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Ann. Geophys., 22, 2441-2450, 2004
www.ann-geophys.net/22/2441/2004/
© European Geosciences Union 2004
Spatial and temporal variations of the high-altitude cusp precipitation
Z. Němeček, J. Šimůnek, J. Šafránková, and L. Přech
Charles University, Faculty of Mathematics and Physics, Prague, Czech Republic
Abstract. Structured dispersion patterns of the ion precipitation in low- and mid-altitude
cusp regions have been reported by many authors.
These patterns are interpreted either as temporal features in terms of the
pulsed reconnection model or as spatial changes caused by a combination of the
particle velocity with the convection of magnetic field lines.
It is generally expected that the spatial dispersion
is predominantly observed in lower altitudes where the spacecraft crosses a wide
range of geomagnetic coordinates in a short time,
whereas the high-altitude spacecraft observes temporal changes because it stays
nearly on the same field line for a long time.
We have analyzed one pass of the INTERBALL-1/MAGION-4
satellite pair through the high-altitude cusp and found that both
temporal and spatial dispersion effects are important even in
the magnetopause vicinity. The analysis of the present event shows a spatial
nature of the observed dispersion in the LLBL and in the plasma mantle. We have
identified two sources of a mantle precipitation operating simultaneously.
Our investigations suggest that besides
already reported latitudinal dispersion, the longitudinal
dispersion can be observed during intervals of sufficiently high
east-west interplanetary magnetic field component.
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