A Hybrid Correlation Model for the Spaced-Receiver Technique Radio Science

A Global Navigation Satellite System (GNSS) spaced-receiver technique estimates ionospheric irregularity drift velocity by correlating the received GNSS signals across a closely spaced receiver array during ionospheric scintillations. This paper focuses on the correlation models accounting for the topology of the received diffraction pattern. Space-time correlation schematics are developed to analyze and compare several prevalent models, including the classic isotropy model, the front velocity model, and the anisotropy model. Based on the merits and drawbacks of each model, a hybrid correlation model is proposed, integrating the front velocity model and the anisotropy model. To validate the hybrid model, the corresponding drift velocity estimates are cross compared with the measurements from a colocated all-sky imager and incoherent scatter radar. A case study was conducted for a geomagnetic storm event on 20 December 2015. Favorable agreement was found in terms of direction and magnitude of the drift motion, orientation of the irregularity, temporal and spatial features of the irregularity, and the statistical behavior of the drift velocity estimates. In addition, the root-mean-square velocity magnitude and orientation against the incoherent scatter radar measurements demonstrate the superior performance of the hybrid model.