Substorms and Solar Eclipses: A Mutual Information Based Study.

Coyle, S. E.; Baker, J. B. H.; Chakraborty, S.; Hartinger, M. D.; Freeman, M. P.; Clauer, C. R.; Xu, Z.; Weimer, D. R.

Solar eclipses present a rare glimpse into the impact of ionospheric electrodynamics on the magnetosphere independent of other well studied seasonal influences. Despite decades of study, we still do not have a complete description of the conditions for geomagnetic substorm onset. We present herein a mutual information based study of previously published substorm onsets and the past two decades of eclipses which indicates the likelihood of co‐occurrence is greater than random chance. A plausible interpretation for this relation suggests that the abrupt fluctuations in ionospheric conductivity during an eclipse may influence the magnetospheric preconditions of substorm initiation. While the mechanism remains unclear, this study presents strong evidence of a link between substorm onset and solar eclipses. Plain Language Summary: Geomagnetic substorms are a long‐studied phenomenon with significant potential for impact on human infrastructure and activities. Despite decades of research, a comprehensive description of what causes these violent eruptions of space plasma near earth has yet to be agreed upon. Although their evolution is well documented, the precise conditions required for substorms to manifest appear to be more complex than previously understood. We present evidence in this manuscript of a mutual dependence between solar eclipses and substorms, which suggests that changes to the upper atmosphere like those occurring during an eclipse may influence substorm development. Key Points: In a given 2 hr window between 2001 and 2021, a substorm occurs roughly 40% of the time, increasing to 67% during windows including an eclipseConditional Point‐wise Mutual Information analysis suggests the probability of eclipse‐substorm co‐occurrence is higher than random chanceThe mutual dependence between eclipses and substorms is likely the result of ionospheric conductivity feedback into the magnetosphere

MAGNETIC storms; SOLAR eclipses; ECLIPSES; UPPER atmosphere; SPACE plasmas; MAGNETOSPHERE; ELECTRODYNAMICS

Geophysical Research Letters, 2023, Vol 50, Issue 24, p1

0094-8276

Academic Journal

10.1029/2023GL106432