太陽閃焰硬X射線與微波觀測結合雙注入電子群之非熱輻射模擬研究;Hard X-ray and Microwave Non-thermal Emissions from Double Injection Electron Sources during a Solar Flare

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題名:	太陽閃焰硬X射線與微波觀測結合雙注入電子群之非熱輻射模擬研究;Hard X-ray and Microwave Non-thermal Emissions from Double Injection Electron Sources during a Solar Flare
作者:	劉宇倫;Liou, Yu-Lun
貢獻者:	太空科學研究所
關鍵詞:	太陽;閃焰;硬X射線;微波;非熱輻射;Solar;Flare;Hard X-ray;Microwave;Non-thermal Emission
日期:	2018-06-29
上傳時間:	2018-08-31 11:34:11 (UTC+8)
出版者:	國立中央大學
摘要:	太陽閃焰觀測中，硬X射線與微波之非熱輻射通常來自於高能電子的加速。本論文利用RHESSI與Nobeyama觀測站針對2014年9月23日所發生的太陽閃焰事件進行觀測與分析，並結合Fokker-Planck方程式以了解高能電子於閃焰發生時的能量分佈與變化。在RHESSI觀測中，硬X射線的輻射源位於閃焰環形結構的雙足點，而其時間變化則表現短時間的劇變。這些結果顯示硬X射線主要來自於加速的沉降電子所造成。而在Nobeyama之觀測中，微波源位於環形結構的環頂，且其時間變化在抵達峰值後則呈現緩慢遞減的趨勢。除此之外，微波峰值的時間相較於硬X射線，延遲了將近20秒之久。可推測微波輻射主要來自於環形磁場中的束縛電子。且在光譜的分析當中，雖然硬X射線與微波光譜指數於時間上皆是Soft-Hard-Harder (SHH)之變化，然而由微波推得之電子光譜指數δ_m總是小於硬X射線所推得的光譜指數δ_x。且在峰值時間的δ_m與δ_x相差3.7。這些現象解釋閃焰爆發時所產生的加速電子擁有不相同的能量分佈。在Fokker-Planck方程式的計算當中，我們以單冪律分佈模擬擁有相同能量分佈的注入電子，以及以雙冪律模擬擁有不同能量分佈的注入電子，藉以討論兩者不同情況下的結果，並與實際觀測做比較。研究結果中發現，以雙冪律為能量分佈的注入電子所計算的結果在光譜、輻射光變曲線中與觀測上的特徵皆有所吻合。此一結果印證2014年9月23日發生之太陽閃焰事件，其爆發所產生的加速電子擁有不同的能量分佈。 ;The accelerated electrons during the impulsive phase of solar flares are commonly believed to be responsible for the non-thermal emissions in hard X-ray and microwave observations. In this study, we analyze an M2.3 flare on 2014 September 23 by combining the RHESSI and Nobeyama measurements. The non-thermal emissions in HXRs present two chromospheric footpoints, which their time profiles vary with impulsive peaks, showing that precipitating electrons are dominated in this wavelength. For microwaves, the emission burst come from the looptop, and their time variations perform extended tail after microwave peak. As well, the peak time of 17 GHz microwave was postponed by nearly 20 seconds with respect to 20-30 keV HXR peak. Those outcomes indicate microwave emissions are coming from the trapped electrons. In the spectrum analysis, the electron spectral indices δ_m derived from microwaves are always harder than these δ_x derived from HXRs. And, there is 3.7 difference between δ_m and δ_x at peak time. We suggest that the injection electrons from the acceleration region during the flare have multiple energy distribution. Furthermore, we verify those observations by solving the spatially homogeneous Fokker-Planck equation, which was used in Minoshima (2008). We simultaneously calculate numerical results with single and double injection electron sources, which were respectively described by the mathematical forms of single and broken power-law distribution in energy space. We found the calculated light curves and spectra from numerical outputs in both wavelengths are consistent with the observational results. The correspondence agrees with the statement that the acceleration electrons have different energy distribution during the flare on 2014 September 23.
顯示於類別:	[太空科學研究所 ] 博碩士論文

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