Chen, J.,
Co-Authors: and T.A. Fritz,
Title: May 4, 1998 storm: Observations of energetic ion composition by POLAR,
Reference: Geophys. Res. Lett., 26, 2921-2941, 1999.
Reference Type: Published Journal
CEPPAD: true
CAMMICE: true
RAPID: false
Abstract:
A major geomagnetic storm occurred at 5:00-12:05 UT on May 4, 1998. During this period, the magnetosphere was compressed and eroded; POLAR traveled in its outbound orbit from the equatorial radiation belt to the cusp and crossed the magnetopause into the magnetosheath. Two CEP-like (Cusp Energetic Particle) events with two or three orders of magnitudes enhancements of MeV ion fluxes were measured. The first event had a peak flux higher than that of the intense outer radiation belt in the equatorial plane. The shape of the measured energy spectra (in the unit of keV/e) were ion species dependent. For He+/He++ ratio at 18-269 keV/e, the difference between the radiation belt and the magnetosheath can be by a factor of as large as 62. In the magnetosheath, the 18-269 keV/e ion composition are variable, indicating a mass dependent acceleration process. These MeV ions may be energized by a mechanism in the cusp responsible for the CEP events previously reported. !
