A fresh look at the intensity and impulsive strength of geomagnetic storms

Abstract

We notice an inconsistency in the geomagnetic storms having positive main phase onset (MPO >0 nT). The inconsistency makes the values of the storm indices (Dst and SymH) during the main phase and recovery phase significantly less than their actual values. We correct the inconsistency in 848 such storms (out of 1164 storms) during 1981-2019 by raising the 0-level of SymH to the MPO-level. The physically meaningful correction considers the full range of the main phase, increases the storm intensity (SymHMin) and impulsive strength (IpsSymH) by up to -149 nT and -139 nT, respectively, and seems important for all aspects of global space weather. For example, the corrected SymHMin changes the conventional storm identification and classification and corrected IpsSymH clearly identifies all 3 severe space weather events and 8 minor-system-damage space weather events from over 1100 normal space weather events.