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| Titel |
Modeling transverse heating and outflow of ionospheric ions from the dayside cusp/cleft. 2 Applications |
| VerfasserIn |
M. Bouhram, M. Malingre, J. R. Jasperse, N. Dubouloz, J.-A. Sauvaud |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 21, no. 8 ; Nr. 21, no. 8, S.1773-1791 |
| Datensatznummer |
250014677
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| Publikation (Nr.) |
 copernicus.org/angeo-21-1773-2003.pdf |
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| Zusammenfassung |
In this paper, we
consider major ion energization mechanisms in the dayside cusp/cleft region.
This includes transverse ion heating by ion cyclotron resonance (ICR), ion
energization through structures of field-aligned electric potential drops, and
transverse heating by lower hybrid (LH) waves. First, we present and discuss
three typical cusp/cleft crossings associated with one of the first two
mechanisms mentioned above. Then, we develop a procedure for finding the
altitude dependence of ICR heating for any data set in the high-altitude
cusp/cleft under the absence of field-aligned potential drops. This has been
accomplished using a large set of numerical simulations from a two-dimensional,
steady-state, Monte Carlo, trajectory-based code, as discussed in detail in the
first companion paper (Bouhram et al., 2003). The procedure is applied and
tested successfully for the first two events, by using patterns of ion moments
along the satellite track as constraints. Then, we present a statistical study
that uses 25 cusp/cleft crossings associated with steady IMF conditions, where
ICR heating is expected to occur alone. It is pointed out that the ICR heating
increases gradually versus geocentric distance as s 3.3 ± 1.8 . The inferred
values of the wave power and the spectral index associated with the component
responsible for ICR heating are lower than those characterizing the broad-band,
extremely low-frequency (BBELF) turbulence usually observed in the cusp/cleft.
This strengthens the idea that more than one wave-mode is contained in the
BBELF turbulence, and only a small fraction of the observed turbulence is
responsible for ICR heating. Then, we study the occurrence versus magnetic
local time (MLT) of field-aligned potential drops. According to previous
statistical studies, such structures are not common in the cusp and tend to be
associated with the cleft region. We also discuss the effects of LH heating in
the cusp on the observed ion distributions. However, this mechanism turns out
to be of less importance than ICR heating.
Key words. Magnetospheric physics (Auroral
phenomena) – Space plasma physics (charged particle motion and acceleration;
wave-particle interactions) |
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