Analysis of the Regional Ionospheric Disturbance Index During Geomagnetic Storm in 2012

The impacts of severe geomagnetic storms that occurred in 2012 on the emergence of large-scale ionospheric anomalies in the equatorial region of Malaysia was investigated in this study. The research analyzed three significant geomagnetic storms that happened on April 24 (−120 nT), July 16 (−113 nT), and October 01 (−122 nT) of 2012. Their effects were assessed across different locations identified by the latitudes and longitudes 4°N 99°E, 3.06°N 101.54°E, 4.18°N 102.04°E, 3.16°N 113.03°E, 6.07°N 116.07°E, and 6.30°N 99.78°E respectively. Total Electron Content (TEC) from the GPS network over Malaysia was assessed by comparing the TEC during the three main phases of geomagnetically disturbed days with the average profiles of TEC during the quiet period. To determine the level of perturbation, the log of TEC was calculated in relation to the quiet reference median of 15 quiet days prior to the observation days. To represent the influence of the geomagnetic storms on TEC in Malaysia, a disturbance index was utilized. The thresholds of the index were established to indicate the level of disturbance, with positive and negative signatures of ±1 representing a quiet state, and ±2 indicating a moderate disturbance. A moderate ionospheric storm was indicated by ±3, while a severe ionospheric storm was represented by ±4. Based on the three events chosen, the threshold of the disturbance index indicated a severe storm on April 23, 2012 at 1900 UT, which was early morning of April 24, in the Malaysian region, while the other two storms indicated no severe storm, with the index ranging from ±1 to ±3 only. The study found that positive and negative disturbances in the ionosphere were a common occurrence. The impact of the storms was observed to persist before and after the actual storm period. This emphasizes the importance of having a dedicated ionospheric weather index in addition to geomagnetic indices over the equatorial region to evaluate and predict the impact of space weather storms, thus enhancing the precision and reliability of radio systems that are vulnerable to ionospheric disruptions.