Introduction of new navigation signals L2C (1227.60 MHz) and L5 (1176.45 MHz) to the existing GPS (Global Positioning System) spectrum, under the modernization program of GPS offers the improvement of position accuracy. The present study aims to understand the relative robustness of the L2C and L5 signals compared to legacy L1 C/A signal during periods of scintillations in terms of durations of cycle slips encountered from an anomaly crest location, Calcutta (22.58°N, 88.38°E geographic; magnetic dip 32°N). The data analyzed in this study were recorded during the vernal equinox of 2014 (February–April), a period of high solar activity of cycle 24. Results obtained from the comparative analyses, which are perhaps one of the first from the Indian longitude sector, indicate GPS L5 to be more robust than L1 C/A and L2C in terms of occurrence and duration of cycle slips under adverse ionospheric conditions. Furthermore, loss‐of‐lock events of duration greater than 6 s are found to be more frequent for S₄ ≥ 0.6. It is found that frequency sensitivity of the GPS spectrum, in terms of occurrence of cycle slips and loss of locks are in conformity with earlier results from the equatorial region but are different from the high latitudes with respect to local time of occurrence and geomagnetic activity.

This study examines the ionospheric response to the intense geomagnetic storm of 9–12 October 2024 over the European sector. Digisonde data from mid-latitude European stations and in situ electron density measurements from Swarm A and B satellites were used to analyze variations in key ionospheric characteristics, including the critical frequency (foF2), peak height (hmF2) and plasma drift velocities. Significant uplift of the F2 layer and a corresponding reduction in foF2 were observed across latitudes, primarily driven by prompt penetration electric fields (PPEFs) and storm-induced thermospheric winds. Horizontal and vertical ion drifts showed large asymmetries and reversals, with zonal drift velocities exceeding 1000 m/s at some stations. Swarm observations confirmed plasma density enhancements during the main phase and notable depletions during recovery, particularly after 1:00 UT on 11 October. The midlatitude ionospheric trough (MIT) intensified during the recovery phase, as can be seen from Swarm B. These variations were shaped by electrodynamic forcing, compositional changes and disturbance dynamo electric fields (DDEFs). The results emphasize the role of solar wind drivers, latitude-dependent electrodynamic coupling and thermospheric dynamics in mid-latitude ionospheric variability during geomagnetic storms.

A major earthquake with a magnitude of M _W = 7.7, followed by several aftershocks, occurred in Mandalay, Myanmar, on 28 March 2025. This study aims to report on the co‐seismic ionospheric disturbances caused by the event, based on a multi‐instrument approach that was adopted to examine co‐seismic effects. Frequency analysis and filtering techniques were employed to distinguish between different acoustic or gravity wave signatures in the ionosphere. Ground seismic stations provided wave velocity estimation, while the velocity of co‐seismic ionospheric wavefronts was estimated using Total Electron Content fluctuations from GNSS receivers. Using the collocation of a seismic station with an Ionosonde station, it has been possible to estimate the vertical propagation time of acoustic waves, resulting in multi‐cusp signature formation. Additionally, radio occultation electron density profiles from the COSMIC‐2 mission have been analyzed in search of topside signatures. While horizontal velocities of co‐seismic ionospheric wavefronts were estimated between 0.8 and 3.6 km/s, their non‐isotropic distribution with epicentral distance revealed information about the background generation mechanism. For each seismic event, studies related to the co‐seismic ionospheric behavior could provide insightful information relating the coupling between ground and upper atmosphere. This study exploits a combination of data sets for a comprehensive understanding of the ionospheric disturbances associated with an earthquake.