17:15 〜 19:15
[PEM13-P11] 地磁気変動から推定される巨大磁気嵐中の環状電流の時間空間変動
キーワード：環状電流、磁気嵐、地磁気変動
The spatiotemporal variations of the ring current during geomagnetic storms are crucial for understanding the magnetospheric current system and magnetospheric dynamics. Previous studies investigated the intensity of the partial ring current and its asymmetry in the magnetic local time (MLT) direction during geomagnetic storms. In this study, we further analyze the temporal evolution of the spatial extent of the partial ring current during the storm main and early recovery phases.
We use geomagnetic data from INTERMAGNET at geomagnetic low latitudes (|MLAT| = 10 - 30 deg.). The analysis focuses on events that occered on October 11, 2024, May 11, 2024, December 2, 2023, April 24, 2023, and March 18, 2015, with particular emphasis on the 2024 events. We remove the baseline and the diurnal Sq variations from geomagnetic data at 14 stations distributed globally in the MLT direction. We then analyze the time series of the MLT variations, which are binned as a function of UT with the time period of 3 h and MLT in steps of 2 h. This MLT-UT map is further processed with the harmonic fitting in the MLT direction.
The results showed that the ring current expands from the midnight (00 MLT) to the noon-to-dusk sector (12-18 MLT) and subsequently shifts toward the noon (12 MLT). This evolution likely corresponds to plasma convected from the midnight sector, drifting westward, and eventually reaching the dayside magnetopause. This study investigates the formation process of the equatorial partial ring current in detail. It also highlights the usefulness of ground-based observations in analyzing large-scale magnetospheric current systems and plasma dynamics.
We use geomagnetic data from INTERMAGNET at geomagnetic low latitudes (|MLAT| = 10 - 30 deg.). The analysis focuses on events that occered on October 11, 2024, May 11, 2024, December 2, 2023, April 24, 2023, and March 18, 2015, with particular emphasis on the 2024 events. We remove the baseline and the diurnal Sq variations from geomagnetic data at 14 stations distributed globally in the MLT direction. We then analyze the time series of the MLT variations, which are binned as a function of UT with the time period of 3 h and MLT in steps of 2 h. This MLT-UT map is further processed with the harmonic fitting in the MLT direction.
The results showed that the ring current expands from the midnight (00 MLT) to the noon-to-dusk sector (12-18 MLT) and subsequently shifts toward the noon (12 MLT). This evolution likely corresponds to plasma convected from the midnight sector, drifting westward, and eventually reaching the dayside magnetopause. This study investigates the formation process of the equatorial partial ring current in detail. It also highlights the usefulness of ground-based observations in analyzing large-scale magnetospheric current systems and plasma dynamics.