|
|
 |
|
|
Ann. Geophys., 16, 698-710, 1998
www.ann-geophys.net/16/698/1998/
© European Geosciences Union 1998
Equatorial electrojet as part of the global circuit: a case-study from the IEEY
A. T. Kobea1, C. Amory-Mazaudier2, J. M. Do2, H. Lühr3, E. Houngninou1, J. Vassal2, E. Blanc4, and J. J. Curto5
1U. F. R. SSMT / Laboratoire de Physique de l'Atmosphère, 22 B.P. 582 Abidjan 22, Côte d'Ivoire Tel: 225 44 49 82; Fax: 225 44 49 82/44 38 47; e-mail: kobeat@syfed.ci.refer.org
2Centre d'Etudes des Environnements Terrestres et Planétaires(CETP), Observatoire de Saint-Maur. 4, avenue de Neptune, F-94107 Saint-Maur-Des-Fossés, France
3Institut für Geophysik und Meteorologie der Technischen Universität Braunschweig, Mendelssohnstrass 3, D-38106 Braunschweig, Germany
4Commissariat à l'Energie Atomique, Laboratoire de Détection et de Géophysique, BP 12, F-91680 Bruyères-le-Châtel, France
5Observatorio de Ebre, E-43520 Roquetes, Tarragona, Spain
Abstract. Geomagnetic storm-time variations often occur
coherently at high latitude and the day-side dip equator where they affect the
normal eastward Sq field. This paper presents an analysis of ground magnetic
field and ionospheric electrodynamic data related to the geomagnetic storm which
occured on 27 May 1993 during the International Equatorial Electrojet Year
(IEEY) experiment. This storm-signature analysis on the auroral, mid-latitude
and equatorial ground field and ionospheric electrodynamic data leads to the
identification of a sensitive response of the equatorial electrojet (EEJ) to
large-scale auroral return current: this response consists in a change of the
eastward electric field during the pre-sunrise hours (0400-0600 UT) coherently
to the high-, mid-, and equatorial-latitude H decrease and the
disappearance of the EEJ irregularities between the time-interval 0800-0950 UT.
Subsequent to the change in h'F during pre-sunrise hours, the observed foF2
increase revealed an enhancement of the equatorial ionization anomaly (EIA)
caused by the high-latitude penetrating electric field. The strengthening of
these irregularities attested by the Doppler frequency increase tracks the H
component at the equator which undergoes a rapid increase around 0800 UT. The
∆H variations observed at the equator are the sum of the
following components: SR, DP, DR, DCF and
DT.
Keywords. Equatorial electrojet ·
Magnetosphere-ionosphere interactions · Electric fields and currents · Auroral
ionosphere · Ionospheric disturbances
Full Article in PDF (536 KB) |
|
|
