Astropause boundary layer structures

The project is dedicated to the investigation of interaction regions between the flow of the interstellar medium with respect to a stellar wind. The interaction leads to instabilities, which might relax into (quasi-)equilibria in the frame of fluid theory forming a separatrix surface called the astropause. The astropause can show a porous structure on the inner stellar wind side.

The student will have to analyze flux functions and stream functions with suitable representations such as either higher order polynomials or non-linear solutions of the Grad-Shafranov equation in 2D or 2.5D. These representations lead to configurations with multiple magnetic nullpoints. The chosen flux functions should be used to solve the ideal or slightly non-ideal Ohm's law or the ideal or slightly non-ideal momentum equation with analytical or semi-analytical methods, to find corresponding velocity fields and probably reconnective structures with so-called X-points and O-points. The occurrence of these multiple magnetic null points (or in hydrodynamics stagnation points) corresponds to magnetic foam structures suggested to exist in the outer parts of the heliosphere or other astrospheres. This foam likely consists of magnetic bubbles formed e.g. by MHD instabilities or magnetic reconnection and could represent an analogy to vortex chains (or clusters) in different, non-magnetized stellar wind-interstellar medium interaction regions. The found solutions should be investigated as puzzle pieces of the nature of the larger stellar wind-interstellar medium interaction region. The derived fluid values, plasma flow velocity, magnetic field, density, pressure, temperature etc. can be used to create synthetic emission maps, which can be compared with observations.

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