冕环中扭转Alfvén波和快波的耦合共振  

ALFVEN WAVE AND FAST WAVE COUPLING RESONANCE IN CORONAL LOOPS

作　　者：叶占银[1] 魏奉思[1] 王赤[1] 冯学尚[1] 罗庆宇[1] 

机构地区：[1]中国科学院空间科学与应用研究中心,北京100080

出　　处：《空间科学学报》2004年第6期401-411,共11页Chinese Journal of Space Science

基　　金：国家自然科学基金资助项目(40104008;49990450;49990452;40204009)

摘　　要：推广完备正交函数系(OFSE)展开方法,应用它研究冕环中无耗散扭转Alfven波和快波耦合的时变过程.采用这种方法,从数学上描述了总体波模的固有角频率,从理论和数值计算结果两方面分析了Alfven波和快波耦合时冕环中磁力线Alfven波固有角频率.采用这种方法,分析了耦合驱动项和Alfven波共振的关系.计算结果给出了耦合共振出现位置Alfven波和快波的波幅特征,发现如果足点驱动角频率不等于冕环总体波模的固有角频率,在耦合共振位置当扭转Alfven波幅出现δ断面时,快波振幅沿径向梯度很大,有时近似为一个间断,非常有利于快波耗散;如果足点驱动角频率等于总有体波模的固有角频率,Alfvn波振幅出现δ断面时在径向出现丰富的小尺度结构,共振位置近似为一个间断,非常有利于Alfven波耗散.Complete Orthogonal Function Series Expansion (OFSE) method is generalized and applied to make research about the time evolution coupling process of fast and Alfven waves in coronal loops. With the OFSE method, intrinsic angular frequencies of coronal loop quasi-modes could be described mathematically and the intrinsic angular frequency of torsional Alfven waves in every magnetic field line of coronal loops is investigated theoretically and numerically. With the method, the relationship between a coupling driven term and torsional Alfven wave resonance is analyzed. Numerical result presents wave amplitude features at the coupling resonant place. It is found that: when the footpoint driven angular frequency is not equal to one of quasi-mode intrinsic angular frequencies, at the resonant position with a δ profile of Alfven wave amplitude, absolute value of radial gradient of fast wave amplitude is very large and approximates a discontinuity, which is necessary to dissipate fast waves. On the other hand, if the footpoint driven angular frequency is equal to one of quasi-mode intrinsic angular frequencies, widespread small scale structure of Alfven wave amplitude and an approximate discontinuity at resonant plece, which are necessary to dissipate Alfven waves, appear.

关 键 词：角频率 近似 间断 耗散 数系 共振 耦合 波幅 扭转 位置 

分 类 号：P182.62[天文地球—天文学]