Estimation of GPS-based ionospheric indices by GIX, SIDX, and ROTI during the St. Patrick’s Day geomagnetic storm event in the Indian low latitude region

Abstract The disturbance in ionospheric conditions caused by geomagnetic storms leads to problems with the ground, satellite communication, and navigation technology. The Ionospheric perturbations affect the accomplishment of the Global Navigation Satellite System (GNSS), namely accuracy, continuity, availability, and integrity. During the ionosphere’s disturbance level, the Precision and safety of GNSS applications are essential to obtain data about space weather conditions. Along different GNSS satellite receiver paths, GNSS receivers are particularly vulnerable to expeditious changes in Total Electron Content (TEC) and critical spatial variations. The ionospheric indices, namely the Gradient Ionosphere Index (GIX), Rate of TEC Index (ROTI), and the Sudden Ionospheric Disturbance Index (SIDX), are employed for monitoring ionospheric conditions. The ionospheric disturbances can be assessed using GIX and SIDX without prior data. These indices have been modeled and validated based on GNSS observations provided by the Indian region. This research work examines the effects of the ionosphere on the St. Patrick’s Day geomagnetic storm (17th March 2015) by inspecting TEC variations from March 14 to 19, 2015, using spatial and temporal indices for GNSS stations at Trivandrum, Hyderabad, Mumbai, Kolkata, Bhopal, Delhi positioned in the Indian subcontinent. In low-latitude regions, the highest GIX, ROTI, and more negative SIDX values started recording from 1,200 h UT to 1,500 h UT on 17th March 2015. On 17th March 2015, during the storm’s main phase, the selected stations showed GIX values ranging from 47.2 to 103.3 m TECU/km. On Recovery Day 19th March 2015, GIX readings range from 38.1 to 60 m TECU/km, this research plays a part in understanding ionospheric gradients in the equatorial and low latitudes, where it is applicable for improving Ground Based Augmentation Systems (GBAS) and GPS-aided GEO Augmented Navigation (GAGAN) effective for aircraft landing.