The dynamics and relationships of precipitation, temperature and convection boundaries in the dayside auroral ionosphere

Moen, J., Lockwood, M. ORCID: https://orcid.org/0000-0002-7397-2172, Oksavik, K., Carlson, H. C., Denig, W. F., van Eyken, A. P. and McCrea, I. W. (2004) The dynamics and relationships of precipitation, temperature and convection boundaries in the dayside auroral ionosphere. Annales Geophysicae, 22 (6). pp. 1973-1987. ISSN 0992-7689 doi: 10.5194/angeo-22-1973-2004

Abstract/Summary

A continuous band of high ion temperature, which persisted for about 8 h 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 openclosed boundary. This is consistent with a delay of several minutes between the arrival of the first (super-Alfv´enic) magnetosheath electrons and the response in the ionospheric convection, conveyed to the ionosphere by the interior Alfv´en wave. It represents a candidate footprint of the low-latitude boundary mixing layer on sunward convecting open flux

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/38605
Identification Number/DOI	10.5194/angeo-22-1973-2004
Refereed	Yes
Divisions	No Reading authors. Back catalogue items Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	Copernicus Publications
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