Articles | Volume 17, issue 12
Ann. Geophys., 17, 1611–1621, 1999

Special issue: Equator S

Ann. Geophys., 17, 1611–1621, 1999

  31 Dec 1999

31 Dec 1999

Testing electric field models using ring current ion energy spectra from the Equator-S ion composition (ESIC) instrument

L. M. Kistler1, B. Klecker2, V. K. Jordanova1, E. Möbius1, M. A. Popecki1, D. Patel1, J. A. Sauvaud3, H. Rème3, A. M. Di Lellis4, A. Korth5, M. McCarthy6, R. Cerulli4, M. B. Bavassano Cattaneo4, L. Eliasson7, C. W. Carlson8, G. K. Parks6, G. Paschmann2, W. Baumjohann2, and G. Haerendel2 L. M. Kistler et al.
  • 1Space Science Center, Morse Hall, University of New Hampshire, Durham, NH, USA
  • E-mail:
  • 2Max-Planck-Institut für Extraterrestriche Physik, Garching, Germany
  • 3C.E.S.R.., Toulouse, France
  • 4I.F.S.I, Rome, Italy
  • 5Max-Planck-Institut für Aeronomie, Katlinberg-Lindau, Germany
  • 6University of Washington, Seattle, WA, USA
  • 7Swedish Institute of Space Physics, Kiruna, Sweden
  • 8University of California, Berkeley, CA, USA

Abstract. During the main and early recovery phase of a geomagnetic storm on February 18, 1998, the Equator-S ion composition instrument (ESIC) observed spectral features which typically represent the differences in loss along the drift path in the energy range (5–15 keV/e) where the drift changes from being E × B dominated to being gradient and curvature drift dominated. We compare the expected energy spectra modeled using a Volland-Stern electric field and a Weimer electric field, assuming charge exchange along the drift path, with the observed energy spectra for H+ and O+. We find that using the Weimer electric field gives much better agreement with the spectral features, and with the observed losses. Neither model, however, accurately predicts the energies of the observed minima.

Key words. Magnetospheric physics (energetic particles trapped; plasma convection; storms and substorms)

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