Showing papers by "Inez S. Batista published in 2014"

Equatorial ionization anomaly variability over the Brazilian region during boreal sudden stratospheric warming events

Abstract: This study refers to the connection between the stratosphere and ionosphere, investigating, specifically, the behavior of the equatorial ionization anomaly (EIA) and ionospheric effects over the Brazilian region during sudden stratospheric warming (SSW) events. We studied three major warmings that occurred in the Northern Hemisphere winter 2007–2008, 2008–2009, and 2009–2010 and a minor warming that occurred in 2010–2011. The solar activity was low for the first two cases and relatively moderate for the last two. In this study the EIA behavior was investigated using the ΔTEC (total electron content) parameter, which expresses the EIA relative intensity for the Brazilian sector. The results for the Brazilian region show, mainly after SSW temperature peak, an increase in the EIA intensity in the morning, followed by a decrease in the afternoon. As identified through ΔTEC signatures and consistently confirmed through wavelet power spectra analysis, this semidiurnal behavior is preserved for a number of days equal to the polar region thermal stabilization phase and it is very similar to the results obtained in pioneer studies in the Peruvian sector, in which TEC data was also used. In some cases the TEC negative variation is stronger than the positive, being noticeably more intense around the prereversal enhancement time, when the EIA is strongly suppressed in the Brazilian sector.

Equatorial broad plasma depletions associated with the enhanced fountain effect

Abstract: [1] Broad plasma depletions (BPDs), plasma depletions whose longitudinal width is over several hundred kilometers, have been detected in the equatorial F region by low-earth-orbit satellites during both magnetically quiet and magnetically disturbed periods. A few hypotheses were suggested to explain the creation of BPDs, but the underlying mechanism of this phenomenon is still under debate. We investigate the origin of BPDs by analyzing the simultaneous in situ and optical observations of the ionosphere on 30 May 2003 (Kp = 8+), 24 April 2012 (Kp = 7−), and 31 October 2012 (Kp = 0+). BPDs on 30 May 2003 were detected by the Republic of China Satellite-1 at an altitude of 600 km, and BPDs on the other days were detected by the Communication/Navigation Outage Forecasting System satellite near an altitude of 400 km. Our results show that the detection of BPDs is closely associated with background ionospheric morphology; BPDs are detected on the days when the equatorial ionization anomaly (EIA) is intense and the crests of the EIA have moved poleward. Measurements of upward plasma motion support the existence of ionospheric uplift at BPD locations. These observations and the detection of BPDs near the magnetic equator lead to the interpretation that the satellite detection of BPDs during those 3 days is likely related to the uplift of the F peak height above the satellite orbits.