Dynamics of Vortices on the Solar Photosphere

Abstract

The majority of studies on multi-scale vortex motions employ a two-dimensional geometry by using a variety of observational and numerical data. This approach limits the understanding of the na- ture of physical processes responsible for vortex dynamics. Here we develop a new methodology to extract essential information from the boundary surface of vortex tubes. 3D high-resolution mag- netoconvection MURaM numerical data has been used to analyse photospheric intergranular velocity vortices. The Lagrangian Aver- aged Vorticity Deviation (LAVD) technique was applied to define the centers of vortex structures and their boundary surfaces based on the advection of fluid elements. These surfaces were mapped onto a constructed envelope grid that allows the study of the key plasma parameters as functions of space and time. Physical quan- tities that help in the understanding of plasma dynamics were also identified. Our results suggest that, while density and pressure have a rather global behaviour, the other physical quantities un- dergo local changes, with their magnitude and orientation changing in space and time. At the surface, the mixing in the horizontal di- rection is not efficient, leading to appearance of localized regions with higher/lower temperatures. In addition, the analysis of the MHD Poynting flux confirms that the majority of the energy is di- rected in the horizontal direction. Our findings also indicate that the pressure and magnetic forces that drive the dynamics of the plasma on vortex surfaces are unbalanced and therefore the vor- tices do not rotate as a rigid body. Next, we investigate the signatures of waves that might propagate via vortices. The objective of this study is to construct basic ro- tating magnetic flux tubes and then to analyse the existence and signature of local and global waves travelling through solar vortex tubes. The Proper Orthogonal Decomposition (POD) technique was used to analyse the wave morphology.