[P-EM36_28PM1] 大気圏・電離圏

[PEM36-20] 大気圏潮汐作用による電離圏夜間中緯度電子密度異常の変化

*陳 佳宏¹、Lin Charles¹、Chang Loren²、Huba J. D.³、齊藤 昭則⁴、劉 正彦² (1.台湾国立成功大学地球科学学科、2.台湾国立中央大学太空科学研究所、3.Plasma Physics Division, Naval Research Laboratory, Washington, D. C., USA、4.日本京都大学理学研究科)

キーワード：中緯度, 電子密度異常, 大気圏潮汐作用

This study use a 3D physics-based ionospheric model, SAMI3, coupled with the National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) and Global Scale Wave Model (GSWM) to simulate the mesospheric and lower thermosphreic tidal effects on the development of midlatitude summer nighttime anomaly (MSNA). Using this coupled model, the diurnal variation of MSNA electron densities at 300 km altitude is simulated on both June solstice (day of year (DOY) 167) and December solstice (DOY 350) in 2007. Simulation results show successful reproduction of the southern hemisphere MSNA structure including the eastward drift feature of the southern MSNA, which is not reproduced by the default SAMI3 runs using the neutral winds provided by the empirical Horizontal Wind Model 93 (HWM93) neutral wind model. A linear least squares algorithm for extracting tidal components is utilized to examine the major tidal component affecting the variation of southern MSNA. Results show that the standing diurnal oscillation component dominates the vertical neutral wind manifesting as a diurnal eastward wave-1 drift of the southern MSNA in the local time frame. We also find that the stationary planetary wave-1 component of vertical neutral wind can cause diurnal variation of the summer nighttime electron density enhancement around the midlatitude ionosphere.