2:45 PM - 3:00 PM
[PEM07-21] Propagation and reflection of nonlinear Alfven wave in the solar chromosphere
Keywords:chromospheric heating, Alfven wave, magnetic diffusion, nonlinear
In this study, we investigate the reflection of Alfvén waves propagating along a vertically open magnetic flux tube in the chromosphere at the transition region and photosphere. If we assume the atmospheric condition in the solar quiet region, the damping length of waves which have frequencies of 1--100 mHz by the magnetic diffusion is estimated to become much larger than the thickness of the chromosphere. For investigating the dissipation of Alfvén waves in the chromosphere, we should consider the condition where the reflection at the photosphere and transition region efficiently occurs and more Alfvén waves are trapped in the chromosphere. We investigate the propagations of the nonlinear Alfvén waves by performing one-dimensional numerical simulations. As a result, 60--70 % of the incident Alfvénic pulse waves with frequencies of 10--100 mHz are reflected at the transition region. Most of reflected waves from the transition region penetrate into the convection zone without being reflected at the bottom of the photosphere. We perform simulations in different magnetic field structures and confirm that the results are almost the same in any cases. It is considered to be important to take the energy flux going from the top and bottom boundaries of the chromosphere into account for the dissipation of Alfvén waves in the chromosphere. In the case where the initial velocity amplitude of Alfvén wave is set to be 1.0 km s-1, the compressible waves generated by the nonlinear effect may have enough energy to heat the chromosphere. If the initial velocity amplitude is set to be smaller, less compressible waves are generated and other dissipation mechanisms of the Alfvén waves may become effective.