Regional differences of the ionospheric response to the July 2012 geomagnetic storm

Abstract

The July 2012 geomagnetic storm is an extreme space weather event in solar cycle 24, which is characterized by a southward interplanetary geomagnetic field lasting for about 30 h below −10 nT. In this work, multiple instrumental observations, including electron density from ionosondes, total electron content (TEC) from Global Positioning System, Jason‐2, and Gravity Recovery and Climate Experiment, and the topside ion concentration observed by the Defense Meteorological Satellite Program spacecraft are used to comprehensively present the regional differences of the ionospheric response to this event. In the Asian‐Australian sector, an intensive negative storm is detected near longitude ~120°E on 16 July, and in the topside ionosphere the negative phase is mainly existed in the equatorial region. The topside and bottomside TEC contribute equally to the depletion in TEC, and the disturbed electric fields make a reasonable contribution. On 15 July, the positive storm effects are stronger in the Eastside than in the Westside. The topside TEC make a major contribution to the enhancement in TEC for the positive phases, showing the important role of the equatorward neutral winds. For the American sector, the equatorial ionization anomaly intensification is stronger in the Westside than in the Eastside and shows the strongest feature in the longitude ~110°W. The combined effects of the disturbed electric fields, composition disturbances, and neutral winds cause the complex storm time features. Both the topside ion concentrations and TEC reveal the remarkable hemispheric asymmetry, which is mainly resulted from the asymmetry in neutral winds and composition disturbances.

New Aspects of the Ionospheric Behavior Over Millstone Hill During the 30‐Day Incoherent Scatter Radar Experiment in October 2002

“…Such zonal differences in the climatological ionosphere are explained in terms of the effect of magnetic declination modulated neutral winds. Under storm‐time circumstances, besides the regional differences at low latitudes reported by Kuai et al (), Thomas et al () presented strong zonal differences in the storm time ionosphere at middle latitudes.…”

“…The large EIA depletion is generally believed to be mainly the result of electric fields or wind changes, not disturbance neutral composition. A westward electric field was observed in the daytime equatorial and low‐latitude ionosphere (Kuai et al, ). Moreover, a strong zonal difference of storm time responses being observed in a narrow longitude region may possibly require the effects of the disturbed winds being modulated by magnetic field configurations during the storm.…”

Ionospheric Response to the St. Patrick's Day Space Weather Events in March 2012, 2013, and 2015 at Southern Low and Middle Latitudes

“…Liu et al () analyzed the ionospheric and thermospheric responses to the 15–16 July 2012 storm in the east Asian/Australian and the American sectors taking five stations from the Australian sector (including DW and BR stations) and found f o F 2 enhancements between 01 to 10 UT on 15 July over all the five sites followed by the long‐duration depressions in f o F 2 , which they accounted for neutral composition changes and DDEFs effects. Kuai et al (), taking same five stations from Australia, studied the differences in the ionospheric response of the 15–16 July 2012 geomagnetic storm in the Asian‐Australian (17 stations) and the American sectors. For the negative ionospheric storm in the Asian‐Australian sector, they suggested a greater contribution of DDEFs than the thermospheric neutral composition changes.…”

Chinese ionospheric investigations in 2016–2017

“…Investigations of this storm event have revealed several features and mechanisms. Kuai JW et al (2017) explored the latitudinal, longitudinal, and altitudinal differences for the July 2012 geomagnetic storm, using multiple instrumental observations, including electron density from ionosondes; total electron content (TEC) from Global Positioning System (GPS), Jason‐2, and Gravity Recovery and Climate Experiment (GRACE); and the topside ion concentrations observed by the Defense Meteorological Satellite Program (DMSP) spacecraft to present a comprehensive description of regional differences in the ionospheric response to this event. In the Asian‐Australian sector, on 16 July the data indicate an intensive negative storm near longitude ~120°E (as shown in Figure 1).…”

“…The decline of f o F 2 (in MHz) and the percentage of the relative decline in f o F 2 (compared with the geomagnetically quiet conditions) are given in the brackets. After Kuai JW et al (2017).…”