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A digital ionosonde was designed and built by Society for Applied Microwave Electronics Engineering and Research (SAMEER), Mumbai in collaboration with Dibrugarh University to suit the needs of equatorial-and low-latitude regions of India. The design objectives were to obtain good signal-tonoise ratio to mitigate the heavy noise due to interference, obtain short duration ionograms, estimate vertical drifts, reconstruct vertical electron density profile, and make antenna size smaller. Transmission of maximum 1 kW power using modified delta antenna is used with dual channel magnetic loop receiver antenna. Pulse compression by 8-and 16-bit biphase codes are employed to increase noise immunity and the height resolution. The preliminary results of the ionogram mode only are presented in this work. The basic ionogram recorded by this system called SAMEER-Dibrugarh University Ionospheric Radar is compared with colocated Canadian Advanced Digital Ionosonde ionogram which is in operation in Dibrugarh since 2010. A reasonably clear trace of E and F layers is obtained even without coherent pulse integration and pulse coding. The performance of the coding schemes is investigated with and without coherent integration. Some sample ionospheric experiments conducted with SAMEER-Dibrugarh University Ionospheric Radar, and interesting results like the detection of travelling ionospheric disturbances, Es layer substructures, ionospheric irregularities, and the generation of bottom-side vertical electron density profile are presented to highlight the potential and capabilities of the system. Plain Language SummaryA new high-frequency sweeping radar or digital ionosonde was designed and developed by SAMEER, Mumbai in collaboration with Dibrugarh University. This type of radar is used for monitoring ionospheric conditions for high-frequency band and trans-ionospheric communications like Global Positioning System signals. Additionally, it has been one of the oldest but still relevant tool for research in the field of ionosphere.

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The inter-hemispheric difference in the impact of the geomagnetic storms of June 2015 and December 2015 is investigated with respect to quiet time seasonal asymmetry. A meridional chain of ground observatories along 95°E (GNSS receiver/Ionosonde), satellite in-situ measurements (SWARM/COSMIC/C-NOFS), Total Electron Content map and SAMI2/CTIPe model simulations are utilized. Symmetric negative (positive) effects prevailed during the main phase of June (December) storm but hemispheric asymmetry was manifested during the recovery phase. Differential VTEC and NmF2 response in addition to perturbations in VTEC by more than 30 TECU (~90-100%) were recorded. The SWARM observations confirmed that the topside density/TEC enhancement in the southern low latitude was much higher than 300%. The SWARM A/B pass of 23 June and ground TEC map showed a third latitudinal maxima around -45° dip angle in southern hemisphere low latitude in addition to the conventional EIA crests. Similarly an additional peak appeared at +45° dip in northern hemisphere in the SWARM A pass in the sunrise period of 21 December. The higher winter-side hmF2 and northward C/NOFS meridional flow velocity suggest that storm time Joule heating resulted in anomalous equator-ward winds surge in the winter hemispheres of 95°E which led to the formation of the additional storm time maxima at the pole-ward edge of the EIA region. Further modeling efforts are needed to capture this counter-intuitive feature for a better forecasting of the impact of space weather events over low latitude ionosphere.