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Ann. Geophys., 21, 1939-1946, 2003
www.ann-geophys.net/21/1939/2003/
© European Geosciences Union 2003
Dynamic processes and kinetic structure of collisionless reconnection at the dayside magnetopause: comparison between GEOTAIL observations and computer simulations
X. H. Deng1,2, H. Matsumoto2, H. Kojima2, R. R. Anderson2,3, T. Mukai4, and J. F. Wang1
1School of Electronics and Information , Wuhan University, Wuhan, 430079, P. R. China
2Radio Science Center for Space and Atmosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
3The University of Iowa, Iowa City, Iowa 52242, USA
4Institute of Space and Astronautical Science, Sagamihara, Kanagawa 229-8510, Japan
Abstract. In this paper we report
new kinetic features of ions and electrons observed in the vicinity of the
reconnection layer on 10 January 1997. This event has a three-dimensional
magnetic field topological structure, which is much more complex than the
previously suggested two-dimensional magnetic configuration. The ion
distributions are non-gyrotropic and electrons show non-Maxwellian distribution
functions. Acceleration of multiple ion beams, both parallel and perpendicular
to the local magnetic field, have been observed. The perpendicular acceleration
of the multiple ion beams can be explained by plasma mixing between the
meandering ions accelerated around the ion diffusion region and the cold ions
convected directly from the magnetosheath without passing through the X-line
region. The parallel acceleration of the multiple ion beams can be understood
by the fact that high-velocity ions ejected from the vicinity of the X-line mix
with the plasma flowing directly across the boundary. We observed the kinetic
effect of the separation of the electron and ion edges due to the
time-of-flight effect. It is stressed that kinetic processes are the key to
understanding these new observations that cannot be adequately explained by
magnetohydrodynamic (MHD) models.
Key words. Space plasma physics
(magnetic reconnection; charged particle motion and acceleration) –
Magnetospheric physics (magnetopause, cusp, and boundary layers)
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