3D tracking of small-scale solar flux tubes

The Sun is the basis for all life on Earth but on the other side, its large energy outbursts on towards the Earth can damage satellites, endanger astronauts or even cause electrical power outages. The forecast of space weather related hazardous phenomena is essential to minimize the far reaching consequences. Hence, a better understanding of internal solar processes and the heating of the outer atmospheric layers is required. The dynamic of the solar atmosphere is governed by the magnetic field which is generated partly by convective motions of plasma and the global dynamo. New high resolution telescopes expose the magnetic and convective phenomena down to extremely small scales. Because of the high opacity of the solar photosphere observations of the underlying layer are not possible. The evolution of magnetic field lines and convective motions can only be simulated via 3D models models based on magnetohydrodynamics (MHD) equations. Solar telescopes as well as 3D models produce huge amounts of data. The fast progress in hardware technologies and the increasing resolution of telescopes lead to an inevitable application of automated algorithms facilitating analysis and evaluations. This proposal presents an entirely new approach never employed before in the field of solar physics, namely the development of 2D and 3D segmentation algorithms applied to high resolution observational data and MHD simulations of the solar atmosphere and convection zone. The segmentation of magnetic flux tubes and convective up- and downflows in 3D enables an extracted representation to trace their evolution from the point of formation to their dissipation. The analysis of the convective cells and magnetic flux tubes in 2D and in 3D will help to understand the mechanism of the solar dynamo and the heating processes of the upper solar atmosphere.

The heating problem of the solar atmosphere is a topic that has been puzzling scientist for decades. In detail this means, that we still do not fully understand which processes lead to the fact that the corona, which is the outermost layer of the Sun, is so hot. Originating from the convection zone and the photosphere, many processes and mechanisms can be observed, such as magnetic reconnection or magnetohydrodynamic waves, which are able to explain the increasing temperatures in the direction towards the high layers of the solar atmosphere. Magnetohydrodynamic simulations allow us to model and interpret the underlying physical processes. Several publications have showed, that the heating processes in the corona and the chromosphere result from dynamical processes originating in the convection zone, such as the granules in the photosphere. For that reason, we developed a segmentation algorithm in the course of this project in order to analyze and detect small convective cells. This algorithm is based on image processing techniques, which can be applied to several parameters in the convection zone. Furthermore, we developed a tracking algorithm to analyze the dynamics of small scale structures in the photosphere as well as to track the temporal evolution of the granules and therefore to find information about their origin. Moreover, the structure and the dynamics of the photosphere were analyzed by using high-resolution data of the convection zone which was taken from well-known radiative hydrodynamic simulation codes. These data supplement the results of our newly developed segmentation algorithm and help us therefore to understand the processes in the convection zone more comprehensively. In order to connect the processes of the inner and the outer layers of the solar atmosphere, we additionally developed a new magnetohydrodynamic code. This code allowed us to simulate and study the propagation of coronal waves and its interaction with coronal holes. By performing these simulations we were able to observe different effects inside coronal holes and at their boundaries. Coronal holes are the darkest regions in the corona and they are of great interest for several reasons. One of those reasons is the fact that they are the source of so-called high-speed streams which influence the structure of the interplanetary space and therefore determine Space Weather. In the course of this project we were able to perform a comprehensive analysis of the different layers of the solar atmosphere and their underlying physical processes. Moreover, by analyzing the magnetic flux tubes and the convective cells we were able to create a link between observations and simulations and therefore to provide new results that help to understand the heating mechanism of the solar atmosphere better.