Distinctive plasma density features of the topside ionosphere and their electrodynamics investigated during southern winter

This study utilizes a novel technique to map the Defense Meteorological Satellite Program (DMSP) data across the two hemispheres to learn about the morphology and plasma composition of the topside ionosphere, and the underlying ionospheric dynamics. In the southern winter hemisphere, the regional maps tracked a heavy-ion (Ni-O+) trough,aurora zone, polar hole, and large plasma density depletion. The latter appeared in the region of the South Atlantic Magnetic Anomaly (SAMA). The electron temperature (Te) map detected the thermal characteristics of these features, while the plasma drifts and flux maps tracked their dynamics. Results show that there were special electrodynamic effects in the SAMA region due to the low magnetic field and high conductivity. These increased the vertical downward (VZ) and the westward (VY) drifts. Independently, the VZ and VY maps registered the affected area that was depleted in heavy ions and rich in light ions. Some field-aligned profiles tracked the impact of these SAMA effects on the heavy-ion trough, which was a stagnation trough and appeared markedly differently at different longitudes. At trough latitudes ((56 ± 4)S (geomagnetic) when Dstav = 0 nT), the elevated electron temperatures forming a Te peak indicated subauroral heating effects. A statistical study modeled the magnetic activity dependence of the Te peak’s magnitude and location and revealed their linear correlation with the activity level. Statistically, the Te peak increased [10.226 ± 1.355]K and moved equatorward [0.051 ± 0.009] (geomagnetic) per 1 nT decrease in the averaged Dst index. Per 1 nT increase in the averaged AE index, its magnitude increased [1.315 ± 0.444]K and the equatorward movement was [0.014 ± 0.003]

Investigating the relationships among the South Atlantic Magnetic Anomaly, southern nighttime midlatitude trough, and nighttime Weddell Sea Anomaly during southern summer

[i] This study utilized the multi-instrument data of the Defense Meteorological Satellite Program to investigate the evening/nighttime topside ionosphere during the 1996/1997 southern summer. A series of regional surface maps were constructed and permitted the tracking of the topside ionosphere's plasma density features, plasma composition, thermal structures, and vertical and horizontal plasma flows. These maps tracked a complete nighttime Weddell Sea Anomaly (WSA) and strong horizontal plasma flows that registered the high-conductivity regions of the South Atlantic Magnetic Anomaly (SAMA). These regions developed over the southeastern Pacific, just equatorward of the WSA, and over the South Atlantic. A heavy-ion stagnation trough developed poleward of the SAMA affected regions. Thus, the trough appeared on the WSA's equatorward side. During periods of increasing magnetic activity, the plasmapause was the WSA's poleward boundary. A statistical study modeled the trough's magnetic activity dependence and revealed a strong east-west hemispherical difference that was due to the SAMA effects. When the AE6 was 0 nT, the trough appeared at (57.49 ± 2.82)°S (geomagnetic) over the southwestern hemisphere. Owing to the SAMA's special electrodynamic effects, the trough developed at lower latitudes, (42.39 ± 3.04)°S, over the southeastern hemisphere. Meanwhile, the plasmapause occurred at ̃(62.5 ± 4)°S, and the WSA's peak appeared at ̃(56.2 ± 4)°S. Hence, there was a ̃20° (lat) separation between the trough and the plasmapause over the southeastern hemisphere. Between 210°E and 330°E (geographic), the WSA filled this gap. With increasing magnetic activity, the trough in the SAMA affected regions moved poleward at a rate of (0.0157 ± 0.004)°S/nT. Elsewhere, it had a (0.0196 ± 0.002)°S/nT equatorward movement

Registration of VLF-sferics at the von-Neumayer Station

A VLF-sferics-analyzer was operating at the German antarctic station von-Neumayer from January to July 1983. This analyzer registrated far distant lightning events in the frequency range between 5 and 9kHz. Assuming the location of these sources to be known, the propagation characteristics of the atmospheric wave guide between the earth and the ionosphere can be derived along the propagation path. The method of measurement is described. The data of June 1983 are evaluated and the distances of the sources are determined from a comparison with rain fall records during the same month and, in addition, from sferics registrations obtained at a second station in Pretoria, South Africa. The main result is that the ionospheric D layer along the propagation paths from the east coast of South America to the von-Neumayer station and from South Africa to the von-Neumayer station do not show a significant daily variation. The virtual ionospheric reflection height is about 82km for VLF waves between 5 and 9kHz during June. This corresponds to night time conditions at northern mid-latitudes in winter