Low latitude ionospheric irregularity observations across a wide frequency spectrum from VHF to S-band in the Indian longitudes

This study reports coordinated observation of ionospheric irregularities from VHF Radar, GPS and IRNSS (Indian Regional Navigation Satellite System), from regions near the northern crest of the EIA (Equatorial Ionization Anomaly), which has not been explored earlier. Efforts have been made to study the signal-in-space environment for concurrent detection of ionospheric irregularities over a range of radio frequency, starting from 53 MHz of the Radar, to L-band of GPS at 1,575.42 MHz and S band signal of IRNSS at 2,492.5 MHz. The radar is operational at Ionosphere Field Station, Haringhata (geographic latitude 22.93°N; geographic longitude 88.5I°E; magnetic dip angle 36.2°N) of University of Calcutta. The GPS and IRNSS data are recorded at Calcutta (22.58°N, 88.38°E geographic; magnetic dip: 36°N), separated from Haringhata by 50 km. The spatial as well as temporal variations of irregularities affecting different radio frequencies have been presented. Coordinated observations have been made during period of March-April 2023. Results of the study reveal the common zone of impact of the different radio frequency links spanning from 53 to 2,592.5 MHz and was identified within I6°–25°N, 85°–90°E. During coordinated observations made over several days, irregularity structures have been observed with radar, having backscatter SNR (Signal to Noise ratio) intensity within — 5 to 15 dB. During this time, while intense L band scintillation was recorded on multiple satellites of GPS, scintillation recorded at S band signal was moderate to intense.