Temporal and Spatial Variations of Total Electron Content Enhancements During a Geomagnetic Storm on 27 and 28 September 2017

Abstract

Temporal and spatial evolutions of total electron content (TEC) and electron density in the ionosphere during a geomagnetic storm that occurred on 27 and 28 September 2017 have been investigated using global TEC data obtained from many Global Navigation Satellite System stations together with the ionosonde, geomagnetic field, Jicamarca incoherent scatter and Super Dual Auroral Radar Network (SuperDARN) radar data. Our analysis results show that a clear enhancement of the ratio of the TEC difference (rTEC) first occurs from noon to afternoon at high latitudes within 1 hr after a sudden increase and expansion of the high‐latitude convection and prompt penetration of the electric field to the equator associated with the southward excursion of the interplanetary magnetic field. Approximately 1–2 hr after the onset of the hmF2 increase in the midlatitude and low‐latitude regions associated with the high‐latitude convection enhancement, the rTEC and foF2 values begin to increase and the enhanced rTEC region expands to low latitudes within 1–2 hr. This signature suggests that the ionospheric plasmas in the F2 region move at a higher altitude due to local electric field drift, where the recombination rate is smaller, and that the electron density increases due to additional production at the lower altitude in the sunlit region. Later, another rTEC enhancement related to the equatorial ionization anomaly appears in the equatorial region approximately 1 hr after the prompt penetration of the electric field to the equator and expands to higher latitudes within 3–4 hr.

Relationship Between the Locations of the Midlatitude Trough and Plasmapause Using GNSS‐TEC and Arase Satellite Observation Data

“…Therefore, we need to exclude the average TEC value during the geomagnetically quiet periods to magnify the signature of midlatitude trough associated with geomagnetic storms and substorms. In this analysis, we use the normalized TEC difference as the ratio of the TEC difference (rTEC) introduced by Sori et al (2019) and Shinbori et al (2020). The rTEC value can be obtained by normalizing the TEC difference between the TEC value every day and average quiet-day TEC value using the absolute value of the average TEC.…”

The Occurrence Feature of Plasma Bubbles in the Equatorial to Midlatitude Ionosphere During Geomagnetic Storms Using Long‐Term GNSS‐TEC Data

“…In this study, we calculated the absolute TEC using dual-frequency carrier phase and pseudorange in the RINEX files, based on the method reported by . Details of the data processing were described in Sori et al (2019) and Shinbori et al (2020). Further, we derived the ROTI to identify ionospheric irregularities related to plasma bubbles.…”

“…Li et al, 2012). These storm-time disturbance electric field variations have been studied based on observational data by using ionosondes (Abdu, Batista, et al, 2003;Tulasi Ram et al, 2016), magnetometers (Galav et al, 2011;Huang et al, 2005;Kikuchi et al, 2008), SuperDARN radars (Kikuchi et al, 2010;Thomas et al, 2013), incoherent scatter radars (Foster & Rich, 1998;Gonzales et al, 1979;Shinbori et al, 2020) and low orbit satellites (Basu et al, 2007;Burke et al, 2000).…”

Model-based reproduction and validation of the total spectrum of solar flare and their impact on the global environment at the X9.3 event of September 6, 2017

“…[14] The TEC in the Earth's ionosphere can be obtained from the radio propagation delay between GNSS satellites and receivers (Otsuka et al, 2002;Tsugawa et al, 2018;Shinbori et al, 2020). Figure 3 shows the global distribution of verticalized TEC processed, and provided by National Institute of Information and Communications Technology (NICT) and Nagoya University.…”