HR: 12:05h
AN: SM41D-08    [PDF]
TI: Storm-time Energetic O+ Flux Variations in the Ring Current and the Plasmasheet: A Study of the April 2002 Storm Event
AU: * Ohtani, S
EM: ohtani@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, 20723-6099 United States
AU: C:son Brandt, P
EM: brandpc1@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, 20723-6099 United States
AU: Mitchell, D G
EM: Donald.G.Mitchell@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, 20723-6099 United States
AU: Nose', M
EM: nose@kugi.kyoto-u.ac.jp
AF: Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502 Japan
AU: Singer, H
EM: Howard.Singer@noaa.gov
AF: NOAA R/E/SE, 325 Broadway, Boulder, CO 80303-3328 United States
AU: Reeves, G
EM: reeves@nis.lanl.gov
AF: Los Alamos National Laboratory, Mail Stop D-466, Los Alamos, NM 87544 United States
AB: The development of the ring current during intense magnetospheric storms is often discussed in terms of the energization of single-charged oxygen ions. Although it is generally accepted that the ionosphere is the ultimate source of such O+ ions, it still remains to be understood where and how they are accelerated in the magnetosphere. The present study examines global changes of oxygen ENA fluxes measured by the IMAGE/HENA instrument. A focus is placed on a storm event that took place in April 2002. When the IMAGE satellite was at vantage points during this storm event, it occasionally observed the oxygen ENA flux to increase globally within 10 min or less in the ring current region. This timescale is too short for those O+ ions to be transported from the plasmasheet. In situ measurements of magnetic field and energetic particle fluxes at geosynchronous orbit reveal simultaneous occurrence of dipolarization and particle injection. The Geotail satellite, which was located in the postmidnight magnetotail, also observed an increase of the O+/H+ ratio in the energy density in association with substorm activity. The present result indicates that the substorm-associated local acceleration is crucial for the energization of the ring-current O+ ions at storm time.
DE: 2720 Energetic particles, trapped
DE: 2760 Plasma convection
DE: 2764 Plasma sheet
DE: 2778 Ring current
DE: 2788 Storms and substorms
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting