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The Complex Space Weather Events of September 2017
  • Rajkumar Hajra,
  • Bruce, T. Tsurutani,
  • Gurbax, S. Lakhina
Rajkumar Hajra
National Atmospheric Research Laboratory

Corresponding Author:[email protected]

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Bruce, T. Tsurutani
Jet Propulsion Laboratory, California Institute of Technology
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Gurbax, S. Lakhina
Indian Institute of Geomagnetism
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The complex magnetospheric and ionospheric events during September 2017 are studied. There were 4 X-class, 27 M-class and numerous C-class flares related to ~68 coronal mass ejections (CMEs), 4 of which were halo CMEs. Of the 4 halo CMEs, only 3 reached the Earth. A fast interplanetary-CME (ICME) created an upstream sheath that caused an intense magnetic storm (SYM-H peak = -146 nT). This was followed by another intense storm (SYM-H peak = -115 nT) caused by the magnetic cloud (MC) portion of the ICME. Two moderate storms (with SYM-H peaks of -65 nT and -74 nT) were caused by a sheath associated with another halo CME and a corotating interaction region (CIR), respectively. The solar wind high-speed streams (HSSs) led to continuous substorm and convection events but no magnetic storms. Fast forward shocks (FSs) and reverse waves (RWs) associated with the fast CMEs and CIRs, and heliospheric current sheet/heliospheric plasma sheet encounters were detected. The FSs and RWs caused positive and negative sudden impulses, respectively. Half of the FSs triggered substorm onsets and the RWs caused substorm recovery phases. While the FSs led to magnetospheric relativistic electron decreases, electron accelerations were associated with the MC and the HSSs. During main phases of the intense storms, two supersubstorms (SSSs) were detected, one triggered by a FS and the other by a non-shock ram pressure pulse. The SSSs caused major geomagnetically induced currents. CME propagation codes were tested with errors in arrival times ranging from ~24 min to > 35 h.
06 Aug 2020Published in The Astrophysical Journal volume 899 issue 1 on pages 3. 10.3847/1538-4357/aba2c5