Ionospheric Reconstruction Using GNSS Signals Around an Anomaly Crest Location in Indian Longitude Sector

Abstract

AbstractThe present study aims to reconstruct the vertical ionospheric electron density (IED) profile using computerized ionospheric tomography (CIT) techniques, over the northern crest of the equatorial ionization anomaly (EIA) which is one of the most geo‐physically sensitive regions of Indian longitude sector. Total electron content (TEC) measurements obtained from GNSS signals from receivers located at Kolkata (22.57°N, 88.36°E), Purulia (23.33°N, 86.36°E), and Siliguri (26.73°N, 88.39°E) and International GNSS Service (IGS) stations of Port Blair (11.64°N, 92.71°E), Bangalore (13.02°N, 77.57°E), Hyderabad (17.42°N, 78.55°E), Lucknow (26.91°N, 80.96°E) and Lhasa (29.66°N, 91.10°E) have been incorporated into the tomography algorithm for ionospheric reconstructions. Among the different iterative techniques used for retrieving IED profiles on a 2‐dimensional altitude versus latitude plane fixed at a certain longitude, simultaneous iterative reconstruction technique (SIRT) was shown to be the optimum choice based on the representation of the EIA phenomenon and reconstruction accuracy. A comparative assessment between two ionospheric models IRI2016 and PIM1.4 was performed, with PIM based initial guess for inversions resulting in lower reconstruction errors. The 2D CIT algorithm was then used to reconstruct the hourly vertical IED profiles to study the impact of the severe G4‐class St. Patrick's Day storm on 17 March 2015 and reconstructed electron densities showed a large increase over the values obtained from the geomagnetically quiet day of 10 March 2015, indicating a positive ionospheric storm phase. Ionospheric response to the G1‐class geomagnetic disturbance on 5 December 2017 and the average F‐region IED values have also been compared with a geomagnetically quiet day of 3 December 2017.