電離層中性分子密度變化對太陽活動的響應

Variations of ionospheric neutral densities in response to solar activity

何萬謙(Wan-chien Ho)

指導教授 ： 黃健民

國立中央大學/地球科學學院/太空科學研究所/碩士(2014年)

摘要

本文主要討論太陽活動對410公里高度中性大氣密度的影響。首先，利用太陽的輻射通量F10.7以及EUV兩個波段來對2003年到2008年CHAMP衛星所觀測到410公里的中性大氣密度來做回歸，在做資料分析時，發現大氣密度對太陽輻射的響應是有一個相位延遲，從其他的文獻也發現大氣密度的變化跟太陽輻射的變化會有一個時間延遲；經過分析後，所得到的結論是在2003年到2008年的背景中，延遲的時間約為一天。再來，比較使用不同多項式所回歸出的結果，從這些結果可以發現在這段時間內不同多項式所回歸出來的結果差異不大，單一參數的多項式不會比多個參數的多項式來的差。且EUV的資料，並不像F10.7來的完整，所以本文主要利用F10.7來進行此研究。

利用太陽輻射回歸出來的結果再與原始的資料做比較後，會發現有不小的差異。這個差異的部分在靠近太陽極小期附近是與地磁擾動有較高關連性，所以在差異的部分再利用Kp來做線性回歸。研究發現在太陽較活躍的時期太陽輻射對大氣的影響是較高的，但是在太陽較安靜的時期，就變成以太陽風所引發的地磁擾動變成影響高層大氣密度變化的主要因素。最後發現回歸出的資料與原始資料差異的部分，有一個大約130天左右的成份，並發現誤差原因來自於衛星本身軌道面的當地時間，而將這個成分去除掉後，回歸出來的資料與原始資料的相關係數可以高達0.95，而且這個因素在太陽極小期附近的影響是比較大的。

關鍵字

電離層 ； 太陽 ； 中性大氣

並列摘要

This thesis focuses on the studies of variations of neutral densities at a height of 410 Km in response to solar activity. It use solar radiation indices F10.7 and EUV to linearly fit neutral density measured by the Challenging Minisatellite Payload (CHAMP) satelliteduring the period 2003 - 2008.

Aclearly phase delay in solar radiation and neutral density have been found when we were doing data analysis. It's also pointed out that neutral density variation has a time delay with solar radiation in the previous papers. In this study, we could get a conclusion that the time delay is one day during 2003 to 2008.

In doing the linear regression,the result from multiple parameters is almost the same as that from single parameter. And, because of the more completeness of the observations of F10.7 than EUV, we decide to use F10.7 index to be the main parameter in the following studies.

To compare original data of neutral density with the fitted data has a significant difference in the period of low solar activity. The difference has high relation with Kp index. Additional linear regression is required for these differences with Kp index.The results indicate that solar radiation is a dominate factor in the variations of neutral densities in the period of high solar activity, and geomagnetic activity produced by the solar wind becomes important in the low solar activity.

The difference between original data of neutral density with the fitted data has a period of 130 days, which can be attributed to the satellite orbit.Removement of this component can increase the correlation coefficient of the original data the fitted data up to 0.95. But this effect is only important in the period near solar minimum.

參考文獻

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