Topside Ionospheric Conditions During the 7–8 September 2017 Geomagnetic Storm

• Published in: Journal of geophysical research. Space physics 2019-11, Vol.124 (11), p.9381-9404
• Main Authors: Jimoh, Oluwaseyi, Lei, Jiuhou, Zhong, Jiahao, Owolabi, Charles, Luan, Xiaoli, Dou, Xiankang
• Format: Article
• Language: English
• Subjects: Electric fields; Electron density; Equator; Geomagnetic activity; geomagnetic storm; Geomagnetic storms; Geomagnetism; GRACE (experiment); ionosphere; Ionospheric conditions; Ionospheric electric fields; Ionospheric irregularities; Irregularities; Magnetic storms; rate of electron density index; Recovery; Storms; topside; uplooking total electron content; Variation
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2019JA026590

The uplooking total electron contents (TECs) from the GRACE, SWARM‐A, TerraSAR‐X, and MetOp‐A satellites and in situ electron density (Ne) from SWARM‐A were utilized to investigate the topside ionospheric conditions during the 7–8 September 2017 geomagnetic storm. The rate of TEC index (ROTI) and rate of density index (RODI), which are derivative indices of TEC and Ne, respectively, were also used to characterize the topside ionospheric irregularities. The main results of this study are as follows: (1) There were significant enhancements seen in the uplooking TEC during the first main phase of the storm. (2) The uplooking TEC did not show unusual enhancement at the morning and evening local times in the Asian‐Australian sector during the recovery phase of the storm. (3) Prominent TEC hemispheric asymmetry at the middle and high latitudes was observed at both day and night sectors. (4) Long‐duration recovery of topside TEC with respect to the prestorm condition was also detected in this event. (5) Nighttime ROTI enhancements were presented in a wide latitudinal range from the equator to the poles during the main phases of the storm. (6) The ionospheric electric field disturbances associated with IMF‐Bz fluctuations probably played a very important role in triggering ionospheric irregularities during the relatively weak geomagnetic activity on 7 September, which implies that ionospheric irregularities do not necessarily occur under the severe geomagnetic conditions only. Key Points Long‐duration depletion of topside TEC recovery was observed during the morning and evening local times in this event Enhancements of ionospheric irregularities were presented at night with wide latitudinal range during the two main phases of the storm Ionospheric electric field disturbances due to Bz fluctuations probably triggered topside ionospheric irregularities before the main phases