Magnetospheric Time History in Storm‐Time Magnetic Flux Dynamics

Abstract

Magnetospheric magnetic flux dynamics is quantified in 29 geomagnetic storms between 2015 and 2019, using near‐equatorial Van Allen Probe, GOES, and Magnetospheric Multiscale (MMS) 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.

Magnetospheric Time‐History in Storm‐Time Magnetic Flux Dynamics: A Global Simulation Campaign

“…Similar findings have been reported by Akhavan‐Tafti, Atilaw, et al. (2023) using in‐situ measurements of 29 storm events, in particular for the main and recovery phases. On the contrary, the SSC phase result from Akhavan‐Tafti, Atilaw, et al.…”

“…The quiet period used by Akhavan‐Tafti, Atilaw, et al. (2023) is 30 hr on average. Whereas the average quiet period duration used for this study is 5 hr, which might not be sufficient to obtain the quiet time baseline of the magnetosphere.…”

“…The SYM-H index is used to classify the different storm phases, where the sudden increase in the SYM-H index (i.e., |SYM-H| ≥ 5 nT) marks the start of the SSC phase, the sharp decrease in the SYM-H index lasting for several hours (minimum of 3 hr used as a threshold for this study) marks the end of the SSC phase and the beginning of the main phase. The full description of the storm phase classification can be found in the methodology section of Akhavan-Tafti, Atilaw, et al (2023) paper. For this study, we have analyzed 15 out of the 29 events presented in Akhavan-Tafti, Atilaw, et al (2023), by focusing on the events where we have sufficient quiet period data from the simulation to use as a baseline when determining the relative flux change.…”

“…The full description of the storm phase classification can be found in the methodology section of Akhavan‐Tafti, Atilaw, et al. (2023) paper. For this study, we have analyzed 15 out of the 29 events presented in Akhavan‐Tafti, Atilaw, et al.…”

“…The full description of the storm phase classification can be found in the methodology section of Akhavan-Tafti, Atilaw, et al (2023) paper. For this study, we have analyzed 15 out of the 29 events presented in Akhavan-Tafti, Atilaw, et al (2023), by focusing on the events where we have sufficient quiet period data from the simulation to use as a baseline when determining the relative flux change. The average duration of the quiet, SSC, main and recovery phases are 5 hr, 7 hr, 12 hr and 18 hr, respectively.…”