磁场中p模/s模的转换及黑子对声波的吸收

在柱坐标下将黑子周围的环形区域（黑子除外）内的振荡分解为朝向黑子传播的（入射的）波和离开黑子传播的（出射的）波。对无黑子的环形区域内的振荡也进行了同样的分解。将黑子周围的入射波看成是被黑子磁流管磁化了的介质（介质内的磁场基本是水平的）中的波。而无黑子区的入射波看成是非磁化介质中的波。比较这两种波在固定波数下功率随频率的分布发现，在磁化介质中不同径向除ｎ的声波（ｐ模）频率系统降低，同时功率也降低，降低的功率最高达非磁化介质中波的功率的３０％。而比较在固定频率下功率随波数的分布发现，磁场中ｆ模及ｎ＝１，２，３的ｐ模的脊向高波数方向位移，功率的降低受频率调制，即声波在某些有限的频带中被吸收。这些观测表明，在磁场中ｐ模与磁声重力波（ＭＡＧ）产生了模式混合或耦合。模式混合的存在支持了模式转换作为ｐ模式被黑子吸收的机制的解释。此外，本文还分析了转换的ＭＡＧ波进入黑子磁流管（其中的磁场基本上是垂直的）后进一步被吸收，吸收的功率最高达ＭＡＧ波的２０％。在磁流管内没有进一步观测到模式的转换

The Observations of p -Modes/ s -Modes conversion in the Magnetic Field and Absorption of p -Mode by the Sunspot

We decomposed the oscillations inside the annular region surrounding a spot (excluding the spot itself) into the incoming waves(propagate towards the spot)and the outgoing waves(away from the spot)under a cylindrical coordinate system.We make the same decomposition for the oscillations in the annular region surrounding the spotless area.The incoming waves in the region surrounding the spot can be considered as ones,which propagate inside the medium magnetized by the spot flux tube (the magnetic fields in the medium are basically the horizontal)and the incoming waves in the spotless region are considered as the waves propagating inside the non-magnetic medium.By comparing the distributions of the power with the frequency for the two kinds of waves in fixed wave-numbers,it can be found that the frequences,at which the ridges of mode are placed,have been reduced systematically for different radial order n of the mode in the magnetic field,and the power of the waves in the magnetic feild has been reduced as well.The reduced power of the wave is up to 30%of that in the non-magnetic medium.Also,comparing the variations of the power vs.wave-number in the fixed frequency for the two waves,we found that the wave-numbers,in the which the ridges of the mode in magnetic field are placed,have been shifted onto the direction of higher wave-number with respect to the fundamental and p -modes of n=1,2,3 and that the wave-number shifts are increased with the frquency.However,the power depression is modiifed by the frequency,i.e.the acoustic waves suffer some absorption at some limited zones of the frequency.These observations indicate that the mode coupling (or mixing) of p -mode with the corresponding magnetoacoustic-gravity (MAG) waves is generated in the magnetic feild.The generation of the mode mixing supports the explanation that the mode conversion is probably as the prime mechanism for the absorption of p -mode by the sunspot.In addition,the converted MAG waves are absorbed further when they propagate into the spot flux tube(in which the magnetic fields are basically the vertical).The power absorbed is up to 20% of the (residual)power of the waves.No further conversion inside the tube are observed.