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

• Published in: Geoscience letters Vol. 11; no. 1; pp. 22 - 9
• Main Authors: Manu, V., Balan, N., Ebihara, Y., Zhang, Qing-He, Xing, Zan-Yang
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.12.2024; Springer Nature B.V; SpringerOpen
• Subjects: Atmospheric Sciences; Biogeosciences; Earth and Environmental Science; Earth Sciences; Fluctuations; Geomagnetic field; Geomagnetic storms; Geomagnetism; Geophysics/Geodesy; Magnetic storms; Oceanography; Planetology; Positive MPO; Research Letter; Space weather; Storm intensity and impulsive strength; Storms; Weather; Storm intensity and impulsive strength; Geomagnetic storms; Positive MPO
• ISSN: 2196-4092; 2196-4092
• DOI: 10.1186/s40562-024-00337-7

We notice that the important early decreasing part of the main phase (MP) from the positive main phase onset (MPO) to 0-level of Dst and SymH indices is missed in the treatment of the main phase (MP) of geomagnetic storms. We correct this inconsistency in 848 storms having positive MPO (out of 1164 storms) in SymH during 1981–2019 by raising the 0-level of SymH to the MPO-level. The correction considers the full range of the main phase, increases the corrected (revised) storm intensity (SymHMin*) and impulsive strength (IpsSymH*) by up to − 149 nT and − 134 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 (SvSW) events from over 1100 normal space weather (NSW) events with a separation of 52 nT; it also identifies all 8 minor-system-damage space weather (MSW) events from the NSW events. Plain Language Summary Large fluctuations occur in the global geomagnetic field during space weather events. The fluctuations at low latitudes are referred as geomagnetic storms. The Dst and SymH indices have been used for studying the storms and other aspects of global space weather. However, we notice that the Dst and SymH values during the main phase and recovery phase of the storms having positive main phase onset (MPO > 0 nT) are significantly less than their actual values. We correct this inconsistency in 848 such storms (out of 1164 storms) in SymH during 1981-2019 by raising the 0-level of SymH to the MPO-level. The corrected/revised storm intensity (SymHMin*) and impulsive strength (IpsSymH*) increase by up to − 149 and − 134 nT. The correction seems important for studying all aspects global space weather. For example, the correction identifies the storms corresponding to severe space weather causing power outage and/or telecommunication failure from those corresponding to normal space weather. Key points We correct an inconsistency in the SymH values during the MP and RP of the 848 storms having positive MPO during 1981–2019. The corrected values of SymHMin* and IpsSymH* increase by up to − 149 nT and − 134 nT compared to their uncorrected values. The correction changes the storm identification and clearly identifies all 3 SvSW and 8 MSW events from over 1100 NSW events.