Wiegelmann, Thomas
Thomas Wiegelmann
Phone: +49 551 384 979-155
Inhester, Bernd
Bernd Inhester
Phone: +49 551 384 979-477


Thomas Wiegelmann and Takashi Sakurai, "Solar Force-free Magnetic Fields," Living Rev. Sol. Phys. 9, 5 (2012).

How to apply

Open PhD Project

Code development to further improve coronal field extrapolations

The 3d magnetic corona   The solar magnetic field couples the solar interior with the photosphere and corona where it drives heating processes and eruptive phenomena. In the corona the magnetic energy is quasi-statically built up until it exceeds by far the energy stored in a potential magnetic configuration. This excess energy is intermittently released in parts by large eruptive phenomena, e.g. coronal mass ejections, flares and eruptive prominences, but also through small ones, such as explosive events and nano- and micro flares which are probably central for heating the solar corona. Knowledge regarding the coronal magnetic field therefore plays a key role for obtaining a better understanding of these phenomena. Most measurements of the magnetic field vector are restricted to the photosphere, so that the magnetic field needs to be extrapolated from there into the corona. High resolution vector magnetograms are available from ground based (SOLIS), balloon-born (Sunrise) and space born instruments (Hinode, SDO, in future Solar Orbiter). Codes for modelling the coronal magnetic field have been developed at the MPS and are continuously improved.

Animation of solar magnetic field simulation. Zoom Image
Animation of solar magnetic field simulation.
The solar magnetic field in a simulation. Zoom Image
The solar magnetic field in a simulation.

A PhD project in modelling   We have developed in the past a robust and award-winning force-free extrapolation code. We continuously seek to improve the stability and performance ofthe code, and add new features to it. The list of these improvements and extensions comprises

  • Extension of the computational domain to the entire corona (including polar regions for which accurate measurements become available from Solar Orbiter). To avoid numerical convergence problems around the poles the code should be implemented on a so called Ying-Yang grid (see image) or an unstructured grid.
  • Extension of the force-free constraint to take into account of a stationary solar wind dynamic pressure.
  • Improvement of the input boundary data for the extrapolation code.

The project would concentrate on one or two of these topics and requires some knowledge in applied mathematics.

Image of the Yin-Yang Grid courtesy of Akira Kageyama. Zoom Image
Image of the Yin-Yang Grid courtesy of Akira Kageyama.
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