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 [RE] < 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. Plain Language Summary: The Earth's magnetosphere serves as a shield against extreme space weather conditions, including interplanetary coronal mass ejections. Understanding the magnetospheric dynamics during geomagnetic storms is critical for a reliable and accurate space weather prediction capability. This study provides a novel statistical analysis technique for investigating the magnetospheric closed magnetic flux content during different storm phases, using magnetic field data from a multitude of satellite missions. The technique considers critical information, such as the state of the magnetosphere before a geomagnetic storm. This multi‐mission analysis technique, though challenging due to orbital differences, provides a comprehensive view of the storm‐time magnetosphere. Our analysis suggests that the magnetosphere is non‐uniformly impacted by different geomagnetic storm phases, paving the path for more reliable storm prediction models. Key Points: Concurrent, multi‐probe observations help preserve magnetospheric time history for a more reliable space weather prediction capabilityMagnetic flux is substantially reduced in the nightside inner magnetosphere during all storm phases, relative to the quiet periodMagnetic flux changes between different storm phases are most significant in the nightside inner magnetosphere, asymmetric on the dayside [ABSTRACT FROM AUTHOR]