太阳大气中激波与冕环相互作用的研究

Shock wave is one of the most important concomitant phenomena of the eruptions of solar flares or CMEs (coronal mass ejections). During the eruption of solar flares, they release a great quantity of energy and eject a great deal of mass with high velocity in a few minutes. At the same time, many other phenomena, such as oscillations of coronal loop, CMEs and filament eruption, accompanied with the solar flares are often visible in different wavelength. The erupted filaments or CMEs run away from the center of the solar flare with a very high velocity of several hundred km/s. The velocity normally exceed sonic velocity that the filaments compress the coronal plasma and may trigger shock waves in the corona. By using the data of high spatial and time resolution observed by Solar Dynamics Observatory (SDO) launched three years ago, we will do some basic researches on the interactions between shock waves and coronal loop oscillations: (1) explore the formation mechanism of shock waves in the solar atmosphere and exact measure the physical parameters of the shock wave, such as propagation velocity, intensity; (2) exact measure the physical parameters of the coronal loop oscillations driven by shock waves, such as variation period, oscillation amplitude, initial velocity, damping coefficient; (3) On the basis of the propagation velocity of the shock waves and initial oscillation velocity of the coronal loops measured in the former two steps, we will calculate the ratio of the mass of the shock waves to the mass of the coronal loop, Ms/Mc, by using the momentum conservation equation. And then investigate the physical parameters of the shock waves, such as thickness and intensity, and the physical parameters of coronal loops, such as volume and density. Furthermore, we investigate the process of the coronal loops heated by shock waves and look for the evidences to prove the heating process.

激波是耀斑或CMEs爆发中出现的一种重要伴随现象。耀斑爆发时会在短时间释放大量能量和抛射大量高速物质。同时，诸如冕环振荡、CMEs、暗条爆发等伴随现象经常在不同波段被观测到。爆发暗条或CMEs通常以数百km/s的速度从耀斑附近逃离。这些超声速物质会强烈压缩等离子体而产生激波。利用SDO采集的高质量数据，我们针对激波与冕环的相互作用开展以下研究：（1）探索太阳大气中激波形成机制，并精确测定激波物理参数，如速度、强度。（２）精确测量激波驱动的冕环振荡的物理参数，如周期，振动幅度，振荡速度、阻尼系数等。（３）基于已测定的激波速度和冕环受冲击后的振荡速度，利用动量守恒计算参与碰撞的激波层内的等离子体质量Ms和冕环内等离子质量Mc的质量比Ms/Mc。在此基础上探索激波层厚度、密度以及冕环的体积和密度等的分布特征。进而利用能量守恒估算冕环在受冲击后可能升高的温度，并用观测数据验证激波加热冕环的过程。

研究工作主要针对太阳大气中的激波现象、冕环振荡、黑子振荡、太阳大气行波所展开。SDO是研究激波/日冕波的强力工具，运用SDO观测的高分辨率数据研究CME爆发过程过程中出现的日冕波表明日冕波极有可能是由CME、而不是耀斑所驱动形成。另外，利用NVST观测的高分辨率数据研究了黑子中太阳大气行波，结果发现，三分钟振荡和五分钟振荡可能是由同一种形成于黑子本影区的大气行波所产生，但在亮度变化上表现出不同周期。针对激波冲击冕环引起后者做周期性振荡的现象，运用结构力学相关知识，推导出了冕环振荡周期与环长、磁场强度、等离子体密度之间的关系等，该关系为研究冕环运动特征、结构特征提供一条可行途径。这些工作经过整理后，发表在国内外的学术期刊上，发表论文共计六篇。培养和招收硕士生8名，其中4名已经取得硕士学位，4名在读。