Analysis of disturbance dynamo and plasma bubble phenomena over Malaysia during the May 2024 geomagnetic storm

This study presents the first observational report of ionospheric disturbance dynamo (Ddyn) signatures derived from Malaysian magnetometer stations and examines their relationship with equatorial plasma bubble (EPB)-related ionospheric irregularities during the extreme geomagnetic storm of 10–11 May 2024. Ddyn signatures were identified from perturbations in the horizontal magnetic field recorded at Langkawi (LKW), Ranau (RAN), Terengganu (TRE), and Johor (JOH), while EPB activity was evaluated using single-station ROTI observations and regional ROTI keograms. The storm exhibited a two-step main phase with Dst minima of −351 nT and −412 nT, followed by an approximately 11-day recovery phase. The strongest Ddyn response occurred at LKW, whereas no distinct Ddyn signature was identified at JOH. Analysis of ROTI observations and regional keograms revealed the occurrence of EPBs on 10 and 13 May 2024, but not during the interval when Ddyn was present. Although the observations do not establish a direct causal relationship between Ddyn and EPB occurrence, they reveal a clear temporal correspondence between storm-time Ddyn activity and changes in post-sunset ionospheric irregularities. These results provide new observational evidence of storm-time ionospheric electrodynamics over the Malaysian equatorial sector during an extreme geomagnetic storm.