Ionospheric Variability during Sudden Stratopheric Warmings over 60° Geomagnetic Meridian in the Brazilian Sector.

Abstract:

We present some evidence of the major Sudden Stratospheric Warming (SSW) events, which occurred during low solar activity of years 2008, 2009 and medium solar activity of 2013, as observed on Total Electron Content (TEC), MLT wind, and vertical plasma drift parameter. The Total Electron Content (TEC) was collected from the International Global Positioning System (IGS) and from the Brazilian Network of Continuous Monitoring (RBMC) stations. Daytime E´B vertical drift were derived from the magnetometers located at the equatorial station Alta Floresta (9.9ºS, 55.9ºW, dip lat: 1.96º) and an off equatorial station Cuiaba (15.3ºS, 56.0ºW, dip lat: 7.10º), both in the Brazilian sector, while the mesosphere and lower thermosphere (MLT) meridional and zonal wind components were measured by the Meteor Radar located at the southern mid-latitude Santa Maria (29.4ºS, 53.3ºW, dip lat: 17.8º) station. During the SSW events the GPS-TEC data exhibit a distinctive daytime and nighttime anomaly pattern with a suppression of Equatorial Ionization Anomaly (EIA) in the afternoon and enhancement of EIA during the morning hours. TEC was also characterized by semidiurnal and large amplitude, which lasted for several days mainly in 2008 and 2009 events. For 2013 event, we identify the anomalous variation in E´B drift based on later local time migration of peak value with SSW days. A novel feature of this study is the identification of the similar migration pattern in the TEC anomaly, in spite that the simultaneous solar-flux increases during the SSW event of 2013. Other novel features are the amplification of the 13-16 day periods in the TEC anomaly during the SSW days, and simultaneous amplification of these periods in the meridional and zonal wind components in the MLT region, as far as 30^o S. These aspects reveal the presence of coupled atmosphere-ionosphere dynamics during the SSW event and the amplification of the lunar and/or solar tidal component, a characteristic which is recently reported from the electrojet current measurements.