Classifying and bounding geomagnetic storms based on the SYM-H and ASY-H indices

Geomagnetic storms, which are significant disturbances in Earth’s magnetic field, pose a natural hazard with potentially harmful effects on technological and electrical systems. Various indices such as Kp, Dst, and the newer SYM-H and ASY-H are used to measure storm intensity. However, there is no consensus among researchers regarding storm classification based on intensity and asymmetry for the SYM-H and ASY-H indices, as existing classifications mainly rely on the Dst and Kp indices. This study proposes a classification method based on the cumulative distribution function of the SYM-H and ASY-H indices, applying industry-wide percentiles to determine storm classes. Using percentiles and a superposed epoch analysis, storms are objectively classified based on intensity and occurrence probability. This classification approach has applications in storm forecasting and risk assessment.