Evidence and Causes of an Unusual Super Plasma Bubble Occurrence During Weak Geomagnetic Conditions Over Europe

Using data from a cluster of ground-based global navigation satellite system, we observed spatially extended enhanced ROTI over the European longitudes during a weak geomagnetic storm (Dst (Formula presented.) −50 nT) on 4 November 2023. The enhanced ROTI is extended over an extensive geographical latitudinal range of 46°N. Further analysis using other simultaneous ground-based and satellite measurements reveals that the ROTI enhancement is caused by the super plasma bubble (SPB). For instance, a strong range spread and depletion in total electron content (TEC) were observed in the enhanced ROTI regions. Following this, depletion in TEC and OI135.6 nm irradiance was also observed along similar longitudes and latitudes on the African continent. Simultaneous Swarm-A and C electron density showed plasma depletion between 15°S and 31°N at 10°E, which agrees with the enhanced ROTI data as well. To explore the cause of this enhanced ROTI, the prompt penetration equatorial electric field model (PPEEFM) PPEEFM and magnetometer data have been analyzed. We found a sharp decrease in the geomagnetic field during the evening hours, which suggests the ingression of the prompt penetration electric field (PPEF). The PPEF arrival time coincides with the post-sunset pre-reversal enhancement; consequently, an SPB was generated. This study provides observational evidence of SPB in weak geomagnetic conditions, shedding light on the causative mechanism.