| 摘要: | 這個論文主要在探討太陽無線電波的源區和其他在太陽急遽爆發(太陽閃焰/日冕噴發事件)後相關聯的無線電波現象
我們使用的觀測資料包含了在太陽閃焰不同爆發相位時的高能X光源區的影像、各頻寬的第三型無線電波爆以及不同波段的超紫外線影像中的微分發射線測量, differential emission measure (DEM))。
我們首先比對各波段的觀測資料庫,包括涵蓋多頻段的無線電波,超紫外線影像(由AIA, Atmospheric Imaging Assembly / Solar Dynamics Observatory所觀測) 和高能X光影像(由RHESSI, Ramaty High Energy Solar Spectroscopic Imager所觀測),在我們的研究中,我們採用這兩項觀測證據(高能X光源區影像與超紫外線噴流)當作偵測的工具。另外,我們也使用微分發射線測量來繁衍太陽閃焰發生區域的日冕溫度,此方法是使用AIA所觀測到不同波段的超紫外線影像中的發射線量值來加以計算的。
在太陽閃焰爆發時,由磁場重聯所激發釋放的電子束往外噴發,傳播至行星際空間後便激發第三型無線電波爆。我們研究結果表示:當第三型無線電波爆,高能X光譜與超紫外線光譜峰值的發生時間幾近同時,便代表此三者有著密不可分的關係, 而由不同能段的高能X光源區與超紫外線噴流的位置顯示激發第三型無線電波爆的電子應該源自於太陽閃焰的高能非熱區。
在微分發射線測量分析中,我們發現在超紫外線噴流與第三型無線電波爆發生前,在磁環足點區會提早增溫的現象(2011-02-15),而重複發生在同個位置的超紫外線噴流事件中,這些增溫現象可能是由閃焰加速粒子穿透至大氣層底層導致或是前一個噴流事件遺留下的
另外,我們在活躍區噴流區的溫度研究中,發現到延著噴流方向分布的不同溫度的碎散結構,這是在SDO觀測裡的首見,也很可能此碎散結構與第三型無線電波爆的產生相關。
另外,在本篇論文中,我們也探討關於激發第二型的無線電波爆的激波強度與電波爆強度的關係。在2011年1月到2012年9月中,我們使用e-Callisto 全球聯網(Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory)的觀測資料,大約有15%的第二型無線電波爆有頻譜分離(band-splitting)的結構產生，而我們的分析顯示一個第二型的無線電波爆產生,其激發波的強度約略要超過快波馬赫數~1.2的數值。
The main theme of this thesis is the investigation on the source region of solar radio bursts and relevant radio emission after solar eruptive activities (flare/CME). Our data analysis concentrated on the hard X-ray (HXR) imaging, Type III radio bursts in the broader frequency range and the differential emission measure (DEM) distribution derived by extreme ultraviolet (EUV) images during the impulsive phase of flares.
First, we match the board-band radio observation data sets and those of AIA (Atmospheric Imaging Assembly/Solar Dynamics Observatory), RHESSI (Ramaty High Energy Solar Spectroscopic Imager) to build a list. We use two observational features – EUV jetting and HXR source, to be the diagnostic tools in our study. And we also use the DEM to determine the coronal temperature in the targeted flaring regions with AIA observations.
The type III radio emission is excited by the outward traveling electron beams from the magnetic reconnection of flare. The near simultaneous occurrences of Type III bursts, HXR and EUV (line 211 ?) peaks speak of a common origin associated with the impulsive flare in our studies. The morphology drawn by the HXR sources at different energies and EUV jets reveals the solar sources of type IIIs-emitting electrons may originate from the HXR non-thermal regions.
In the DEM analysis, we found an early temperature increase at the jet footpoints precedes the onset of the EUV jet and type-III burst in event 15, Feb., 2011. For the multi-occurrences of EUV jets at same position, the early temperature increase is caused by flare-accelerated electrons or from remnant of the previous jet. Our temperature diagnostic in the active region jets shows that complicated fragmental feature of different temperatures along the jet direction, which is first seen in AIA observations. And we believe this fragmental temperature feature is associated with the outward electron beams and the formation of type III bursts.
We also select 21 type II radio burst events and investigate the evolutions of the shock strength and the radio intensity during the lifetime of the bursts. We found that among 139 type II radio burst events observed by e-Callisto network (Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory) from January 2011 to September 2012, only 20 events, i.e. 15%, present band-splitting features in the radio dynamic spectra. Our analysis indicates that most of these bursts appear when the fast-mode Mach number exceeds 1.2. |
