全球電離層散塊E層特性之研究：風切理論的探討; Climatology of ionospheric Sporadic E Layer : Examination of Wind Shear Theory

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Title:	全球電離層散塊E層特性之研究：風切理論的探討;Climatology of ionospheric Sporadic E Layer : Examination of Wind Shear Theory
Authors:	陳冠廷;Chen,Kuan-Ting
Contributors:	太空科學研究所
Keywords:	散塊E層;風切理論;Sporadic E;wind shear theory
Date:	2013-07-22
Issue Date:	2013-08-22 11:41:29 (UTC+8)
Publisher:	國立中央大學
Abstract:	本篇論文利用風切理論作為理論基礎來描述離子在高度上的輻合機制，在研究過程中加入鐵離子；因此在探討散塊E 層的形成時，有了在背景環境中存在讓離子輻合的機制(機制項)，又有了組成散塊E 層最主要的金屬離子在空間中分布的資訊(源項)，使得對於電離層散塊E 層的模擬更加完整。在模擬的過程當中，利用HWM-07 水平風場模型、IGRF 地磁場模型、MSIS-00 模型來獲得描述離子垂直飄移速度所需要的背景環境參數；並且利用WACCM 模型獲得鐵離子濃度全球分布資料，進而可模擬離子垂直通量的大小。接著即可以對散塊E 層在季節變化造成的南北半球不對稱性、空間中的分布特性以及日變化的這些特性進行模擬。接著利用福衛三號電波掩星法所觀測到的電離層散塊E 層，分析統計後獲得散塊E 層的季節變化、經緯度分布及日變化這些特性與分析模擬結果獲得的散塊 E 層特性進行驗證與比較。研究內容顯示，模擬結果與福爾摩沙衛星三號觀測結果在水平面上大致.吻合；並且在模擬散塊E 層特性的研究內容中，可進一步的證明其散塊E 層發生機率在不同季節的南北半球的不對稱性與風切效應有關。 On the basis of GPS radio occultation (RO) technique, we develop a method to extract ionospheric sporadic E (Es) layer from COSMIC-measured ionospheric data (e.g., GPS signal signal-to-noise ratio, L1 and L2 excess phases and RO-retrieved electron density) to investigate the climatology of the Sporadic E layer. The results show that there is salient summer-winter asymmetry in the occurrence rate of the Es layer, namely, higher in summer hemisphere and lower in winter hemisphere. In addition, there is a strong tendency for the Es layer to descend with local time that is in harmony with the diurnal or semi-diurnal tidal motion, depending on season and latitude region. In order to realize the physical process responsible for the climatology of the COSMIC-measured Es layer, we simulate the temporal and global distribution of the occurrence of the Es layer in accordance with wind shear Theory. We calculate vertical ion drift velocity based on empirical models of the ionosphere, including HWM07, MSIS00, IGRF. The ferric ion (Fe+) density calculated from Whole Atmosphere Community Climate Model(WACCM) is used to obtain ferric ion vertical flux. The simulation results show that the seasonal asymmetry of the Sporadic E layer occurrence rate between the summer and winter hemispheres is very likely caused by the neutral wind shear in the Es region.
Appears in Collections:	[Graduate Institute of Space Science] Department of Earth Sciences

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