Study of simultaneous penetration of electric fields and variation of total electron content in the day and night sectors during the geomagnetic storm of 23 May 2002

[1] Evidence of simultaneous penetration of storm time electric fields in the day and night sectors of the globe during the geomagnetic storm of 23 May 2002 and the response of low-latitude ionosphere to such electric fields is presented. Using the ground-based magnetometer data, simultaneous penetrations of under-shielding and overshielding electric fields, and those arising owing to the unsteady ring currents, have been inferred in the day and night sectors. The ionospheric response in the day and night sectors near the northern crest of the equatorial ionization anomaly has been studied using total electron content (TEC) data. Multiple episodes of prompt penetration electric fields arising owing to the under-shielding and unsteady ring current conditions resulted in enhancement of the TEC in the day sector. These daytime TEC enhancements were reinforced by the equatorward neutral winds that also produced modulations in TEC. The presence of storm time equatorward neutral winds has been inferred from the increased thermospheric [O/N2] ratio. We also show, probably for the first time, that the same penetration fields in the night sector are responsible for the reductions in TEC on 23 May. Reduced TEC at 120°E longitude on 24 May, the day following the storm, has been attributed to the disturbance dynamo electric fields as well as to the changes in thermospheric chemical composition signified by reduced [O/N2] ratio.

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