 |
| Titel |
The dynamics and relationships of precipitation, temperature and convection boundaries in the dayside auroral ionosphere |
| VerfasserIn |
J. Moen, M. Lockwood, K. Oksavik, H. C. Carlson, W. F. Denig, A. P. Eyken, I. W. McCrea |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 22, no. 6 ; Nr. 22, no. 6 (2004-06-14), S.1973-1987 |
| Datensatznummer |
250014891
|
| Publikation (Nr.) |
 copernicus.org/angeo-22-1973-2004.pdf |
|
|
|
|
|
| Zusammenfassung |
| A continuous band of high ion temperature, which
persisted for about 8h and zigzagged north-south across more than five
degrees in latitude in the dayside (07:00-15:00MLT) auroral ionosphere, was
observed by the EISCAT VHF radar on 23 November 1999. Latitudinal gradients
in the temperature of the F-region electron and ion gases (Te and
Ti, respectively) have been compared with concurrent observations of
particle precipitation and field-perpendicular convection by DMSP
satellites, in order to reveal a physical explanation for the
persistent band of high Ti, and to test the potential role of Ti
and Te gradients as possible markers for the open-closed field line
boundary. The north/south movement of the equatorward Ti boundary was
found to be consistent with the contraction/expansion of the polar cap due to
an unbalanced dayside and nightside reconnection. Sporadic intensifications in
Ti, recurring on ~10-min time scales, indicate that frictional
heating was modulated by time-varying reconnection, and the band of high
Ti was located on open flux. However, the equatorward Ti boundary
was not found to be a close proxy of the open-closed boundary. The closest
definable proxy of the open-closed boundary is the magnetosheath electron
edge observed by DMSP. Although Te appears to be sensitive to magnetosheath
electron fluxes, it is not found to be a suitable parameter for routine
tracking of the open-closed boundary, as it involves case dependent analysis
of the thermal balance. Finally, we have documented a region of newly-opened
sunward convecting flux. This region is situated between the convection
reversal boundary and the magnetosheath electron edge defining the
open-closed boundary. This is consistent with a delay of several minutes
between the arrival of the first (super-Alfvénic) magnetosheath
electrons and the response in the ionospheric convection, conveyed to the
ionosphere by the interior Alfvén wave. It represents a candidate
footprint of the low-latitude boundary mixing layer on sunward convecting
open flux. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|