IUGG99 - 0900-33 GA3.05/W/25-B3 Poster F FENNELL, J L Roeder , J B Blake; R. H. W. Friedel, G. D. Reeves and M. Henderson; M. Grande; T. A. Fritz; S. Livi


J F FENNELL, J L Roeder , J B Blake (The Aerospace Corporation, Los Angeles, CA, 90009, USA, email joseph.f.fennell@aero.org) R. H. W. Friedel, G. D. Reeves and M. Henderson (Los Alamos National Laboratory, MS: D436, Los Alamos, NM 87545, United States) M. Grande (Rutherford Appleton Laboratory, Chilton-Didcot, OX110QX, United Kingdom) T. A. Fritz(Boston University, Boston, MA 02215, United States) S. Livi (Max Planck Institute for Aeronomy, Katlenburg-Lindau, Germany)

One of the problems of performing ring current studies with in-situ data has been the poor spatial/temporal sampling of the inner magnetosphere that has been provided by single satellite studies. Generally, the recent (since 1984) studies of the ring current have relied on single satellites in geotransfer or higher apogee orbits with periods of 10 hours or more. The recent observations taken by the Polar satellite in an 18 hour orbit are representative of this problem. For this study we combine the detailed composition observations from Polar CAMMICE experiment with proton observations by HEO (94-026, 95-034, and 97-068) satellites in ~12 hour orbits at different local times. The HEO coverage occurs roughly in the pre-noon/pre-midnight, post-noon/post-midnight and dawn/ dusk regions of the inner magnetosphere. Polar covers the pre-noon/pre-midnight region. The minimum Dst ~ -216 nT occurred on May 4, 1998 near 0530 UT. Polar was outbound through the near noon ring current region from ~0400 UT until it exited the plasma sheet and entered the magnetosheath (during the shock) near 0615 and again near 0645 UT. It did not resample the ring current until after 1920 UT on May 4. Adding the HEO data provides ring current traversals near 0000, 0500, 0600, 0800, 0830,1100, and 1400 UT on May 4 during the DST minimum and early storm recovery. These data are combined to provide a picture of the evolution of the ring current as a map of its peak position and outer and inner edges as a function of time and local time. The combined observations will be presented and discussed in terms of the development of the storm main phase and its initial recovery.