Ionospheric response to the March 17, 2015 geomagnetic storm has been investigated using simulations of the Global Self-consistent Model of the Thermosphere, Ionosphere, Protonosphere (GSM TIP) [Dmitriev et al., 2017; Klimenko et al., 2018]. GSM TIP demonstrates results that do not contradict experimental data. This paper deals with GSM TIP simulated disturbances in the Total Electron Content (TEC) at different longitudes and zonal averages on March 17–23, 2015. At all longitudes, we can observe the existence of a band of TEC positive disturbances, located over the geomagnetic equator, and the formation of an after-storm ionospheric effect that appeared as positive TEC disturbances at midlatitude 3–5 days after the geomagnetic storm main phase. We have analyzed the dependence of disturbances of the thermosphere-ionosphere system (total electron content, n(N2), n(O), zonal electric field, meridional component of the thermospheric wind at a height of 300 km, and electron temperature at a height of 1000 km), calculated by GSM TIP from variations in the geomagnetic activity index AE. The analysis is based on Pearson’s correlation coefficients, presented as maps of the dependence of the correlation coefficient on UT and latitude for selected longitudes and for zonal averaged values. The results suggest that at high latitudes of the Northern and Southern hemispheres the correlation coefficient of TEC disturbances and AE variations is close to 1 at all longitudes in the period from 12 UT to 23 UT. From 9 UT to 12 UT, the minimum value of the correlation coefficient is observed at all latitudes and longitudes. The time intervals of the correlation values are associated with the features of a particular geomagnetic storm, for which, for example, the interval from 12 UT to 23 UT on March 17, 2015 corresponds to the geomagnetic storm main phase. We discuss possible mechanisms for the formation of such a relationship between simulated TEC disturbances and the AE index.

The paper studies statistical patterns of regional electron content responses to geomagnetic events at high, middle, and equatorial latitudes. The regional electron content is the total electron content averaged over all longitudes in a given latitudinal zone. The statistical analysis includes the following: 1) identification of geomagnetic events based on the AE index and calculation of “reference” geomagnetic storms; 2) calculation of the regional electron content (REC) for five latitudinal zones (equatorial zone, mid-latitude zones of the Northern and Southern hemispheres, and high-latitude zones of the Northern and Southern hemispheres); 3) calculation of REC disturbances (ΔREC), which are relative (percentage) deviations of the observed values, from the 27-day running mean of REC and 4) obtaining the “reference” ionospheric response in the form of the dynamics of average ΔREC, obtained by the superposed epoch method. The superposed epoch method is implemented with the hourly resolution and key moments corresponding to the AE index maximum. Compared with our previous statistical analysis, implemented with daily resolution based on geomagnetic storm identification by the Dst index, the new method leads to a significant increase in the amplitude and the time-focusing of the response. The seasonal behavior of ionospheric responses was analyzed for correspondence to the thermospheric storm concept. The responses of the equatorial and mid-latitude zones of the Southern Hemisphere fit the thermospheric storm concept. In the mid-latitude zone of the Northern Hemisphere, there are a number of exceptions. The responses of the high-latitude zone show the need to take into account the mechanisms behind the formation of positive disturbances, which are absent in the thermospheric storm concept.

The Global Self-Consistent Model of the Thermosphere, Ionosphere, and Protonosphere (GSM TIP) was used earlier to interpret ionospheric effects of the March 2015 geomagnetic storm. Positive aftereffects were identified and analyzed. Subsequent analysis of results from numerical modeling showed that positive aftereffects take different forms in different longitudinal sectors. This work presents results from studying the dependence of disturbances in the parameters of the upper atmosphere on the time (UT) of the start of a geomagnetic storm. It is shown that differences between mid-latitude effects during the main phase of a storm in N_mF2 and in storms with different starting times are due to differences in disturbances of the wind and the composition of the thermosphere. These differences become apparent 12 h after the start of a geomagnetic storm. The time at which mid-latitude aftereffects start to form, their amplitude, and their latitudinal extent depend on the time (UT) a geomagnetic storm starts.

The paper studies statistical patterns of regional electron content responses to geomagnetic events at high, middle, and equatorial latitudes. The regional electron content is the total electron content averaged over all longitudes in a given latitudinal zone. The statistical analysis includes the following: 1) identification of geomagnetic events based on the AE index and calculation of “reference” geomagnetic storms; 2) calculation of the regional electron content (REC) for five latitudinal zones (equatorial zone, mid-latitude zones of the Northern and Southern hemispheres, and high-latitude zones of the Northern and Southern hemispheres); 3) calculation of REC disturbances (ΔREC), which are relative (percentage) deviations of the observed values, from the 27-day running mean of REC and 4) obtaining the “reference” ionospheric response in the form of the dynamics of average ΔREC, obtained by the superposed epoch method. The superposed epoch method is implemented with the hourly resolution and key moments corresponding to the AE index maximum. Compared with our previous statistical analysis, implemented with daily resolution based on geomagnetic storm identification by the Dst index, the new method leads to a significant increase in the amplitude and the time-focusing of the response. The seasonal behavior of ionospheric responses was analyzed for correspondence to the thermospheric storm concept. The responses of the equatorial and mid-latitude zones of the Southern Hemisphere fit the thermospheric storm concept. In the mid-latitude zone of the Northern Hemisphere, there are a number of exceptions. The responses of the high-latitude zone show the need to take into account the mechanisms behind the formation of positive disturbances, which are absent in the thermospheric storm concept

This study investigates subauroral phenomena during the main phase of the 10 May 2024 geomagnetic storm using a combination of ground-based observations from the WD IZMIRAN observatory (magnetometer, ionosonde, and all-sky imager) and Global Self-consistent Model of the Thermosphere, Ionosphere, Protonosphere (GSM TIP) simulations. During 18:00–20:00 UT, we identified the simultaneous occurrence of ionospheric signatures of Polarization Jets (PJ)/Sub-Auroral Ion Drifts (SAID) and Strong Thermal Emission Velocity Enhancement (STEVE) over Kaliningrad, consistent with previously reported PJ/SAID identification from DMSP drift velocity measurements. This identification is supported by: (1) characteristic purple emissions (clearly visible in all three channels) moving rapidly westward; (2) U-shaped structures in ionogram sequences; (3) the reproduction of supersonic westward plasma drifts within a narrow latitudinal band by the first-principles model; and (4) observed and simulated significant Ne depletion. The estimated ion drift velocity from all-sky imaging (assuming an emission altitude of 200 km) is consistent with GSM TIP simulations, which predicted PJ/SAID velocities of ~750 m/s driven by a latitudinally narrow (~3°) but longitudinally extended (>50°) poleward electric field (40 mV/m). Simulations reveal that this PJ/SAID phenomenon causes a reversal of the zonal thermospheric wind at 250 km and induces Ne disturbances across the 200–700 km altitude range. The electron temperature enhancement (up to 1500 K) exhibits a “falling drop” shape, peaking at 350 km, while ion heating exceeds 150 K. The neutral temperature shows a dual response: frictional heating at 120–160 km and localized cooling at 175–250 km due to drop in electron density. Additionally, an increase in atomic oxygen concentration was predicted within the 90–200 km range across the PJ/SAID longitudinal sector.