IRIS Mg II譜線之太陽閃焰色球加熱現象研究;Investigation of chromospheric heating in solar flares by IRIS Mg II lines

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Title:	IRIS Mg II譜線之太陽閃焰色球加熱現象研究;Investigation of chromospheric heating in solar flares by IRIS Mg II lines
Authors:	陳煜;Chen, Yu
Contributors:	太空科學研究所
Keywords:	IRIS;太陽閃焰;Mg II譜線;色球加熱;IRIS;Mg II
Date:	2018-10-01
Issue Date:	2019-04-02 14:20:20 (UTC+8)
Publisher:	國立中央大學
Abstract:	色球蒸散為伴隨太陽閃焰產生的現象，一般認為閃焰產生的非熱電子撞擊至色球層時，除了會在磁管足部附近輻射出硬X射線之外，過程中也會加熱周遭的電漿，造成局部區域的熱電漿沿著磁場向下運動並有接續的色球蒸散發生。因此利用對應於色球層電漿的IRIS Mg II譜線資料，結合GOES軟X射線與RHESSI硬X射線光變曲線，將能更進一步瞭解色球蒸散現象，希望能推知閃焰的能量釋放情形。本篇論文研究三個閃焰事件，分別為：2014年10月27日爆發於活躍區12192的M1.7 閃焰、2014年11月9日爆發於活躍區12205的M2.3閃焰、2014年10月27日爆發於活躍區12192的X2.0閃焰，分析各事件的Mg II三種發射譜線(即Mg 2791.6 Å、 Mg II k、Mg II h)的特徵，尤其因為其中的2791.6 Å譜線對於閃焰發生的時間點非常敏感，其光強增加的時間往往能對應於硬X射線的增強，又因為該譜線的譜形比起Mg II k與Mg II h單純，因此特別針對2791.6 Å再進一步估算該譜線之各項物理參數(如溫度、線寬、都卜勒速度等)。我們的結果發現，在閃焰初期的主要能量釋放階段，2791.6 Å譜線有短暫、明顯的線寬變寬、紅移速度增加的現象，速度峰值約介於6至18 km/s，而溫度的時變曲線則較為多變。另外，我們也觀察到不同區域的譜線特徵會有所差異，可能代表不同的物理圖像。;Chromospheric evaporation is usually accompanied by the occurrence of solar flares. Generally, the flare-produced non-thermal electrons impact the chromosphere and heat the ambient plasma, resulting in the downward motion of thermal plasma and the subsequent chromospheric evaporation. Therefore, it is helpful to understand the physical meaning of chromospheric evaporation and the energy release process in solar flares by combining the IRIS Mg II data with the GOES soft X-ray and RHESSI hard X-ray light curves. Three flare events are investigated in this study, which are the M1.7 flare on 2014 October 27 at AR 12192, the M2.3 flare on 2014 November 9 at AR 12205, and the X2.0 flare on 2014 October 27 at AR 12192. We analyze the lightcurves of three Mg II lines (i.e., Mg 2791.6 Å, Mg II k, and Mg II h) in specific areas of each event. Moreover, since the 2791.6 line is sensitive to the heating of the lower chromosphere, responses correspondingly to the increase of hard X-ray emissions, and has a simpler spectral shape than that of Mg II k and h lines, we particularly estimate the spectral quantities of temperature, line width, and Doppler velocity from the 2791.6 line. We find that in the early impulsive phase, the red-shift velocity increases obviously and shortly with the peak value between 6 km/s and 18 km/s, as well as the broadening of line width. But the profile of temperature evolution is variable at each area. The spectral properties are observed to be different at different regions, which may indicate different physical pictures.
Appears in Collections:	[Graduate Institute of Space Science] Department of Earth Sciences

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