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Abstract:
Using the plasma instruments (LEPi, LEPe, MEPi and MEPe) onboard the Arase satellite, we can comprehensively investigate the fluxes of electrons and ions with different energies. Also, the in-situ electron density can be estimated by using the upper hybrid resonance frequencies detected from the plasma wave spectrum. The geomagnetic storm that commenced on 8 September 2017 has a Dst minimum of -147nT and appears to be a medium-sized magnetic storm at first glance, but it is known that it was a peculiar magnetic storm in various ways. For example, it is an extreme erosion of the plasmasphere to around L=1.5, and a strong SAPS generation. Our previous research suggested that this extreme erosion of the plasmasphere was the result of a convective electric field that continued to penetrate into the magnetic equatorial region for more than 6 hours, however, the reason for the continuation of the convection field was unclear. We therefore compare the evolution of ring current particles during this peculiar magnetic storm to the magnetic storm which commenced on 25 August 2018, which has a similar Dst minimum (-175nT) and erode plasmasphere to around L=2.5.
