Abstract
The dynamics of ionospheric troughs during intense geomagnetic storms is considered in this paper. The study is based on electron density measurements at CHAMP satellite altitudes of 405–465 km in the period from 2000 to 2002. A detailed analysis of four storms with Kp from 5+ to 9− is presented. Three troughs were identified: sub-auroral, mid-latitude, and low-latitude. The sub-auroral trough is usually defined as the main ionospheric trough (MIT). The mid-latitude trough is observed equatorward of the MIT and is associated with the magnetospheric ring current; therefore, it is named the ring ionospheric trough (RIT). The RIT appears at the beginning of the storm recovery phase at geomagnetic latitudes of 40–45° GMLat (L = 1.75–2.0) and exists, for a long time, at the late stage of the recovery phase at latitudes of the residual ring current 50–55° GMLat (L ~ 2.5–3.0). The low-latitude trough (LLT) is discovered for the first time. It forms only during great storms at the latitudes of the internal radiation belt (IRB), 34–45° GMLat (L = 1.45–2.0). The LLT’s lowest latitude of 34° GMLat was recorded in the night sector (2–3 LT). The occurrence probability and position of the RIT and LLT depend on the hemisphere and longitude.
Highlights
Troughs during Severe GeomagneticIn [1,2], the extreme states of the night sector of the magnetosphere were considered.These were the minimum latitudes (Lmin -shell) of the auroral oval of precipitation, main ionospheric trough, plasmapause, and SAR-arc, depending on the maximum values of the geomagnetic activity indices Kp and Dst
The purpose of this paper is to continue the study of the dynamics of the ionospheric troughs during strong geomagnetic storms and to carry out a statistical analysis of the main ionospheric trough (MIT), ring ionospheric trough (RIT), and low-latitude trough (LLT) position dependence on the Kp-index, in comparison with the position of other structures of the night ionosphere
All events in this paper are considered in terms of the Kp-index, as variations in the MIT position are related to Kp variations, according to a model presented earlier [14]
Summary
In [1,2], the extreme states of the night sector of the magnetosphere were considered These were the minimum latitudes (Lmin -shell) of the auroral oval of precipitation, main ionospheric trough, plasmapause, and SAR-arc (stable auroral red arc), depending on the maximum values of the geomagnetic activity indices Kp and Dst. These were the minimum latitudes (Lmin -shell) of the auroral oval of precipitation, main ionospheric trough, plasmapause, and SAR-arc (stable auroral red arc), depending on the maximum values of the geomagnetic activity indices Kp and Dst The observation data, both statistical and for several giant storms with Кр= 9 and Dst up to −430 nT, were used. As the main ionospheric trough (MIT) is usually located 2–5◦ equatorward of the auroral oval, it can reach latitudes of 43–46◦ GMLat (L = 1.9–2.1) [4].
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