| 摘要: | 太陽高能質子的產生現已知道與太陽爆發現象或是行星際空間結構加速而來，例如：太陽閃焰、日冕物質拋射、電漿噴流和行星際震波、共轉交互作用區 (corotat-ing interaction region, CIR) 造成的粒子加速。本篇論文藉由分析日地關係天文台(Solar Terrestrial Relations Observatory, STEREO)的高能質子通量資料，並結合現地量測的太陽風電漿資料、行星際磁場以及極紫外線太陽影像，藉此找出高能質子通量的時變曲線、能譜特性與行星際震波、太陽磁重聯現象之間的關聯性。
本篇論文將STEREO衛星在2011年到2014年之間觀測到的太陽高能質子事件，根據加速源的不同分類成：(1)單一磁重聯加速、(2)多個磁重聯加速、(3)多個激震波加速、(4)先磁重聯後激震波加速、以及(5)行星際壓縮區。分析結果顯示出在磁重聯現象發生之後約一個小時左右，在質子通量上觀察到明顯陡升，到達峰值之後緩慢的下降，且越高能的質子通量越早開始上升、越早到達峰值且越早下降到背景值，高能量段(>10 MeV)的質子通量反應比低能量段(<10 MeV)的還要明顯。而全部39個行星際震波在經過衛星時，在質子通量上會有以下三種反應：(a)所有能量段的質子通量都有上升、(b)只有低能量段的質子通量有上升、(c)所有能量段的質子通量都沒有變化，低能量段有上升的事件有32個而高能量段有上升的只有17個事件，這顯示出行星際震波對低能量段的質子加速比較有效。而質子通量在行星際震波到達之前會緩慢上升，在震波到達衛星時會有明顯的峰值，而在震波遠離衛星時緩慢的下降。
另一方面，本篇論文利用Band et al. (1993)的擬合伽瑪射線的方程式，來擬合每個太陽高能質子事件的能譜，並統計分析每個事件的能譜參數。分析結果發現，單一、多個磁重聯加速事件的高能量段能譜指數較小，而低能量段並沒有特定的分布趨勢。多個激震波加速事件的低能量段能譜指數較大，而高能量段並無特定的分布趨勢。上述兩點顯示出行星際震波對低能量段的質子加速較有影響，而磁重聯對高能量段的質子加速較有影響。另外，先磁重聯後激震波加速事件的???幾乎都落在8-40 MeV之間。;Solar energetic particles (SEPs) are accelerated by solar eruption, e.g., solar flare, cor-onal mass ejection (CME), and plasma jet, or by interplanetary structures, e.g., interplanetary shock (IP shock) and corotating interaction region (CIR). In this study, we would like to char-acterize the light curve of energetic proton flux and spectral parameters, and to find out the associations with shocks and magnetic reconnections by combining the proton flux data with the in situ solar wind data and extreme ultraviolet (EUV) images from Solar Terrestrial Rela-tions Observatory (STEREO) satellite.
We classify the solar proton events (SPEs) observed by STEREO from 2011 to 2014 into five types, including (1) single magnetic reconnection acceleration, (2) multiple mag-netic reconnection acceleration, (3) multiple shock acceleration, (4) magnetic reconnection and shock acceleration, and (5) interplanetary compression region. Our result shows that high-energy (>1 MeV) proton flux increase obviously about an hour after magnetic reconnec-tion occured. Moreover, proton fluxes at higher energies start to increase, reach the peak, and back to the background value earlier than those at low energies. High-energy protons have more obvious response to the magnetic reconnection acceleration than low-energy (<1 MeV). Three following response are seen in the proton light curves when an IP shock passing through the satellite, i.e., (a) flux increase in all energies, (b) flux increase in low-energy pro-tons, and (c) no flux changes. Low-energy protons have more obvious response to the IP shock acceleration than high-energy protons.
In addition, we analyze spectral parameters in all SPEs using the gamma ray fitting function providing by Band et al. (1993). Our results show that the events accelerated by sin-gle and multiple magnetic reconnection have smaller power law index at high energies but no preference is found at low energies. The multiple shock acceleration events have larger power law index at low energies but no preference at high energies. It is suggested that protons can be accelerated to a few tens of MeV or even a few hundreds of MeV by magnetic reconnec-tion. The ??? (energy break) for the events of magnetic reconnection and then shock accelera-tion is found to be in the range of 8-40 MeV. |
