observed pitch angle distributions are approximated by j(..cap alpha../sub 0/) = j/sub perpendicular/ sin/sup n/..cap alpha../sub 0/, ..cap alpha../sub 0/ being the equatorial pitch angle, an empirical relation n = 7+9.1 log/sub 10/(E), with the helium ion energy E, in MeV, is deduced over the energy range 0.59--9 MeV total ion energy (148--2250 keV per nucleon). These values are obtained for L shells in the range Lapprox.2 to 5, and possible radial variations of n are averaged over. The results are compared with theoretical expectations, and we suggest a qualitative explanation for the observed trend.

• Research Organization: Space Environment Laboratory, NOAA/ERL, Boulder, Colorado 80303
• OSTI ID: 6716497
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 87:A7; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640203* -- Atmospheric Physics-- Magnetospheric Phenomena-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHARGED PARTICLES
DISTRIBUTION FUNCTIONS
EARTH ATMOSPHERE
FUNCTIONS
GEOMAGNETIC FIELD
HELIUM IONS
INCLINATION
IONS
MAGNETIC FIELDS
MAGNETOSPHERE