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| Titel |
Proton isotropy boundaries as measured on mid- and low-altitude satellites |
| VerfasserIn |
N. Yu. Ganushkina, T. I. Pulkkinen, M. V. Kubyshkina, V. A. Sergeev, E. A. Lvova, T. A. Yahnina, A. G. Yahnin, T. Fritz |
| 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 ; 23, no. 5 ; Nr. 23, no. 5 (2005-07-28), S.1839-1847 |
| Datensatznummer |
250015270
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| Publikation (Nr.) |
 copernicus.org/angeo-23-1839-2005.pdf |
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| Zusammenfassung |
| Polar CAMMICE MICS proton pitch angle distributions with
energies of 31-80 keV were analyzed to determine the
locations where anisotropic pitch angle distributions
(perpendicular flux dominating) change to isotropic
distributions. We compared the positions of these mid-altitude
isotropic distribution boundaries (IDB) for different activity
conditions with low-altitude isotropic boundaries (IB) observed
by NOAA 12. Although the obtained statistical properties of IDBs
were quite similar to those of IBs, a small difference in
latitudes, most pronounced on the nightside and dayside, was
found. We selected several events during which simultaneous
observations in the same local time sector were available from
Polar at mid-altitudes, and NOAA or DMSP at low-altitudes.
Magnetic field mapping using the Tsyganenko T01 model with the
observed solar wind input parameters showed that the low- and
mid-altitude isotropization boundaries were closely located,
which leads us to suggest that the Polar IDB and low-altitude
IBs are related. Furthermore, we introduced a procedure to control
the difference between the observed and model magnetic field to
reduce the large scatter in the mapping. We showed that the
isotropic distribution boundary (IDB) lies in the region where
Rc/ρ~6, that is at the boundary of the region
where the non-adiabatic pitch angle scattering is strong enough.
We therefore conclude that the scattering in the large field
line curvature regions in the nightside current sheet is the
main mechanism producing isotropization for the main portion
of proton population in the tail current sheet. This mechanism
controls the observed positions of both IB and IDB boundaries.
Thus, this tail region can be probed, in its turn, with
observations of these isotropy boundaries.
Keywords. Magnetospheric physics (Energetic particles,
Precipitating; Magnetospheric configuration and dynamics;
Magnetotail) |
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