A Comprehensive Classification of Geomagnetic storms
Asma^a A. Hamied and Khalid A. Hadi

Department of Astronomy and Space, College of Science, University of Baghdad, Baghdad, Iraq.

Abstract

Geomagnetic storms are considered a global disturbance in Earth^s magnetosphere resulting from many interactions with solar plasma. Despite the significance of this topic, previous studies have remained limited to analyzing individual indices or specific types of storms. This study addresses a fundamental knowledge gap by presenting a comprehensive statistical analysis and classification of geomagnetic storms during Solar Cycle 24, based on three key indices (Dst, ap, and AP). The scientific significance of this work resides in the presenting of a ^unified classification table,^ a novel framework that consolidates and harmonizes the diverse classification criteria of the three examined indices into a singular standard, thus providing a unified comprehensive classification and analysis of geomagnetic storms. The classification results derived from the proposed criteria (table) revealed that the total number of geomagnetic storms according to the Dst index was 859: 577 were weak, 247 were moderate, 34 were strong, 1 was severe, and no great storms were recorded. Furthermore, the outcomes revealed that the strongest storm occurred on 17 March 2015, with a Dst value of -234 nT, which was classified as a severe storm. While the findings showed that relying on the ap-index, 4017 storms were recorded: 826 were very quiet, 1169 were quiet, 1045 were unsettled, 595 were active with G0, 258 were minors with G1, 97 were moderate with G2, 18 were major with G3, and 9 were severe with G4, with the strongest storm being recorded on 22 Jun 2015 with an ap-value of 236 nT, which was classified as a severe storm with G4. Whereas the classification outcomes for the Ap-index recorded 4017 storms: 2032 were very quiet, 958 were quiet, 729 were unsettled, 218 were active (G0), 69 were minor (G1), 9 were moderate (G2), and 2 were strong (G3), and there were no severe or extreme storms (G4 and G5). Meanwhile, on 17 March 2015, a strong storm with a G3 class was recorded with an Ap-value of 108 nT. The study demonstrates the effectiveness of the proposed unified criterion in capturing all relevant physical variations of the selected indices. The classification results indicated that the studied results exhibited a significant increase in counts of GMSs during periods of solar maximum and, on the other hand, a decrease in the amounts of geomagnetic storms, which is consistent with the approach of the solar cycle toward the minimum phase of solar activity.

Keywords: : Geomagnetic storm, Geomagnetic indices, Dst-index, ap-index, Ap-index

Topic: Earth Physics and Space Science