Ionospheric Responses to the June 2015 Geomagnetic Storm from Ground and LEO GNSS Observations

Chao Gao,Shuanggen Jin,Liangliang Yuan

doi:10.3390/rs12142200

Abstract

Geomagnetic storms are extreme space weather events, which have considerable impacts on the ionosphere and power transmission systems. In this paper, the ionospheric responses to the geomagnetic storm on 22 June 2015, are analyzed from ground-based and satellite-based Global Navigation Satellite System (GNSS) observations as well as observational data of digital ionosondes, and the main physical mechanisms of the ionospheric disturbances observed during the geomagnetic storm are discussed. Salient positive and negative storms are observed from vertical total electron content (VTEC) based on ground-based GNSS observations at different stages of the storm. Combining topside observations of Low-Earth-Orbit (LEO) satellites (GRACE and MetOp satellites) with different orbital altitudes and corresponding ground-based observations, the ionospheric responses above and below the orbits are studied during the storm. To obtain VTEC from the slant TEC between Global Positioning System (GPS) and LEO satellites, we employ a multi-layer mapping function, which can effectively reduce the overall error caused by the single-layer geometric assumption where the horizontal gradient of the ionosphere is not considered. The results show that the topside observations of the GRACE satellite with a lower orbit can intuitively detect the impact caused by the fluctuation of the F2 peak height (hmF2). At the same time, the latitude range corresponding to the peak value of the up-looking VTEC on the event day becomes wider, which is the precursor of the Equatorial Ionization Anomaly (EIA). However, no obvious response is observed in the up-looking VTEC from MetOp satellites with higher orbits, which indicates that the VTEC responses to the geomagnetic storm mainly take place below the orbit of MetOp satellites.

Highlights

The geomagnetic storm is a severe global disturbance of the Earth’s magnetic field, usually under the impact of disturbances in the solar wind and Interplanetary Magnetic Field (IMF) with their origins near the solar surface
We investigate the intense geomagnetic storm on 22 June 2015, and analyzed the responses of vertical total electron content (VTEC) with different altitude ranges during the storm
Ground- and satellite-based Global Navigation Satellite System (GNSS) observations as well as observational data of digital ionosondes are used to study the responses of VTEC with different altitude ranges to the intense geomagnetic storm that occurred on June 22, 2015, which is the second largest geomagnetic storm in the 24th solar cycle

Summary

Introduction

The geomagnetic storm is a severe global disturbance of the Earth’s magnetic field, usually under the impact of disturbances in the solar wind and Interplanetary Magnetic Field (IMF) with their origins near the solar surface. Most studies used ground- or satellite-based GNSS observations during a geomagnetic storm in the past, while ionospheric responses at different altitudes are not clear. Based on ground-based and satellite-based GNSS observations as well as observational data of digital ionosondes, the ionospheric response to the intense geomagnetic storm on 22 June 2015 is studied in this paper. The distribution of ionospheric vertical TEC (VTEC) in the low- and mid-latitude regions along ~120◦E (110◦E–130◦E, 60◦S–60◦N) is obtained by ground-based GNSS observations during the intense geomagnetic storm. Through combination of the topside observations of LEO satellites with the ground-based GNSS observations in corresponding time and space, variations of VTEC with different altitude ranges throughout the whole storm event are studied, and the possible causes and physical mechanisms of the variations are explained.

Observational Data

Interplanetary and Geomagnetic Indexes

Ionospheric Responses From Ground Observations

Conclusions and Discussion