利用ROCSAT-1和DMSP衛星資料研究磁暴時中緯度重離子異常現象

A Study of Mid-latitude Heavy Ion Anomaly Using ROSAT-1 and DMSP Data

范純彬(Chun-pin Fan)

指導教授 ： 葉惠卿

國立中央大學/地球科學學院/太空科學研究所/碩士(2007年)

摘要

本文利用ROCSAT-1和DMSP F-13的SSJ/4衛星資料，研究頂部電離層重離子(主要是NO+ )含量異常的現象與發生機制。我們挑選在2003年11月20日發生的巨型磁暴期間所觀測到的離子異常事件作為探討對象。因此，本篇論文主要是探討距地表上空600公里處，中低緯度電離層F層NO+ 重離子密度含量的異常現象 (此時所觀測到NO+、離子密度佔全離子密度5%以上。平時在地表上空600公里處，N2+、NO+ 及O2+ 等重離子的含量幾乎不可能超過1%)。我們分析ROCSAT-1中IPEI觀測資料包括離子濃度、水平速度及衛星軌道資料，發現NO+ 重離子含量的異常現象的地方時間LT 04:00 ~10:00、磁緯度40度~50度等相關訊息，而且由分析離子速度資料可知道重離子異常區的離子是向西及赤道方向流動。這些有NO+ 百分比含量異常的地方均對應溫度提升且位在近極光區的低緯度邊界，該區是向東(高緯)及向西(中緯)電漿流動交匯的地方，而這些觀測到之高含量大區域的NO+ 離子異常現象的成因，可能是正值磁暴期間，高緯度極光區所產生的大量NO+ 離子熱脹上升，爾後這些高緯度來的NO+ 離子受到副極光區極化電漿流(SAPS)電場的牽動向西也向中緯度傳播，而被ROCSAT-1在距發源地附近觀測到。

關鍵字

磁暴

並列摘要

Data from ROCSAT-1 and DMSP F-13 SSJ/4 satellite are used to study the phenomena of the anomalous increase of heavy ions (mainly NO+) in the topside ionosphere. We focus on the unusual events of NO+ anomaly observed during the magnetic storm on 20 November 2003 for detailed analyses. At 600 km altitude, ROCSAT-1 normally observed the percentage content of NO+ to be less than 1% in the mid-latitude ionosphere under geo-magnetically quiet conditions. However, ROCSAT-1 did observe high percentage (> 5%) of NO+ spanned large portions of at least three satellite paths during the November 2003 storm. We analyze ROCSAT-1 IPEI data including ion density, velocity and temperature as well as the SSJ/4 particle data from DMSP for these NO+ events. We found that these events occurred in the magnetic local time sector of 04:00~10:00 LT and in the magnetic latitude range of 40 to 50 degrees, which were close to the precipitating ion equatorward boundaries. In addition, these events were found in the temperature enhanced regions. Moreover, the ion velocity data revealed that the ion flows moved toward west and toward lower latitudes. Based on these characteristics we infer that the heavy ions may originate from the sub-auroral latitudes (source region), where these heavy ions were driven by the poleward sub-auroral electric fields to drift westward and moved equator-ward to the lower mid-latitudes. ROCSAT-1 was nearby the source regions to observe the NO+ anomaly events.

並列關鍵字

heavy ions ； NO+

參考文獻

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