A study on the relation between an elevation angle of GNSS measurements and an integrated plasma enhancement of polar patches.

The polar ionosphere is characterized by massive structures, known as patches, resulting from intake of mid-latitude plasma or, to a lesser extent, from particle precipitation. The occurrence of patches is an object of multi-instrumental investigations performed with various space- and ground-based techniques, involving among others the measurements of Global Navigation Satellite Systems. With regard to the latter approach, the patch definition has to be reformulated to the electron density accumulated along a signal path. This step requires an additional validation of the relation between an elevation angle of GNSS measurements and an integrated enhancement of plasma.

The work compares polar patch signatures observed in GNSS time series during a maximum solar activity. The assessment of integrated patch enhancement was realized with relative STEC values that are computed for several GNSS stations located in the northern polar cap. Investigating the results at different elevation angles, one can observe a lack of typical geometrical dependency of relative STEC. We believe this effect is related to an approximately spherical shape of patches. Such a conclusion seems to be confirmed by a similar enhancement observed for measurements with different orientations. According to the obtained results, we find this is justified to use STEC as an indicator of patch enhancement for GNSS data.