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Ann. Geophys., 22, 1787-1798, 2004
www.ann-geophys.net/22/1787/2004/
© European Geosciences Union 2004
On the altitude dependence of transversely heated O+ distributions in the cusp/cleft
M. Bouhram1, B. Klecker1, W. Miyake2, H. Rème3, J.-A. Sauvaud3, M. Malingre4, L. Kistler5, and A. Blăgău1,6
1Max-Planck-Institut für extraterrestrische Physik, Gießenbachstraße, D-85741 Garching, Germany
2Communications Research Laboratory, 4-2-1 Koganei, Tokyo 184-8795, Japan
3CESR-CNRS, BP-4346, 31028 Toulouse Cedex 04, France
4CETP-CNRS, 4 Avenue de Neptune, 94100 Saint-Maur Cedex, France
5Space Science Center, University of New Hampshire, Durham, USA
6Space Science Institute, R-76911 Bucharest, Romaniadex, France
Abstract. The present paper focuses on the altitude dependence of
oxygen ion conics in the dayside cusp/cleft region. Here, combining oxygen
data from the Akebono, Interball-2 and Cluster satellites allows, for the
first time, one to follow the global development of energetic (up to ~10keV)
ion outflow over a continuous and broad altitude range up to about 5.5
Earth radii (RE). According to earlier statistical studies, the
results are consistent with a height-integrated energization of ions at
altitudes up to 3.5 RE. Higher up, the results inferred from Cluster
observations put forward evidence of a saturation of both a transverse
energization rate and ion gyroradii. We suggest that such results may be
interpreted as finite perpendicular wavelength effects (a few tens of km) in
the wave-particle interactions. To substantiate the suggestion, we carry out
two-dimensional, Monte Carlo simulations of ion conic production that
incorporate such effects and limited residence times due to the finite
latitudinal extent of the heating region.
Key words. Magnetospheric physics (auroral phenomena) –
Space plasma physics (charged particle motion and acceleration;
wave-particle interactions)
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