Similarities and differences between heliosphere-geosphere couplings associated with the short and long lived subauroral ionospheric storms: November 2004, F2 region, North East Asia

We analysed ground and in situ data collected on 9-10 November 2004 during the first day of the long-lived ionospheric storm which consequences were observed in the ionosphere till 13 November and compared the results with those obtained from the short-lived 7-8 November ionospheric storm study. During the first day of each storm we observed a positive nocturnal phase associated with a movement of the plasma sheet inner edge towards the Earth and westward auroral electrojet amplification. In both cases morning-midday negative phases of the storms evolved over the north-west electrojet in the compressed magnetosphere. The short-lived negative phase of 7-8 November storm evolved with the south-west interplanetary magnetic field (IMF), solar wind velocity VSW about 600 km/s and was associated with irregular geomagnetic pulsations. The long-lived negative phase of 9-13 November storm started with the north-west IMF, solar wind velocity about 800 km/s, and was associated with continuous Pc5 pulsations. We suppose that the high-latitude reconnection and Pc5 provided an additional energy input to the subauroral ionosphere and thereby contributed to formation of the long-lived neutral composition disturbance zone

Ionospheric disturbances over East Asia during intense December magnetic storms of 2006 and 2015: similarities and differences

Using data from ionosondes, located in East Asia, and total electron content maps, we have made a comparative analysis of ionospheric disturbances associated with the intense geomagnetic storms of December 14–16, 2006 and December 19–22, 2015. These storms had almost equal peak intensities (Dstmin=–162 and –155 nT), but different durations of the main phases (2.5 and 19 hr). At the beginning of both the storms, the region under study was located in the vicinity of the midnight meridian. Ionospheric responses to magnetic storms differed in: i) an increase in the F2-layer critical frequency at subauroral latitudes, caused by an increase in auroral precipitation, during the initial phase of the former storm and the absence of this effect in the latter; (ii) a sharp drop in the critical frequency in the evening hours of the main phase of the latter storm, caused by a shift of the main ionospheric trough to lower latitudes, and the absence of this effect during the former storm; (iii) generation of a short-term positive disturbance observed at subauroral latitudes only in the early recovery phase of the former storm after the negative ionospheric disturbance. During both the storms at middle latitudes there were positive disturbances and wave-like fluctuations of the critical frequency which increased in the vicinity of the dawn meridian. The main causes of the differences between the ionospheric storms are shown to be the differences between the initial conditions of the magnetosphere–ionosphere system and durations of the main phases of magnetic storms

Backscattering dynamics during intense geomagnetic storm as deduced from Yekaterinburg radar data: March 17–22, 2015

This paper examines the spatio-temporal dynamics of backscattering signals during St. Patrick’s Day two-step intense geomagnetic storm from the Yekaterinburg Coherent Radar (YeKB radar) data. It is found that a number of ground backscattering signals increased during the initial phase of the storm and decreased during the second step of its main phase and the first two days of its recovery phase. Changes in ionospheric backscattering signals started at the beginning of the main phase. During the first step, there was a six-hour sequence of ionospheric backscattering signals (BSi signals) the range of which decreased while the storm was in progress. During the last 5 hours of the main phase and the first 3 hours of the recovery phase, the YeKB radar observed only signals scattering in the E region of the ionosphere. We conduct a complex analysis of data from the YeKB radar, ground-based ionospheric, riometric, and magnetic stations located within the radar field of view. The analysis shows that the observed backscattering dynamics was caused by the magnetosphere compression, expansion of convection cells, impact ionization, and changes in atmospheric composition during the initial storm phase, first and second steps of the main phase, and the recovery phase respectively