Response of the Ionosphere‐Plasmasphere Coupling to the September 2017 Storm: What Erodes the Plasmasphere so Severely?

Abstract

We report an extreme erosion of the plasmasphere arising from the September 2017 storm. The cold electron density is identified from the upper limit frequency of upper hybrid resonance waves observed by the Plasma Wave Experiment instrument onboard the Exploration of energization and Radiation in Geospace/Arase satellite. The electron density profiles reveal that the plasmasphere was severely eroded during the recovery phase of the storm and the plasmapause was located at L = 1.6–1.7 at 23 UT 8 September 2017. This is the first report of deep erosion of the plasmasphere (LPP < 2) with the in situ observation of the electron density. The degree of the severity is much more than what is expected from the relatively moderate value of the SYM‐H minimum (−146 nT). We attempt to find a possible explanation for the observed severe depletion by using both observational evidence and numerical simulations. Our results suggest that the middle latitude electric field had penetrated from the high‐latitude storm time convection for several hours. Such an unusually long‐lasting penetration event can cause this observed degree of severity.

Effects of the 10 September 2017 Solar Flare on the Density and Composition of the Thermosphere of Mars

“…At Earth, the solar activity of these September 2017 storms affected the geospace environment significantly. Earth's plasmasphere was severely eroded (Obana et al., 2019), and at lower altitudes, a CME shock increased the outflow flux of O + from the ionosphere to three times a baseline value already elevated by the earlier impacts of X‐class flares and another shock (Schillings et al., 2018). The CMEs and their associated SEPs corresponded to decreased intensities of cosmic rays (Forbush decreases) as the changing interplanetary magnetic field deflected a greater proportion away from Earth (Badruddin et al., 2019; Chertok et al., 2018).…”

“…The intense solar effects at Earth impacted critical technological systems. The performance of GPS and similar navigation systems were degraded by enhanced solar radio noise at the GPS frequencies and by temporal variations in ionospheric total electron content (Berdermann et al., 2018; Linty et al., 2018; Obana et al., 2019). In addition, high‐frequency (3–30 MHz) radio communications, which rely upon reflections from the ionosphere to propagate beyond the horizon, were disrupted due to the perturbed state of the ionosphere (Aa et al., 2019; Bland et al., 2018; Chakraborty et al., 2019; Curto et al., 2018; Yamauchi et al., 2018; Yasyukevich et al., 2018).…”

Identification of potential precursors for the occurrence of Large-Scale Traveling Ionospheric Disturbances in a case study during September 2017

“…We chose for our case study the 7-8th September 2017 geomagnetic storm, which is a part of the intense solar and geomagnetic disturbances that started on 6th September 2017. These disturbances generated many space weather phenomena, such as, solar flares (Berdermann et al, 2018), solar radio bursts (Sato et al, 2019), and radiation storms (Mavromichalaki et al, 2018;Mishev & Usoskin, 2018), and effects on near-Earth space, such as, plasmasphere erosion (Obana et al, 2019), high-frequency (HF) radio wave absorption and solar flare effects (Sfe, Curto et al, 2018) and ground induced currents (GIC, Dimmock et al, 2019).…”

Detection of UHR Frequencies by a Convolutional Neural Network From Arase/PWE Data

“…The SYM ‐ H minimum and maximum K p during this period were −146 nT and 8 + on 8 September 2017. Obana et al (2019) analyzed UHR frequency variations on the September 2017 storm observed by the HFA and OFA aboard Arase. They reported an extreme erosion of the plasmasphere due to the enhanced convection.…”