Investigating the Influence of Lightning on Ionosphere over Bangladesh Using WWLLN and GNSS Observations

This study investigates the influence of lightning on the occurrence of ionospheric irregularities over Bangladesh based on the World Wide Lightning Location Network (WWLLN) and Global Navigation Satellite System (GNSS) dataset of 2023. The ionospheric irregularities solely caused by lightning are determined by extracting the total electron content (TEC) of the ionosphere during the geomagnetically quiet days of 2023 having a Kp-index value of less than 4. The data from GNSS is processed through the GNSS TEC algorithm to derive the Vertical TEC (VTEC) data which is used to compute the rate of the TEC index (ROTI). Statistical analysis is performed on ionospheric irregularity events (IIE) over Bangladesh, specifically focusing on instances where ROTI exceeded a threshold of 0.8 TECU/min. The results show that about 1,344 occurrences of IIE were found by using six GNSS stations over Bangladesh. The correlation between IIE and lightning stroke shows that the IIE/hour reaches its peak at around 12:00 UT whereas stroke/hour reaches its peak at 20:00 UT. However, both the IIE and Lightning stroke rates show a similar pattern at 12:00 UT. In 2023, the diurnal correlation between the IIE/hour and the stroke/hour is found to be 74%. To examine the diurnal patterns of lightning and its ionospheric effects, two case studies have been conducted. June 17, 2023, is chosen for analysis due to its maximum lightning counts of 16,775. The results show that the lightning stroke rates peaked at 05:00 UT with a secondary peak at 12:00 UT, and the concurrent ionospheric variability (∆VTEC) is observed from 05:00 to 15:00 UT. The second case study is conducted on 18 October 2023, considering ROTI above 0.8. On that day, the lightning stroke peak varies from 1800 to 6000 whereas the TEC variability (∆VTEC) curve fluctuates throughout the day. Therefore, the study concludes that lightning activity significantly impacts ionospheric disturbances, which in turn affects radio wave propagation.