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<p>This research examines the variations of the relativistic electron flux (REF) with E &gt; 0.8&#xa0;MeV and &gt; 2&#xa0;MeV at geostationary orbit (GEO) and in outer radiation belts (ORB) selected events of high-intensity long-duration continuous AE activity (HILDCAA) during 2015 to 2017. We have utilized the solar wind plasma data and geomagnetic storm indices, source and seed electron flux, chorus wave spectrograms, and ULF indices. We found strong linear correlation between the maximum of AE (AL) and max REF, and between the peaks solar wind speed (V<sub>max</sub>) and max Log REF. The E &gt; 0.8&#xa0;MeV REF increases before the E &gt; 2.0&#xa0;MeV REF. Then they concurrently changed with the increasing rate of the E &gt; 2.0&#xa0;MeV REF is faster than that of the E &gt; 0.8&#xa0;MeV REF. The Alfvénicity (i.e., the extent to which fluctuations follow the Alfvén wave characteristics), with the southward interplanetary magnetic field of the Alfvén waves is essential for the substorm occurrence. The REF enhancements at GEO are categorized into nominal, high, and very high levels. The conditions of very high REF are 1690 ≤ AE<sub>max</sub> ≤ 2178 nT and 742 ≤ V<sub>max</sub> ≤ 860&#xa0;km/s. The large ULF waves are found in the high and very high REF and often appear in the high-Alfvénic events. The Chorus wave activity persists in conjunction with the injection of source and seed electrons. Nominal REF occurs in the moderate ULF and the highest REF was around L = 4–5 without loss of REF in the ORB. The prominent Chorus and ULF waves recurrently appear in some consecutive HILDCAA events that sequentially and synergistically enhance the REF to very high levels. Near L = 4, the REF was locally enhanced by Chorus wave throughout the HILDCAA and recovery phase. The consecutive recurrent Chorus relates to the loss of REF in the range of L = 4–6. Events with no clear Chorus in the ORB can possess high and very high REF at GEO and the loss of REF is at L = 4–5 during the Equinoctial times. Moreover, REF shows semiannual variation, with maxima fluxes near the equinoxes.</p>

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Contribution of Alfvén, Chorus, and ULF waves to high-energy electron flux at geostationary orbit in HILDCAA events during 2015 to 2017

  • 期刊论文

  • 发表日期：

    2025年11月24日

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  • Thana Yeeram

摘要

This research examines the variations of the relativistic electron flux (REF) with E > 0.8 MeV and > 2 MeV at geostationary orbit (GEO) and in outer radiation belts (ORB) selected events of high-intensity long-duration continuous AE activity (HILDCAA) during 2015 to 2017. We have utilized the solar wind plasma data and geomagnetic storm indices, source and seed electron flux, chorus wave spectrograms, and ULF indices. We found strong linear correlation between the maximum of AE (AL) and max REF, and between the peaks solar wind speed (Vmax) and max Log REF. The E > 0.8 MeV REF increases before the E > 2.0 MeV REF. Then they concurrently changed with the increasing rate of the E > 2.0 MeV REF is faster than that of the E > 0.8 MeV REF. The Alfvénicity (i.e., the extent to which fluctuations follow the Alfvén wave characteristics), with the southward interplanetary magnetic field of the Alfvén waves is essential for the substorm occurrence. The REF enhancements at GEO are categorized into nominal, high, and very high levels. The conditions of very high REF are 1690 ≤ AEmax ≤ 2178 nT and 742 ≤ Vmax ≤ 860 km/s. The large ULF waves are found in the high and very high REF and often appear in the high-Alfvénic events. The Chorus wave activity persists in conjunction with the injection of source and seed electrons. Nominal REF occurs in the moderate ULF and the highest REF was around L = 4–5 without loss of REF in the ORB. The prominent Chorus and ULF waves recurrently appear in some consecutive HILDCAA events that sequentially and synergistically enhance the REF to very high levels. Near L = 4, the REF was locally enhanced by Chorus wave throughout the HILDCAA and recovery phase. The consecutive recurrent Chorus relates to the loss of REF in the range of L = 4–6. Events with no clear Chorus in the ORB can possess high and very high REF at GEO and the loss of REF is at L = 4–5 during the Equinoctial times. Moreover, REF shows semiannual variation, with maxima fluxes near the equinoxes.