Observations of energetic radiation belt helium ions at the geomagnetic equator during quiet conditions
Fluxes of geomagnetically trapped energetic helium ions in the immediate vicinity of the geomagnetic equator have been unambiguously identified and measured with Explorer 45. The observations presented span and L shell range 2.25< or approx. =L< or approx. =5 and extend the observational coverage of radiation belt helium ions. During geomagnetically quiescent conditions these fluxes are found to peak sharply near L=3.25 with equatorially mirroring intensities of 80 and 34 ions/cm/sup 2/ s sr keV in the 1.16-1.74 MeV and 1.74-3.15 MeV per particle passbands, respectively. The helium ion fluxes are observed to exhibit a significant B/B/sub 0/ dependence and indicate that the ion flux pitch angle distribution j (..cap alpha..) is very anisotropic. If j (..cap alpha..) approx. =j/sub perpendicular/ sin/sup m/ ..cap alpha.., then m values of 8 and 10 correspond to the responses of the two passbands within the B/B/sub 0/ range of 1.0-1.4 observed. When the B/B/sub 0/ dependence is removed, the fluxes exhibit no detectable decay over a 2-week period covered by the study.
- Research Organization:
- Space Environment Laboratory, NOAA Environmental Research Laboratories, Boulder, Colorado 80303
- OSTI ID:
- 6673191
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 83:A6
- Country of Publication:
- United States
- Language:
- English
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