Toward a Dynamic Model for Topside Ionospheric Irregularities: Spherical Harmonic Decomposition

Abstract Ionospheric irregularities arise from highly dynamic and turbulent processes related to magnetosphere‐ionosphere coupling and can lead to electromagnetic signal distortion or loss of lock events in global navigation satellite system signals, representing a hazard associated with space weather events. For this reason, understanding and modeling these irregularities and their turbulent nature have become increasingly important. In this study, we present a novel dynamic model that characterizes meso‐scale topside ionospheric irregularity and turbulence indices for different magnetic latitudes, magnetic local times, seasons, solar activity and interplanetary magnetic field orientations (IMF) at high latitudes of both hemispheres. To this aim, we used electron density data at 1 Hz cadence acquired by the Swarm mission in the topside ionosphere and covering 10 years of observations. Our model, based on spherical harmonic decomposition, provides statistical maps of (a) electron density, (b) Rate Of change of electron Density Index (RODI), and (c) a proxy for ionospheric turbulent processes, for fixed solar activity level, local season and IMF orientation as specified by the user. The validation tests demonstrate the model's capability in reproducing the features observed at Swarm altitudes for the analyzed parameters. These promising results pave the way for future applications aimed at forecasting possible space weather hazards associated with the development of turbulent ionospheric irregularities.