福衛三號S4閃爍指數時空變化與潮汐分析;Spatial-Temporal Variation and Tidal Analysis of the FORMOSAT-3/COSMIC S4 Scintillation Index

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Title:	福衛三號S4閃爍指數時空變化與潮汐分析;Spatial-Temporal Variation and Tidal Analysis of the FORMOSAT-3/COSMIC S4 Scintillation Index
Authors:	邱珮芸;Chiu, Pei-Yun
Contributors:	太空科學研究所
Keywords:	閃爍;Scintillation
Date:	2018-01-26
Issue Date:	2018-04-13 10:49:56 (UTC+8)
Publisher:	國立中央大學
Abstract:	低層大氣層所產生的重力波、行星波、大氣潮汐等大氣擾動會向上傳遞,造成電離層電漿擾動,近年來提出此低層大氣層與電離層間耦合之相關證據以及機制的研究也逐漸增加。福爾摩沙衛星三號 (FORMOSAT-3/COSMIC)採用掩星(radio occultation)技術,其觀測涵蓋範圍以及解析度可以提供多年全球與全天的大氣層以及電離層垂直分佈資料。由於福衛三號 S4 閃爍指數(scintillation index)時空分佈與電離層中散塊 E 層(sporadic-E)、F 層不規則體(spread-F)相似,本篇論文利用 2007 年到 2014 年的 S4 閃爍指數來探討電離層擾動受到低層大氣影響的可能因素, 並期望可應用於全球衛星通訊干擾、定位等之分析。為了探討低層大氣層現象對電離層造成擾動的來源,我們將 S4 閃爍指數,與量化大氣層聖嬰-南方震盪現象(El-Niño Southern Oscillation)指數之一的海洋聖嬰指數(Oceanic Niño Index)以及對流層高度進行比較分析, S4 閃爍指數大小與海洋聖嬰指數呈現相似的長期趨勢,其相關係數達到 0.5 左右,且兩者在小波分析(wavelet analysis)頻譜中也都呈現出約 1.5 年與 2.5 年左右的週期,由於低層大氣擾動向上傳遞的過程中會受到許多不同機制影響,可合理推測大氣層聖嬰-南方震盪現象極有可能為調幅(modulation) 電離層散塊 E 層(Sporadic-E)的低層大氣擾動之一;同時,我們也針對 S4 閃爍指數進行潮汐分析,並利用較大的分潮重建全球 S4 閃爍指數在不同太陽活動週期的時空分佈,以了解不同大氣潮汐分潮對電離層擾動的影響。;The tides generated from the lower atmosphere can propagate upwards, causing ionospheric perturbations. Many studies have shown evidence for several types of atmosphere-ionosphere coupling in recent years. By using GPS radio occultation (RO) signals, FORMOSAT-3/COSMIC satellites can provide global morphology of the S4 scintillation index, quantifying the distribution of GPS and satellite communications disruptions. In this study, we show the possible relation between Sporadic-E (Es) and El-Niño Southern Oscillation (ENSO) by using the FORMOSAT-3/COSMIC S4 scintillation index, Oceanic Niño Index (ONI) and tropopause height from 2007 to 2014. The long-term variation of S4 index anomaly with 3-month running mean and solar activity de-trended in the E-region shows similar trend and periods in wavelet spectrum to ENSO and tropopause height. These results indicate that ENSO signatures can be transmitted to Es formation mechanisms, potentially through modulation of vertically propagating atmospheric tides that alter lower thermospheric wind shears. We also analyze the local time and spatial variation of the COSMIC S4 index, and quantify the major variation modes through tidal analysis from 2007 to 2014. The seasonal variations of the S4 index are presented in this method and the tidal signatures examined, to determine their distribution and overall effect on ionospheric scintillation. The global S4 index longitudinal and local time distribution is reconstructed using the results of our tidal analysis during solar minimum year (2009) and solar maximum year (2014), to determine the significance of zonal irregularities resulting from tidal disturbances.
Appears in Collections:	[Graduate Institute of Space Science] Department of Earth Sciences

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