Similarity and differences in morphology and mechanisms of the <i>fo</i>F2 and TEC disturbances during the geomagnetic storms on 26–30 September 2011

Abstract

Abstract. This study presents an analysis of the groundbased observations and model simulations of ionospheric electron density disturbances at three longitudinal sectors (eastern European, Siberian and American) during geomagnetic storms that occurred on 26-30 September 2011. We use the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) to reveal the main mechanisms influencing the storm-time behavior of the total electron content (TEC) and the ionospheric F2 peak critical frequency (foF2) during different phases of geomagnetic storms. During the storm's main phase the long-lasting positive disturbances in TEC and foF2 at sunlit mid-latitudes are mainly explained by the storm-time equatorward neutral wind. The effects of eastward electric field can only explain the positive ionospheric storm in the first few hours of the initial storm phase. During the main phase the ionosphere was more changeable than the plasmasphere. The positive disturbances in the electron content at the plasmaspheric heights (800-20 000 km) at high latitudes can appear simultaneously with the negative disturbances in TEC and foF2. The daytime positive disturbances in foF2 and TEC occurred at middle and low latitudes and at the Equator due to n(O) / n(N 2 ) enhancement during later stage of the main phase and during the recovery phase of the geomagnetic storm. The plasma tube diffusional depletion and negative disturbances in electron and neutral temperature were the main formation mechanisms of the simultaneous formation of the positive disturbances in foF2 and negative disturbances in TEC at low latitudes during the storm's recovery phase.

After-effects of geomagnetic storms: statistical analysis and theoretical explanation

“…Thus, the problem of theoretical justification of the fact that the most favorable conditions for positive after-effects of geomagnetic storms exist in spring is still unsolved. It should again be noted that the previous model calculations of ionospheric responses to magnetic storms Klimenko et al, 2017Klimenko et al, , 2018 have shown that a positive after-storm effect can be observed both in fall and in spring.…”

“…The previous results Klimenko et al, 2017Klimenko et al, , 2018 offered no insight into the question of whether the after-storm effects characterize the September 26, 2011 and March 17, 2015 geomagnetic storms or they are typical of all geomagnetic storms. To answer this question, we have developed a special method of statistical analysis of ionospheric responses to geomagnetic storms, which is based on Irkutsk (52° N, 104° E) and Kaliningrad (54° N, 20° E) ionosonde data.…”

“…The behavior of the ionosphere at the late recovery phase and after a geomagnetic storm has practically not been investigated. Model calculations and observations of ionospheric effects of geomagnetic storms on Septem-ber 26, 2011 (Dst=-118 nT) and March 17, 2015 (Dst=-223 nT) have, however, shown the presence of sufficiently strong positive electron density disturbances observed during the daytime on the 3-5th day after the beginning of the geomagnetic storm recovery phase Klimenko et al, 2017Klimenko et al, , 2018. Hereafter, the daytime ionospheric effects observed on the 3-5th day after the beginning of the recovery phase are called after-storm effects.…”

“…Calculations of upper atmosphere parameters Klimenko et al, 2017Klimenko et al, , 2018, made using the Global Self-Consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) [Namgaladze et al, 1990;Klimenko et al, 2006;Korenkov et al, 1998], have shown that the main cause of positive after-storm effects is an increase in the ratio of atomic oxygen to molecular nitrogen n(O)/n(N 2 ). This result was unexpected since the well-known effect in the geomagnetic storm recovery phase is an opposite effecta decrease in n(O)/n(N 2 ), hence a negative electron density disturbance [Prölss, 1995].…”

Interhemispheric Asymmetry in Response of Low‐Latitude Ionosphere to Perturbation Electric Fields in the Main Phase of Geomagnetic Storms

“…It is found that the previous studies showcased the hemispheric asymmetry in ionospheric responses irrespective of daytime or nighttime and mostly the large scale spatiotemporal features up to the recovery phase have been discussed that show all kinds of effects including PPEF, TADs, and composition changes and disturbance dynamo de Abreu et al, 2010;Klimenko et al, 2017;Luo et al, 2016;Yao et al, 2016;Yiğit et al, 2016;Yue et al, 2016). It is found that the previous studies showcased the hemispheric asymmetry in ionospheric responses irrespective of daytime or nighttime and mostly the large scale spatiotemporal features up to the recovery phase have been discussed that show all kinds of effects including PPEF, TADs, and composition changes and disturbance dynamo de Abreu et al, 2010;Klimenko et al, 2017;Luo et al, 2016;Yao et al, 2016;Yiğit et al, 2016;Yue et al, 2016).…”