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Ann. Geophys., 17, 1611-1621, 1999
www.ann-geophys.net/17/1611/1999/
© European Geosciences Union 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
1Space Science Center, Morse Hall, University of New Hampshire, Durham, NH, USA
E-mail: Lynn.kistler@uhn.edu
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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