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Interplanetary electric fields for extreme magnetic storms

Jeffrey J. Love·E. Joshua Rigler·Ian G. Richardson·Kalevi Mursula
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Abstract

Using a list of sudden-commencement storms, the ring-current index, and 1-h near-Earth solar-wind measurements from solar cycles 20–25, we develop extreme-value statistical models relating storm intensity 𝐷 =max⁡{−𝐷⁢𝑠⁢𝑡} to the storm main-phase maximum duskward interplanetary electric field 𝐸 . The conditional relationship 𝐷|𝐸 is demonstrably sublinear—linear models are confidently rejected—indicating saturation of magnetospheric response under extreme solar-wind forcing. An event like that of July 2012 ( 𝐸 =69.6 mV/m), if Earth-directed, would be associated with a median storm intensity of 𝐷 =49⁢5 648 378 nT. Storms comparable to March 1989 ( 𝐷 =594 nT) correspond to electric fields of 𝐸 =5⁢4 76 39 mV/m, while Carrington-class storms ( 𝐷 =964 nT) correspond to 𝐸 =9⁢5 133 68 mV/m—substantially lower than several previous estimates. These results indicate that solar-wind conditions capable of driving extremely intense magnetic storms are less exceptional, and potentially more frequent, than previously thought.

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Jeffrey J. Love, E. Joshua Rigler, Ian G. Richardson, Kalevi Mursula. 2026-07-07. Interplanetary electric fields for extreme magnetic storms. https://doi.org/10.1029/2026gl122391

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