INVESTIGATING THE CONDITIONS OF THE FORMATION OF A TYPE II RADIO BURST ON 2014 JANUARY 8
INVESTIGATING THE CONDITIONS OF THE FORMATION OF A TYPE II RADIO BURST ON 2014 JANUARY 8
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DOI：
10.3847/0004-637x/830/2/70
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发表时间：
2016-09
期刊：
影响因子：
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通讯作者：
W. Su;X. Cheng;M. Ding;P. Chen;Z. Ning;H. Ji
中科院分区：
文献类型：
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作者：
W. Su;X. Cheng;M. Ding;P. Chen;Z. Ning;H. Ji
据信，II型射电暴是由冲击波产生的。为了了解II型射电暴的产生条件，我们分析了一个激波锋面的物理参数。我们选择的II型射电暴是由西伯利亚太阳射电望远镜（SSRT）和Learmonth无线电台观测到的，它与2014年1月8日发生在太阳动力学观测台上的大气成像组件观测到的边缘日冕物质抛射（CME）有关。日冕内CME的演化呈现向外传播的双层结构。我们用一个偏圆拟合结构的外层（OL），并将其分为- 45°至45°的7个方向，角间距为15°。我们沿着七个方向测量了OL速度，发现相对于中心方向- 15°方向的速度最快。我们采用差分发射测量法计算II型射电暴启动瞬间OL处的物理参数，包括温度(T)、发射测量（EM）、温度比（）、压缩比(X)和alfv<s:1>马赫数（MA）。我们将X和MA与无线电频谱中的带分裂量进行了比较，发现这种II型射电暴是在位于45°方向扇形的OL的一个小区域产生的。结果表明，II型射电暴（冲击）的产生需要更大的X和MA值，而不仅仅是更高的干扰速度。
It is believed that type II radio bursts are generated by shock waves. In order to understand the generation conditions of type II radio bursts, we analyze the physical parameters of a shock front. The type II radio burst we selected was observed by the Siberian Solar Radio Telescope (SSRT) and Learmonth radio station and was associated with a limb coronal mass ejection (CME) occurring on 2014 January 8 observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. The evolution of the CME in the inner corona presents a double-layered structure that propagates outward. We fit the outer layer (OL) of the structure with a partial circle and divide it into seven directions from −45° to 45° with an angular separation of 15°. We measure the OL speed along the seven directions and find that the speed in the direction of −15° with respect to the central direction is the fastest. We use the differential emission measure method to calculate the physical parameters at the OL at the moment when the type II radio burst was initiated, including the temperature (T), emission measure (EM), temperature ratio ( ), compression ratio (X), and Alfvén Mach number (MA). We compare the quantities X and MA to those obtained from band-splitting in the radio spectrum, and find that this type II radio burst is generated at a small region of the OL that is located at the sector in the 45° direction. The results suggest that the generation of type II radio bursts (shocks) requires larger values of X and MA rather than simply a higher speed of the disturbance.