Resonant Absorption of Fast Magnetoacoustic Waves due to Coupling into the Slow and Alfvén Continua in the Solar Atmosphere
Resonant Absorption of Fast Magnetoacoustic Waves due to Coupling into the Slow and Alfvén Continua in the Solar Atmosphere
复制标题
由于耦合到太阳大气中的慢磁声波和阿尔文连续磁波而产生的快磁声波的共振吸收
DOI：
10.1007/s11207-010-9578-4
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发表时间：
2010
期刊：
影响因子：
2.8
通讯作者：
Clack C
中科院分区：
文献类型：
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作者：
Clack C
研究了快速磁声（FMA）波在非均匀、弱耗散、一维平面、强各向异性和色散等离子体中的共振吸收。磁结构由夹在两个半无限均匀磁等离子体区域之间的非均匀磁板组成。横向驱动的FMA波与存在于非均匀层中的局部慢波或alfvsamn波相互作用，穿透非均匀板，并被该区域部分反射、消散和传输。本研究旨在求出太阳色球和日冕条件下的波能吸收系数。对数值计算结果进行了分析，找出了慢速共振位置和阿尔夫萨芬共振位置的波能吸收系数。数学推导基于两个简化假设：1)非线性较弱；2)非均匀层的厚度相对于波的波长较小。我们采用所谓的长波长近似。发现慢共振可以用非线性理论来描述，而在alvsamn共振处的动力学可以用线性框架来描述。我们引入了耦合共振的新概念，耦合共振发生在两个不同的共振彼此非常接近时，导致入射波似乎同时受到两个共振的影响。结果表明，波能的吸收与入射波的角度以及平衡磁场的倾角密切相关。此外，还发现在冠状条件下，FMA波在alv<s:1>共振处被非常有效地吸收。在色球条件下，尽管由于耦合共振而提高了效率，但FMA波的吸收效率要低得多。
Resonant absorption of fast magnetoacoustic (FMA) waves in an inhomogeneous, weakly dissipative, one-dimensional planar, strongly anisotropic and dispersive plasma is investigated. The magnetic configuration consists of an inhomogeneous magnetic slab sandwiched between two regions of semi-infinite homogeneous magnetic plasmas. Laterally driven FMA waves penetrate the inhomogeneous slab interacting with the localised slow or Alfvén waves present in the inhomogeneous layer and are partly reflected, dissipated and transmitted by this region. The presented research aims to find the coefficient of wave energy absorption under solar chromospheric and coronal conditions. Numerical results are analysed to find the coefficient of wave energy absorption at both the slow and Alfvén resonance positions. The mathematical derivations are based on the two simplifying assumptions thati) nonlinearity is weak, andii) the thickness of the inhomogeneous layer is small in comparison to the wavelength of the wave,i.e.we employ the so-called long wavelength approximation. Slow resonance is found to be described by the nonlinear theory, while the dynamics at the Alvén resonance can be described within the linear framework. We introduce a new concept of coupled resonances, which occurs when two different resonances are in close proximity to each other, causing the incoming wave toact as thoughit has been influenced by the two resonances simultaneously. Our results show that the wave energy absorption is heavily dependent on the angle of the incident wave in combination with the inclination angle of the equilibrium magnetic field. In addition, it is found that FMA waves are very efficiently absorbed at the Alvén resonance under coronal conditions. Under chromospheric conditions the FMA waves are far less efficiently absorbed, despite an increase in efficiency due to the coupled resonances.