A hybrid reconstruction approach for estimating topside ionospheric scale height and its altitudinal variation using Jicamarca ISR measurements

In ionospheric research, accurately representing the topside electron density profile is essential for predicting radio wave propagation and mitigating ionospheric effects on communication and navigation systems. Despite advances in global models and satellite observations, region-specific and continuous modelling of the topside ionosphere remains challenging due to limited in-situ measurements. Reliable reconstruction of the topside ionosphere using empirical formulations requires precise knowledge of the scale height at the [Formula: see text] peak ([Formula: see text]) and its linear altitudinal variation (α), especially over the electrodynamically complex equatorial and low-latitude regions. In this study, 13 years (2013-2024) of incoherent scatter radar measurements from the Jicamarca Radio Observatory, Peru, a prominent dip-equatorial station, are utilized to extract realistic topside parameters. A Hybrid reconstruction strategy is employed to adaptively select best suitable formulation between the α-Chapman and semi-Epstein formulations at each time step using fitting error metrics derived from least-square optimization. This approach enables simultaneous and physically consistent estimation of [Formula: see text] and α. The results revealed pronounced diurnal, seasonal, and solar-geomagnetic variability in the topside parameters. Overall, this analysis demonstrates the effectiveness of the Hybrid approach in improving the topside electron density reconstruction, and the insights gained may be integrated with existing models to enhance their regional accuracy.