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| Titel |
Relationships between field-aligned currents and convection observed by EISCAT and implications concerning the mechanism that produces region-2 currents: Statistical study |
| VerfasserIn |
Christophe Peymirat, Dominique Fontaine |
| 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 ; 12, no. 4 ; Nr. 12, no. 4, S.304-315 |
| Datensatznummer |
250010683
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| Publikation (Nr.) |
 copernicus.org/angeo-12-304-1994.pdf |
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| Zusammenfassung |
| Fluid theories explain the origin of region-2
field-aligned currents as the closure of the ring current, driven itself by the
azimuthal pressure gradients generated in the magnetospheric ring plasma by the
sunward convection. Although the structure of pressure gradients appears
experimentally complex, observations confirm that a close connection exists
between the region-2 field-aligned currents and the ring current. The fluid
linear theory of the adiabatic transport by convection of the ring plasma gives
a first estimate of this process, and leads ultimately to phase quadrature (in
terms of magnetic local time) between the region-2 field-aligned currents and
the convection potential. When significant non-adiabatic processes are taken
into account, such as precipitations at auroral latitudes, the theoretical phase
difference rotates toward opposition. We determine experimentally the phase
relationship between the region-2 field-aligned currents and the convection
potential from recent statistics, depending on the magnetic activity index Kp,
and performed from the EISCAT data base. For geometrical reasons of sufficient
probing of region 2, it is only computed in the case of a moderate magnetic
activity corresponding to 2 ≤ Kp<4. Region-2 field-aligned
currents are found to be in phase opposition with the convection electrostatic
potential at auroral latitudes. This confirms the importance of non adiabatic
processes, especially ion losses, in the generation of region-2 field-aligned
currents, as theoretically suggested. |
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