電離層散塊E層層狀不規則體日夜特性分析

Analyzing of daytime and night time layer typed sporadic E plasma irregularities

葉力揚(Li-yang Yeh)

指導教授 ： 朱延祥

國立中央大學/地球科學學院/太空科學研究所/碩士(2012年)

摘要

本次實驗利用2008年1月28日、2月5日、8月19日及2009年2月26日、3月1日等五天，散塊E層公尺級場沿不規則體回波，針對白天、晚上平均都卜勒速度、頻譜寬、最大訊雜比及層狀結構不規則體東西向寬度、厚度、平均高度及trace velocity做定量的統計分析。其中，白天由於導電性高，使得極化電場容易被短路；相較於白天背景環境，晚上因導電性低，發生較大的極化電場機率相對提高，易使得電子濃度梯度加大，不規則體容易產生較大的擾動。且由實驗結果可知晚上平均都卜勒速度、trace velocity及最大訊雜比都比白天大而進一步的獲得驗證。並且利用頻譜寬出現的範圍，證明中壢雷達觀測到的不規則體都屬於3公尺級的不規則體。另外由分析結果得到白天的層狀不規則體其厚度較厚，東西方向的延伸較窄，平均高度集中於96~99公里處，且高度隨時間的變化呈一波動形式，而晚上層狀結構平均高度略高，於102公里處一分層的現象，且平均高度較高處會有一較快的下降速度。最後利用平均都卜勒速度在高度上的分布，可以推測中性風場其風切的特性，發現當有較大的風切時，會得到較大的頻譜寬及較大的回波功率。

關鍵字

追蹤速度 ； 訊雜比 ； 頻譜寬 ； 都卜勒速度 ； 白天晚上 ； 散塊E層 ； 平均高度

並列摘要

The Chung-Li VHF radar station observed the 3-meter filed aligned irregularities of sporadic E on January 28,2008, February 5,2008, August 18,2008, February 26,2008, and March 1, 2009. We analyzed the mean Doppler velocity, spectral width, maximum SNR, zonal extent, thickness, mean height and trace velocity during the day time and night time, respectively. The conductivity at the daytime is higher than that at the nighttime, and as a result, the polarization of electric field is more liable to be cut off during the daytime. Therefore, the polarization of electric field at the nighttime is increased than that at the daytime, which, in turn, gradient of electron density is increased and irregularities produce a greater vibration. Further, based on our data, mean Doppler velocity, trace velocity, and maximal SNR detected at the nighttime are all increased compared with those obtained at the daytime, as anticipated. By means of the range of spectral width, we demonstrated that the irregularities observed at the Chung-Li VHF radar station is of 3-meter irregularities. In addition, our data indicated that the thickness of layer- typed irregularities at the daytime is increased than that at the nighttime; whereas zonal extent at the daytime is narrowed than that at the nighttime. The mean height is located around 96-99km. The mean height of layer -typed irregularities detected at the nighttime is slightly increased than that at the daytime. Notably, there are two peaks which is separated at the height of 102km. Further, the descending rate of the irregularities is increased when at the higher height compared with that at the lower height. Finally, by means of mean Doppler velocity distributed at the various height, we can estimate the character of wind- shear slope which demonstrated that the magnitude of wind-shear slope is largely in parallel with spectral width and SNR

並列關鍵字

SNR ； spectral width ； doppler velocity ； nighttime ； daytime ； Sporadic E ； trace velocity ； mean height

參考文獻

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