Magnetospheric Observations of Dawnside Storm-time Wedge Current Systems

Geomagnetic storms are characterized by changes in the horizontal component of Earth's magnetic field corresponding to an increase in the strength of the ring current. Recently, Ohtani (2021) performed a statistical study using SuperMAG data to reveal a persistent feature of many storms they analyzed. Namely, they found that the low latitude ground magnetic field depression is dawn-dusk asymmetric in a way that they interpreted as a dawnside wedge current system closing partially through the dawnside westward auroral electrojet. Furthermore, rather than the partial ring current contribution, this dawnside wedge current adds to the greater magnetic depression at Earth's duskside and dawn-dusk asymmetry during magnetic storms.

This auroral wedge current system can be examined by using a combination of ground-based instruments (e.g., THEMIS ASI, REGO) and satellite data. In this work, we examine magnetometer data from the GOES, MMS, RBSP, and THEMIS satellites in parallel with ground-based auroral data from the REGO array to characterize this storm-time M-I coupling system. Since it is likely that this current system is a result of a magnetotail process, we also hope to gain a better understanding of storm-time magnetotail dynamics.