Topside ionospheric electron temperature and density along the Weddell Sea latitude

Abstract

It has been well known that the ionospheric electron density N e is greater in the summer nighttime than daytime around the Weddell Sea region, which is named Weddell Sea Anomaly (WSA). This paper for the first time reports unusual increases (decreases) of the daytime (nighttime) electron temperature T e at about 830 km altitude over the WSA latitudes probed by Tatiana-2 during December 2009 to January 2010. Concurrent measurements at 660-830 km altitude observed by Tatiana-2, Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER), and Formosa Satellite 3/Constellation Observing System for Meteorology, Ionosphere and Climate (F3/C) reveal the anticorrelation between T e and N e along the WSA latitudes in the daytime and nighttime. Based on F3/C N e along the WSA latitudes observed at various local times, the associated T e values are computed. The Tatiana-2 and DEMETER observations as well as the computed results show that T e yield the maximum values over the WSA region during daytime and over the Indian and Atlantic Ocean area during nighttime. The maxima or minima in F3/C N e and the computed T e reveal eastward phase shifts.

Three-dimensional electron density along the WSA and MSNA latitudes probed by FORMOSAT-3/COSMIC

“…Nevertheless, the simultaneous eastward shifts in the two plasma flows as well as ionospheric electron density and height confirm that the equatoward and upward plasma flows owing to neutral wind effects are the most essential. Jee et al (2009) observed that the electron density enhancement moves slightly eastward in the WSA region over the nighttime, while Liu et al (2014) and Chang et al (2012) showed the F3/C electron density with a global eastward phase shift in various local times. Chao and Luhr (2014) presented a description of the southern and northern MSNA in terms of solar tidal signatures focusing on 40°-60°geomagnetic latitude ranges, which is the region where the reversed diurnal variations of the electron density are strongest from the solar minimum years 2008 and 2009.…”

“…Recently, the tidal decomposition has been applied to TEC and/or electron density derived from inversion of TEC using radio occultation technique of FORMOSAT3/COS-MIC (F3/C), to quantify the components dominating local time and spatial variation in the WSA region (Chang et al 2015). Liu et al (2014) and Chang et al (2012) showed that the eastward drift of the three-dimensional F3/C electron density with HWM93 field-aligned winds agree with the eastward movements of the WSA.…”

Ionospheric Peaked Structures and Their Local Time, Seasonal, and Solar Activity Dependence Based on Global Ionosphere Maps

“…At 20:00 LT, the TEC enhancement appears in the region from 135°E to 90°W and from 40°S to 80°S. These peaks and dips in the higher geographic latitude region of the Southern Hemisphere correspond to the WSA, which appears mostly in local Summer (Burns et al, ; F. Y. Chang, Liu, Chang, et al, ; L. C. Chang, Liu, Miyoshi, et al, ; Chen et al, ; Chen et al, ; Jee et al, ; Liu et al, ; Penndorf, ). The WSA location in Figures and is similar to the WSA location observed by Jee et al ().…”

The Midlatitude Trough and the Plasmapause in the Nighttime Ionosphere Simultaneously Observed by DEMETER During 2006–2009

“…Figure displays in the Northern Hemisphere that the NT N e and NT T e departures are generally small over 0°E to 90°E geomagnetic (−60°E to 30°E geographic, approximately), where is coincident with one of the MSNA (midlatitude summer nighttime anomaly) areas during 2200 LT (Chang et al, ; Lin et al, ; Liu et al, ). In the Southern Hemisphere, departures of ST N e and ST T e are small over 30°E to 60°E geomagnetic (90°E to 0°E geographic), where it is coincident with the WSA (Weddell Sea anomaly) area during 2200 LT (Chang et al, ; Liu et al, ; Lin et al, ; Liu et al, ).…”