Diagnostic Analysis of the Physical Processes Underlying the Long‐Duration O/N₂ Depletion During the Recovery Phase of the 8 June 2019 Geomagnetic Storm

Abstract

A thermospheric O and N2 column density ratio (∑O/N2) depletion with long‐duration (>16 hr) was observed by the Global‐scale Observations of the Limb and Disk at the Atlantic longitudes (75° ${}^{\circ}$W–20° ${}^{\circ}$W) and middle latitudes (20N–50° ${}^{\circ}$N) during the recovery phase of the 8 June 2019 geomagnetic storm. The National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) simulations reproduced the ∑O/N2 depletion patterns with a similar magnitude, and indicated that the composition recovery at middle latitudes began several hours after the beginning of the recovery phase of the geomagnetic storm. The TIEGCM simulations enable quantitative analysis of the physical mechanisms driving the middle‐latitude composition changes during the storm recovery phase. This analysis indicates that vertical advection and molecular diffusion dominated the initial recovery of composition perturbations at middle latitudes. Horizontal advection was also a main driver in the initial recovery of composition, but its contribution decreased rapidly. In the late recovery phase, the composition recovery was mainly determined by horizontal advection. In comparison, vertical advection and molecular diffusion played a much less important role.

Investigation of the Southern Hemisphere Mid‐High Latitude Thermospheric ∑O/N2 Responses to the Space‐X Storm

“…As already demonstrated in many previous studies, middle and upper thermosphere composition variations during storms are determined by vertical advection, horizontal advection, and molecular diffusion (Burns et al., 1989; 2006; Cai et al., 2020; Cai, Burns, Wang, Qian, Solomon, et al., 2021; Cai et al., 2022; Sutton et al., 2015; Yu, Wang, Ren, Yue, et al., 2021; Yu, Wang, Ren, Cai, et al., 2021; Yu, Wang, et al., 2022). Since diagnostic analysis of the thermosphere composition has been carried out many times in previous studies, here we do not show a detailed diagnostic process, but utilize terms in the continuity equation of thermosphere composition (see details of the equation in Burns et al., 2006; Cai, Burns, Wang, Qian, Solomon, et al., 2021; Yu, Wang, Ren, Cai, et al., 2021), as well as the aforementioned temporal evolution of TN and neutral winds to reveal the underlying mechanism of ΣO/N 2 depletion during the Space‐X storms.…”

Investigation of the ΣO/N2 Depletion With Latitudinally Tilted Equatorward Boundary Observed by GOLD During the Geomagnetic Storm on April 20, 2020

“…GOLD measures the thermospheric/ionospheric airglow emissions from 134 to 162 nm with a spectral resolution of 0.2 nm during daytime (Eastes et al., 2020) and with a spectral resolution of 0.4 nm at nighttime (Cai et al., 2022a, 2022b; Eastes et al., 2019). The daytime OI 135.6 nm and N 2 LBH bands (140–150 nm) are utilized to derive $${\Sigma}$$O/N 2 , of which images are in the same regions between 120$${}^{\circ}$$W and 20$${}^{\circ}$$E, 60$${}^{\circ}$$S and 60$${}^{\circ}$$N from 6:10 to 22:40 UT every day (Yu et al., 2022). In this study, GOLD observed $${\Sigma}$$O/N 2 in the Northern Hemisphere (NH) with a spatial resolution of 1° × 1° on DOY 110 and 111 are utilized.…”

“…The GOLD Far Ultraviolet imager flies onboard the SES-14 telecommunications satellite, which was launched on 25 January 2018 to the geostationary orbit at 47.5 𝐴𝐴 • W (Eastes et al, 2017). GOLD measures the thermospheric/ionospheric airglow emissions from 134 to 162 nm with a spectral resolution of 0.2 nm during daytime (Eastes et al, 2020) and with a spectral resolution of 0.4 nm at nighttime (Cai et al, 2022a(Cai et al, , 2022bEastes et al, 2019) (Yu et al, 2022). In this study, GOLD observed 𝐴𝐴 Σ O/N 2 in the Northern Hemisphere (NH) with a spatial resolution of 1° × 1° on DOY 110 and 111 are utilized.…”

Mid‐Latitude Ionospheric Response to a Weak Geomagnetic Activity Event During Solar Minimum

“…Resultingly, enlarged neutral temperatures and vertical winds generate the thermospheric composition disturbance: larger increases of the molecular species relative to the atomic ones (A. G. Burns et al., 1995; Prölss, 1980) near the local midnight sector. Then the strengthened equatorward meridional wind transports the composition disturbance equatorward to mid and low latitudes, and corotated toward later local time (A. Burns et al., 2006; Cai, Burns, Wang, Qian, Solomon, et al., 2021; Yu, Cai, et al., 2022; Yu, Wang, et al., 2022; Yu, Wang, Ren, Cai, et al., 2021; Yu, Wang, Ren, Yue, et al., 2021). During the transportation and corotation process, the formed disturbance can also be altered by background winds (Cai, Burns, Wang, Qian, Solomon, et al., 2021).…”