Topside Ionospheric Reconstruction from LEO Slant TEC Using Smooth Profile Parameterizations

Many reconstructions of ionospheric electron density still rely on spherical symmetry or related assumptions that suppress horizontal structure, while more general voxel based inversions often introduce a very large number of unknowns and become difficult to constrain with the available measurements. We build on earlier work comparing ionospheric profile parameterizations with incoherent scatter radar and reconstructing density from slant TEC using parameterized electron density models and extend it to topside reconstruction using slant TEC from low Earth orbit satellites. The electron density is represented by a chosen family of vertical profiles whose parameters are allowed to vary smoothly along the orbit. Over short orbital windows, the satellite track is treated as a disk like domain, and the parameter fields on that domain are represented with a periodic angular description and a smooth radial dependence. This reduces the number of unknowns while relaxing spherical symmetry and preserving physically interpretable structure in the topside ionosphere. We compare several profile families motivated by earlier midlatitude and topside studies, and we test the method under quiet and disturbed conditions using independent measurements when available. Numerical experiments will also examine how the same framework can be adapted to standard radio occultation and mutual radio occultation geometries for both Earth and Mars.