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| Titel |
Spatial structure of the plasma sheet boundary layer at distances greater than 180 RE as derived from energetic particle measurements on GEOTAIL |
| VerfasserIn |
D. V. Sarafopoulos, E. T. Sarris, V. Angelopoulos, T. Yamamoto, S. Kokubun |
| 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 ; 15, no. 10 ; Nr. 15, no. 10, S.1246-1256 |
| Datensatznummer |
250012971
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| Publikation (Nr.) |
 copernicus.org/angeo-15-1246-1997.pdf |
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| Zusammenfassung |
| We have analyzed the onsets of energetic
particle bursts detected by the ICS and STICS sensors of the EPIC instrument on
board the GEOTAIL spacecraft in the deep magnetotail (i.e., at distances greater
than 180 RE). Such bursts are commonly observed at the plasma-sheet
boundary layer (PSBL) and are highly collimated along the magnetic field. The
bursts display a normal velocity dispersion (i.e., the higher-speed particles
are seen first, while the progressively lower speed particles are seen later)
when observed upon entry of the spacecraft from the magnetotail lobes into the
plasma sheet. Upon exit from the plasma sheet a reverse velocity dispersion is
observed (i.e., lower-speed particles disappear first and higher-speed particles
disappear last). Three major findings are as follows. First, the tailward-jetting
energetic particle populations of the distant-tail plasma sheet display an
energy layering: the energetic electrons stream along open PSBL field lines with
peak fluxes at the lobes. Energetic protons occupy the next layer, and as the
spacecraft moves towards the neutral sheet progressively decreasing energies are
encountered systematically. These plasma-sheet layers display spatial symmetry,
with the plane of symmetry the neutral sheet. Second, if we consider the same
energy level of energetic particles, then the H+ layer is confined
within that of the energetic electron, the He++ layer is confined
within that of the proton, and the oxygen layer is confined within the alpha
particle layer. Third, whenever the energetic electrons show higher fluxes
inside the plasma sheet as compared to those at the boundary layer, their
angular distribution is isotropic irrespective of the Earthward or tailward
character of fluxes, suggesting a closed field line topology. |
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