Web application for retrospective geomagnetic storm detection, main phase analysis and identification of solar wind influence on storm intensity

Abstract

This work presents a web application for retrospective detection and analysis of geomagnetic storms using hourly Dst and solar wind data from OMNIWeb. The application detects storm events, identifies their main phases, computes solar wind derived parameters during the main phase, and examines their relationship with storm intensity. Its detection and main phase identification parameters are user-adjustable, allowing different assumptions to be tested interactively rather than imposed through a single fixed parameter set. OMNIWeb data from 1964 through May 2026 were analyzed. Using the default parameter set, 1796 storms with Dst_min <= -50 nT were detected, including 1422 moderate storms (-100 < Dst_min <= -50 nT), 347 intense storms (-250 < Dst_min <= -100 nT), and 27 super-storms (Dst_min <= -250 nT). After filtering for reliable main phase identification, 1643 storms were retained. The average main phase duration per class was 9.25 hours for moderate storms, 11.30 hours for intense storms and 13.75 hours for super-storms. After also requiring OMNIWeb solar wind data availability, 990 storms remained for examining the relationship between storm intensity and solar wind derived parameters over the main phase. The strongest correlations with |Dst_min| were obtained for peak dawn-dusk electric field (Eyp; R = 0.836), peak southward IMF (Bzp; R = -0.811), and integrated electric field (Eyi; R = 0.759). These results confirm the importance of the solar wind electric field and southward interplanetary magnetic field in geomagnetic storm development. The main contribution of the application is its adjustable detection framework, which allows users to explore how parameter choices affect storm detection, main phase identification, and solar wind association results. All outputs are downloadable for further user-defined analysis. The application is available at: https://geomagnetic-storm-mainphase-analysis.streamlit.app/