Spatial structure of the plasma sheet boundary layer at distances greater than 180 R<sub>E</sub> as derived from energetic particle measurements on GEOTAIL
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 R<sub>E</sub>). Such bursts are commonly observed at the plasma-sheet bou...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
1997-10-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/15/1246/1997/angeo-15-1246-1997.pdf |
| _version_ | 1818277623154868224 |
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| author | D. V. Sarafopoulos E. T. Sarris V. Angelopoulos T. Yamamoto S. Kokubun |
| author_facet | D. V. Sarafopoulos E. T. Sarris V. Angelopoulos T. Yamamoto S. Kokubun |
| author_sort | D. V. Sarafopoulos |
| collection | DOAJ |
| description | 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 R<sub>E</sub>). 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<sup>+</sup> layer is confined
within that of the energetic electron, the He<sup>++</sup> 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. |
| first_indexed | 2024-12-12T23:04:29Z |
| format | Article |
| id | doaj.art-c34807925a464e06aa51cd78c0defeb8 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-12T23:04:29Z |
| publishDate | 1997-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-c34807925a464e06aa51cd78c0defeb82022-12-22T00:08:44ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05761997-10-01151246125610.1007/s00585-997-1246-0Spatial structure of the plasma sheet boundary layer at distances greater than 180 R<sub>E</sub> as derived from energetic particle measurements on GEOTAILD. V. Sarafopoulos0E. T. Sarris1V. Angelopoulos2T. Yamamoto3S. Kokubun4Demokritos University of Thrace, Department of Electrical and Computer Engineering, Xanthi, GR-67100, GreeceDemokritos University of Thrace, Department of Electrical and Computer Engineering, Xanthi, GR-67100, GreeceSpace Sciences Laboratory, University of California, Berkeley, California, USAInstitute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara 229, JapanSolar-Terrestrial Environment Laboratory, Nagoya University, Toyokawa 442, JapanWe 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 R<sub>E</sub>). 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<sup>+</sup> layer is confined within that of the energetic electron, the He<sup>++</sup> 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.https://www.ann-geophys.net/15/1246/1997/angeo-15-1246-1997.pdf |
| spellingShingle | D. V. Sarafopoulos E. T. Sarris V. Angelopoulos T. Yamamoto S. Kokubun Spatial structure of the plasma sheet boundary layer at distances greater than 180 R<sub>E</sub> as derived from energetic particle measurements on GEOTAIL Annales Geophysicae |
| title | Spatial structure of the plasma sheet boundary layer at distances greater than 180 R<sub>E</sub> as derived from energetic particle measurements on GEOTAIL |
| title_full | Spatial structure of the plasma sheet boundary layer at distances greater than 180 R<sub>E</sub> as derived from energetic particle measurements on GEOTAIL |
| title_fullStr | Spatial structure of the plasma sheet boundary layer at distances greater than 180 R<sub>E</sub> as derived from energetic particle measurements on GEOTAIL |
| title_full_unstemmed | Spatial structure of the plasma sheet boundary layer at distances greater than 180 R<sub>E</sub> as derived from energetic particle measurements on GEOTAIL |
| title_short | Spatial structure of the plasma sheet boundary layer at distances greater than 180 R<sub>E</sub> as derived from energetic particle measurements on GEOTAIL |
| title_sort | spatial structure of the plasma sheet boundary layer at distances greater than 180 r sub e sub as derived from energetic particle measurements on geotail |
| url | https://www.ann-geophys.net/15/1246/1997/angeo-15-1246-1997.pdf |
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