Observations of energetic helium ions in the Earth's radiation belts during a sequence of geomagnetic storms
Every year a significant number of magnetic storms disturb the earth's magnetosphere and the trapped particle populations. In this paper, we present observations of energetic (MeV) helium ions made with Explorer 45 during a sequence of magnetic storms during June through December of 1972. The first of these storms started on June 17 and had a Dst index excursion to approx.190 gamma, and the MeV helium ions were perturbed primarily beyond 3 earth radii in the equatorial radiation belts with a typical flux increase of an order of magnitude at L = 4. The second storm period took place during August and was associated with very major solar flare activity. Although the Dst extremum was at best 35 gamma less than the June storm, this period can be characterized as irregular (or multi-storm) with strong compression of the magnetosphere and very large (order of magnitude) MeV helium ion flux enhancements down to Lapprox.2. Following this injection the trapped helium ion fluxes showed positive spectral slope with the peak beyond 3.15 MeV at L = 2.5; and at the lowest observable L shells (Lapprox.2--3) little flux decay (tau>100 days) was seen during the rest of the year. Any effects of two subsequent major magnetic storms in September and November were essentially undetectable in the prolonged after-effect of the August solar flare associated MeV helium ion injection. The helium ion radial profile of the phase space density showed a significant negative slope during this period, and we infer that radial diffusion constitutes a significant loss of helium ions on L shells above Lapprox. =4 during the aftermath of the August 1972 magnetic storm(s).
- Research Organization:
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80302
- OSTI ID:
- 6385032
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 86:A4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
RADIATION BELTS
IONIC COMPOSITION
DISTURBANCES
EXPLORER SATELLITES
HELIUM IONS
MAGNETIC STORMS
MAGNETOSPHERE
SOLAR FLARES
CHARGED PARTICLES
EARTH ATMOSPHERE
IONS
SATELLITES
SOLAR ACTIVITY
640203* - Atmospheric Physics- Magnetospheric Phenomena- (-1987)