Abstract
For many decades, Alfvén waves have been considered to be a source of energy in the solar coronal plasma and supersonic wind. It’s important to understand the possible dissipation mechanism of the Alfvén waves in the heterogeneously structured corona. Magnetic singularities allow mode conversion of the MHD waves from the vicinity of the equipartition layer (Cs≈CA). In our study, we have performed a 2.5D MHD numerical simulation of the Alfvén wave packet generation through the mode conversion when a fast wave interacts with the localized magnetic null in the corona. Subsequently, the out of the plane velocity (i.e., Vz) and magnetic field fluctuations (i.e., bz) are generated from the equi-partition layer (Cs≈CA) and seen to propagate towards the large scale heterogeneous corona. Also, the Alfvén wave packet shows decay in amplitude on the curved magnetic field, owing to the phase mixing due to the gradient of local Alfvén speed across the magnetic field. Moreover, the strength of the phase mixing depends on the amplitude of the local transverse gradient of bz, which then helps to form localized current layers. So, our results demonstrate that Alfvén waves can be generated from the magnetic null through MHD mode conversion, which undergoes damping due to phase mixing and propagates towards another null in the vicinity. We finally infer that realistic physical conditions are required to establish the extent of phase mixing and dissipation in the structured solar corona.
Co-authors
Abhishekh K. Srivastava (IIT BHU, Varanasi, India); T.V. Zaqarashvili (University of Graz, Graz, Austria); Juan Martinez-Sykora (SETI Institute, Mountain View, CA, USA); Bart D. Pontieu (LMSAL, Palo Alto, USA), Ding Yuan (HIT Shenzhen, China); Sripan Mondal (IIT BHU, Varanasi, India); P. Bourdi (University of Graz, Graz, Austria); Ryun-Young Kwon (KASI, Republic of Korea); Astrid Veronig (University of Graz, Graz, Austria)