Geomagnetic activity for the Kp = 7.3 geomagnetic storm in November 2023 assessed by observational data

The geomagnetic storm of 4–6 November 2023, driven by an Earth-directed coronal mass ejection (CME), was a significant event marked by a peak geomagnetic activity index (Kp) of 7.3 on a 0–9 scale, indicating severe disturbance in Earth’s magnetic field. This CME-induced storm was characterized by intense auroral displays and reached a G3 level (Dst = −172 nT) around 12:40 UT on 5 November, with auroras observed at midlatitudes across Europe. This study examines the effects of the storm on the horizontal (H), declination (D), and vertical (Z) components of the geomagnetic field using data from sunlit-side magnetometer measurements. Planetary activity levels were assessed using traditional Kp and Dst indices from subauroral observatories. Additionally, the newer open-ended Hp30 (half-hourly) and its linear counterpart, ap30, indices were applied to achieve a higher temporal resolution than traditional Kp, providing nuanced insights into the dynamics of the storm. The results show that peak geomagnetic field values closely followed CME-driven solar activity, with midlatitude observatories displaying coherent field pattern shifts, while high-latitude stations had more varied responses. Magnetic observatories near the magnetic equator recorded higher geomagnetic component magnitudes than those at midlatitudes, highlighting latitudinal variations in responses to CME-induced disturbances. By showing the value of the Hp30 and ap30 indices in capturing finer temporal variations, this study offers a refined approach for assessing geomagnetic storms in geomagnetic research.