Monitoring Ionospheric Gradients using Swarm onboard GPS and Langmuir-probe data

Abstract

Within the scope of MIGRAS, a project of Swarm DISC, we developed two new data products that focus on monitoring mid-scale plasma density irregularities with horizontal spatial scales in the order of about 100 km utilizing measurements from the Swarm satellites A and C in polar orbits at heights of about 460 km. Two new Swarm products are the total electron content (TEC) Gradient Ionosphere indeX (TEGIX) and the electron density (NE) Gradient Ionosphere indeX (NEGIX) derived from topside TEC and in-situ electron density measurements onboard GPS receivers and Langmuir probes. The TEGIX and NEGIX results during the St. Patrick‘s Day Storm on 17th March 2015 will be shown and discussed for both North-South and West-East components. For the same storm day, the NEGIX and TEGIX products are validated against the Gradient Ionosphere IndeX (GIX) derived from numerous ground GNSS stations data over the European region. We found that the North-South component of TEGIX and NEGIX products correlate very well with the same component of the ground-based GIX data. A prototype data product of NEGIX and TEGIX has been produced for the time period 2018-01-01 until 2018-06-30. The data set has nearly 2 million records of estimated density gradient TEGIX and NEGIX vectors. Considering six months of data, NEGIX is validated using basic statistical tests. Clear terminator related gradients at sunrise and sunset, i.e. ~6 and ~18 LT are observed. The NEGIX product shows consistent results with gradients at equatorial crests ~+/- 20 deg and also signatures of the mid-latitude ionospheric trough (MIT) at ~+/- 60 deg latitude. A use case of NEGIX for ionospheric scintillation modelling is discussed. An innovative scintillation modelling technique shows that the large gradients of electron density visible in the NEGIX are associated with high phase scintillation occurrence.