Detection of high-latitude ionospheric structures using GNSS

Abstract

For detection of rather large ionospheric structures (such as high-latitude ionospheric troughs, main ionospheric trough, etc.) using Global Navigation Satellite Systems (GNSS) we suggest employing the analysis of anomalous deviations in behavior of the absolute slant total electron content (TEC) on particular “GNSS receiver - GNSS satellite” lines of sight (LOSs). Using data of four high-latitude GNSS-stations, the proposed method allowed us to detect the 5 May 2013 high-latitude ionospheric trough (HLIT), determine its location and size, and follow the dynamics. The HLIT was located on the dayside within 25-185°E. Initially (04:40–06:00 UT), the HLIT equatorial wall and bottom were within 68-78°N and 70-80°N, respectively. The trough northern wall was not registered at this time, most likely due to insufficient number of LOSs. During the next hour (06:00–07:00 UT), the trough has moved 2-4° southward. Its bottom lay near 68-76°N; equatorial and polar walls were within 67-74°N and 77-78°N, respectively. The trough width was about 4°. At 07:00–08:00 UT, the HLIT structure and location remained almost the same. To interpret the observation results, we used the model for ionosphere-plasmasphere coupling (developed at the Institute of Solar-Terrestrial Physics SB RAS) to simulate the high-latitude ionosphere conditions on 4–6 May 2013. This simulation showed that on 5 May 2013, a high-latitude trough was formed on the dayside at 40-200°E and 78-85°N. The most likely reason for the formation of HLIT both in model calculations and in reality was a change in the magnetospheric convection in the high-latitude ionosphere caused by the moderate geomagnetic disturbances (substorms) on 4–5 May 2013. The trough location determined from the analysis of anomalous TEC deviations on particular LOSs was in good agreement with location of the high-latitude ionospheric trough obtained from numerical simulation. Thus, the analysis of anomalous deviations in TEC behavior on particular LOSs expands the GNSS potential in detecting large-scale irregularities in the ionosphere.