Magnetospheric Time History in Storm-Time Magnetic Flux Dynamics

Magnetospheric magnetic flux dynamics is quantified in 29 geomagnetic storms between 2015 and 2019, using near-equatorial Van Allen Probe, GOES, and Magnetospheric Multiscale satellites. For the first time, concurrent, multi-probe observations are utilized to preserve magnetospheric time history, defined as the state of the magnetosphere leading up to an observation. It is revealed that, relative to pre-storm conditions, (a) during the storm sudden commencement (SSC), magnetic flux uniformly increases ΔΨ = +15% throughout the magnetosphere, except in the nightside inner magnetosphere where ΔΨ = −30%, and (b) during storm main and recovery phases, ΔΨ = −30% and −15%, respectively, in the nightside magnetosphere, at radial distances 5 ≤ r [R_E] < 8. It is found that a symmetric ring current is likely formed in the nightside, early in the storm process (localized during SSC), which then broadens during the main phase, before weakening during the recovery phase. The current system on the dayside shows a distinct dawn-dusk asymmetry.