Localized total electron content enhancements in the Southern Hemisphere

Ilya K Edemskiy

doi:10.5194/angeo-38-591-2020

Abstract

Abstract. This paper is dedicated to the investigation of localized TEC (total electron content) enhancements (LTEs), which were detected in the Southern Hemisphere via the analysis of global ionospheric maps. Using data from different years (2014, 2015 and 2018), we show the presence of LTEs almost independently of solar activity. We also show that LTEs are a phenomenon that can be observed in serial: at the same universal time (UT), similar enhancement can manifest themselves over several days. The intensity of LTEs varies depending on the solar flux and does not directly depend on the interplanetary magnetic field orientation; these events occur under both geomagnetically disturbed and quiet conditions. The highest LTE occurrence rate was observed during the period of local winter (April–September) in all years analyzed. The longest observed LTE series was detected during 2014 and lasted 80 d – or 120 d if we exclude two daily gaps.

Highlights

The Southern Hemisphere (SH) ionosphere has not been investigated as broadly as that of the Northern Hemisphere (NH): historically, most of the geophysical observations and measurements have been made north of the Equator
South of the South Atlantic Magnetic Anomaly (SAMA), in the southeastern Pacific and South Atlantic–Antarctic regions, the combination of the geomagnetic field features and thermospheric winds produces an inverted diurnal plasma density pattern at equinoxes and in the SH summer (October–March) – the nighttime maximum is larger than the daytime minimum – which is known as the Weddell Sea Anomaly (WSA; Horvath, 2006)
This paper shows that localized total electron content (TEC) enhancements in the SH are observed quite regularly and can be detected in serial

Summary

Introduction

The Southern Hemisphere (SH) ionosphere has not been investigated as broadly as that of the Northern Hemisphere (NH): historically, most of the geophysical observations and measurements have been made north of the Equator. Satellite measurements allow us to investigate the ionosphere over oceans; due to the high variability and the movement of satellites, it is very difficult to observe the same region under the same conditions. The South Atlantic Magnetic Anomaly (SAMA), for example, is formed by the configuration of the geomagnetic field which has a global intensity minimum over South Atlantic and South America that makes it easier for energetic particles of inner radiation belt to precipitate, thereby increasing the ionospheric conductivity over the region (Abdu et al, 2005). South of the SAMA, in the southeastern Pacific and South Atlantic–Antarctic regions, the combination of the geomagnetic field features and thermospheric winds produces an inverted diurnal plasma density pattern at equinoxes and in the SH summer (October–March) – the nighttime maximum is larger than the daytime minimum – which is known as the Weddell Sea Anomaly (WSA; Horvath, 2006). It is quite clear that the structure and dynamics of the ionosphere in both hemispheres should be different due to these anomalies and should be investigated separately

Results

Discussion

Conclusion