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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, A08308, doi:10.1029/2006JA012192, 2007

Response of the equatorial ionosphere at dusk to penetration electric fields during intense magnetic storms

S. Basu

Space Physics Directorate, Air Force Research Laboratory, Hanscom AFB, Massachusetts, USA


Su. Basu

Center for Space Physics, Boston University, Boston, Massachusetts, USA


F. J. Rich

Space Physics Directorate, Air Force Research Laboratory, Hanscom AFB, Massachusetts, USA


K. M. Groves

Space Physics Directorate, Air Force Research Laboratory, Hanscom AFB, Massachusetts, USA


E. MacKenzie

Institute for Scientific Research, Boston College, Chestnut Hill, Massachusetts, USA


C. Coker

Naval Research Laboratory, Washington, District of Columbia, USA


Y. Sahai

Universidade do Vale do Paraíba, São José dos Campos, São Paulo, Brazil


P. R. Fagundes

Universidade do Vale do Paraíba, São José dos Campos, São Paulo, Brazil


F. Becker-Guedes

Universidade do Vale do Paraíba, São José dos Campos, São Paulo, Brazil


Abstract

We investigate the response of the equatorial ionosphere at dusk to the intense magnetic storms of 30 October 2003 and 20 November 2003, different aspects of which have been widely studied by the community. We present here a very complete set of space and ground-based diagnostics that provide the vertical and latitudinal structures of the ionosphere within the South Atlantic magnetic anomaly (SAMA) region and the contiguous parts of South America and Africa. We show that for both storms, the dusk sector corresponding to the universal time (UT) interval between the fast decrease of the SYM-H index and minimum SYM-H value determines uniquely the longitude interval populated by equatorial plasma bubbles and depletions. Further, we find that the UT of these storms is such that the ionospheric density perturbations occur in the SAMA region, which are most extended in latitude and altitude compared with other regions of the globe. In the dusk sector, the eastward penetration electric field, associated with rapid SYM-H decrease, adds to the postsunset eastward E-field because of the F region dynamo, which may be specially enhanced in this longitude interval because of the increased zonal conductivity gradient caused by energetic particle precipitation. This enhanced E-field at dusk causes a rapid uplift of the ionosphere and sets off plasma instabilities to form bubbles or bite-outs. The decreased ion density seen in the Defense Meteorological Satellite Program (DMSP) in situ data at 840 km indicates that the ionospheric plasma has been lifted above the DMSP altitude and transported away from the region by diffusion along magnetic field lines. Plasma bubbles and bite-outs impact satellite communication and navigation systems by introducing scintillations and steep density gradients. This paper corroborates that intense magnetic storms follow the framework, developed by Su. Basu et al. (2001) for moderate storms, that specifies the longitude interval in which such disturbances are most likely to occur.

Received 26 November 2006; accepted 19 June 2007; published 25 August 2007.

Keywords: Equatorial ionosphere; magnetic storms; plasma structuring.

Index Terms: 2415 Ionosphere: Equatorial ionosphere; 2788 Magnetospheric Physics: Magnetic storms and substorms (7954); 2439 Ionosphere: Ionospheric irregularities; 2736 Magnetospheric Physics: Magnetosphere/ionosphere interactions (2431); 7934 Space Weather: Impacts on technological systems.

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Citation: Basu, S., Su. Basu, F. J. Rich, K. M. Groves, E. MacKenzie, C. Coker, Y. Sahai, P. R. Fagundes, and F. Becker-Guedes (2007), Response of the equatorial ionosphere at dusk to penetration electric fields during intense magnetic storms, J. Geophys. Res., 112, A08308, doi:10.1029/2006JA012192.