多波段观测超新星遗迹激波结构研究宇宙线的有效加速

Supernova remnants (SNRs) have been accepted as the best origin candidate of Galactic cosmic rays (GCRs) . Currently, the key in GCRs origin study is to prove that the main component of CRs, protons, are also accelerated effectively by SNRs as what have happened to electrons. One of the valid methods to search high energy protons is the sub-GeV and above 100 TeV observation. However the relevant studies are still restricted due to the poor sensitivity of current observation instruments. Another method is to investigate the shock structure variations caused by CRs. That is the arising of a precursor in the front of the shock discontinuity where the upstream materials are heated up and decelerated before across the shock front. Our project will focus on three observational phenomena from the shock structure variations which are 1) colder post shock temperature; 2) narrower contact discontinuity; 3) concave spectra, based on multiwavelength data. A detailed study will point to SNR Kepler to build the relationship between effective CRs acceleration and magnetic field, shock speed, SNR's evoltion stage, density of surrounding medium and so on. Futhermore, we will seek the evidence of concave spectra from a large SNRs sample and perform statistical study.

超新星遗迹（SNRs）已被广泛接受为银河宇宙线（GCRs）起源的最好候选体。当前GCRs起源研究的关键在于证明SNRs在有效加速电子的同时，对CRs的主要成分，质子的加速也是有效的。在sub-GeV和100TeV以上能段的观测是寻找高能质子的有效方法之一。但受到观测设备灵敏度的限制，相关研究目前仍然进展有限。另外一个示踪SNRs中质子有效加速的方法是研究CRs对激波结构的改变，即激波间断面前出现一个先驱结构，上游物质在先驱中被提前加热和减速。本项目将通过多波段数据研究激波结构改变带来的3个可观测效应：1）更冷的激波后温度；2）更窄的接触间断面；3）“凹”型同步辐射谱。 以此为依据研究SNR Kepler中CRs有效加速与磁场，激波速度，SNRs演化阶段，周围介质密度等参量之间的关系。 并在更大的SNRs样本中寻找“凹”型同步辐射谱，开展统计研究。

激波与星际介质相互作用过程中存在着丰富的物理现象，包括宇宙线的加速，从射电到伽马射线的全波段辐射等等。这些过程除了可以用来研究超新星遗迹本身的物理性质之外，还可以使超新星遗迹作为探针研究星际介质的性质。本项目通过多波段数据分析以及数值模拟方法，研究了宇宙线中重元素的加速和银河系星际介质的性质。我们发现：1）激波中重元素从尘埃中剥离出来的效率要高于理论值。2）以超新星遗迹为探针得到的银河系气体柱密度-尘埃消光比率基本是一个常数，它不随星际介质的空间位置和物理性质变化而变化。3）通过数值模拟我们找到了W51C“消失”的半个壳层。4）以红团簇星为标准烛光，利用的超新星遗迹的消光特征，我们系统地测量了银河系第一和第四象限内超新星遗迹的距离。