On the Sources, Coupling and Energetics During Supersubstorms of the Solar Cycle 24

Abstract

The geomagnetic storms are associated with substorms, however, isolated substorms are also known to occur through the magnetospheric processes without an immediate or explicit forcing from the sun (Liou et al., 2013;Nishida & Kamide, 1983;Vorobjev et al., 2016). Additionally, there may be cases when the magnetosphere is in presubstorm state and a change in the interplanetary parameters may eventually favor the generation of a substorm (Guo et al., 2012; Sandholt et al., 2014, and references therein).Substorms of varying magnitudes have been customarily identified by using the AL (auroral lower component) index along with the gross night side activity by using the AE (auroral electrojets) index. The denser SuperMAG network of magnetometers has made it possible to define a new pair of indices called SME (super magnetic electrojets) index and SML (lower component of SME) index (Newell & Gjerloev 2011a, 2011b) which can better identify the spatio-temporal occurrence of the substorms. Using the SML data, Tsurutani et al. ( 2015) have found that substorms can occur as extreme events and a threshold of SML < −2,500 nT has been used to declare it as supersubstorms (SSSs). Subsequently, Hajra et al. (2016) have analyzed more than 70 geomagnetic storms with a superposed epoch analysis and found that SSSs may not have a strong relationship with the associated geomagnetic storm and also that seasonal variations show ionospheric dominance during such events. The solar wind sources that drive the extreme substorm events have been studied by Hajra et al. (2016), Adhikari et al. (2017 and Despirak et al. (2019) and it has been shown that the SSSs are sourced majorly from magnetic clouds (MCs) and the interplanetary sheath fields. These studies have also reported that a majority of the SSSs occur during the initial or main phase of the geomagnetic storms. Nishimura et al. (2020) have highlighted the dominance of nightside drivers and magnetotail during the SSSs. They found enhancements in auroral brightening, TEC

Global Observations of the Short‐Term Disturbances in the Geomagnetic Field and Induced Currents During the Supersubstorms Events of Solar Cycle 24

“…The data set of the SML index (Newell & Gjerloev, 2011) is obtained from the website of the SuperMag (https://supermag.jhuapl.edu/indices/). It is noteworthy to mention that the durations of the supersubstorms are as taken as per the time-intervals mentioned in Hajra et al (2022). The global high-resolution geomagnetic observations are obtained from the latitudinal and longitudinal chains of magnetometers available at the INTERMAGNET website (https://www.intermagnet.org/data-donnee/download-eng.php) (see Love & Chulliat, 2013 for the description of the data set).…”

“…The variations in the AE and SML indices show the phases of the auroral perturbations during the supersubstorms, whereas the SYM-H index is added to signify the associated geomagnetic storm phases. The supersubstorm durations for these cases are provided by Hajra et al (2022) in a detailed manner and these durations are highlighted in all the results of the present study. A close inspection of the solar wind parameters shows that the global minima in the variations in the IMF-B y are found before or during the supersubstorms.…”

“…Different aspects of the supersubstorms have been reported in the literature such as the sources, occurrence characteristics, morphology, and the associated auroral evolution (Adhikari, Baruwal, & Chapagain, 2017;Adhikari, Dahal, & Chapagain, 2017;Despirak et al, 2019Despirak et al, , 2020Despirak et al, , 2021Hajra et al, 2016;Hajra and Tsurutani, 2018;Nishimura et al, 2020;Tsurutani et al, 2015). Recently, Hajra et al (2022) have reported a detailed analysis of the supersubstorms of solar cycle 24 including the originating solar wind structures, solar wind-magnetosphere-ionosphere coupling efficiencies, and the associated energy partitioning in the magnetosphere-ionosphere system. They have noted that the multiple hits by magnetic cloud structures have triggered the supersubstorms of the solar cycle 24 during the respective ongoing geomagnetic storms.…”

Universal Time Variations in the Magnetosphere and the Effect of CME Arrival Time: Analysis of the February 2022 Event that Led to the Loss of Starlink Satellites

“…For very quiet times particle precipitation seems to dominate magnetospheric energy deposition in the ionospherethermosphere system; however, for small storms, the Joule heating by the ionospheric E-region Pedersen currents associated with F-region convection (X. Zhang et al, 2005;Kalafatoglu et al, 2018) is slightly larger than that due to particle precipitation, and for large storms Joule heating is dominant (Wilson et al, 2006;Robinson & Zanetti, 2021;Hajra et al, 2022). To define the Joule heating input to the coupled thermosphere-ionosphere model, Dang et al (2022) employed the empirical convection and Joule heating model of Weimer (2005) which uses the prevailing solar wind and IMF conditions and assumes a steady-state response of the magnetosphere with only directly-driven energy deposition.…”

Universal Time Variations in the Magnetosphere and the Effect of CME Arrival Time: Analysis of the February 2022 Event that Led to the Loss of Starlink Satellites

“…For very quiet times particle precipitation seems to dominate magnetospheric energy deposition in the ionosphere-thermosphere system; however, for small storms, the Joule heating by the ionospheric E-region Pedersen currents associated with F-region convection (Kalafatoglu et al, 2018;X. Zhang et al, 2005) is slightly larger than that due to particle precipitation, and for large storms Joule heating is dominant (Hajra et al, 2022;Robinson & Zanetti, 2021;Wilson et al, 2006). To define the Joule heating input to the coupled thermosphere-ionosphere model, Dang et al (2022) employed the empirical convection and Joule heating model of Weimer (2005) which uses the prevailing solar wind and IMF conditions and assumes a steady-state response of the magnetosphere with only directly-driven energy deposition.…”