[P-EM13] Coupling Processes in the Atmosphere-Ionosphere System

[PEM13-01] On the relation between FORMOSAT-7/COSMIC-2 radio occultation scintillation S4 index and co-located electron density profiles in 2020

*YI DUANN^1,2、Loren Chang^1,2、Chi-Kuang Chao^1,2、Chi-Yen Lin^1,2、Jann-Yenq Liu^1,2、Tung-Yuan Hsiao³、Shih-Ping Chen⁴ (1.Department of Space Science and Engineering, National Central University, Taoyuan City, Taiwan、2.Center for Astronautical Physics and Engineering, National Central University, Taoyuan City, Taiwan、3.Nuclear Science and Technology Development Center, National Tsing Hua University, Hsinchu City, Taiwan、4.Department of Earth Sciences, National Cheng Kung University, Tainan City, Taiwan)

キーワード：Ionospheric scintillation index (S4), FORMOSAT-7/COSMIC-2, Equatorial plasma bubbles (EPBs), Solar minimum, Electron density, Low-latitudes

The current six FORMOSTAT-7/COSMIC-2 (F7/C2) microsatellites orbiting at ∼550 km with 24º inclination, retrieving GNSS-Radio-occultation (RO) profiles within a geographic latitude region of ±40ºN. The abundant data collected by the primary Tri-GNSS RO System carried by F7/C2 provide an opportunity of studying the relation between the ionospheric scintillation amplitude index (S4) and the variation of the electron density (Ne) profile. The F7/C2 RO experiment derived S4 observations at low latitudes are used to understand the development of the equatorial plasma bubbles (EPB) generated during the post-sunset and post-midnight periods in this study. The analysis in this study follows the classification of Chen et al. (2021). The S4 max ≧ 0.125 and S4 max ≧ 0.5 are defined to be related to the seeding EPBs at the bottomside of the ionosphere and the mature EPBs, respectively. The results indicate that the American sector has the highest occurrence rate of S4 max except for during boreal summer, and the boreal winter-summer difference of S4 max occurrence rate during the 2020 solar minimum is large in the northern hemisphere. Additionally, a boreal autumn anomaly of the S4 occurrence rate in the Pacific sector is observed as well. Furthermore, the seasonal pattern of the S4 altitude and its potential relationship with the tidal forcing in the local time frame is analyzed as well, to learn the mechanism of the occurrence of S4 in the F-layer related to the propagating waves. Moreover, the correlations of the altitudes of the S4 max and F7/C2 (∇_zNe)_max within geomagnetic latitude 25ºN-25ºS in the boreal summer and winter are compared in this study as well, revealing that the S4 max has an increasing inverse correlation with the altitudes of (∇_zNe)_max and hmF2 during boreal summer in the Indian sector, but this feature is opposite to the American sector.