EGU General Assembly 2021
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Preprocessing of magnetograms for magnetohydrostatic extrapolations

Xiaoshuai Zhu1, Thomas Wiegelmann2, and Bernd Inhester2
Xiaoshuai Zhu et al.
  • 1National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China (
  • 2Max-Planck-Institut für Sonnensystemforschung

Magnetohydrostatic (MHS) extrapolations are developed to model 3D magnetic fields and plasma structures in the solar low atmosphere by using measured vector magnetic fields on the photosphere. However, the photospheric magnetogram may be inconsistent with the MHS assumption. By applying Gauss‘ theorem to an isolated active region, we obtain a set of surface integrals of the magnetogram as criteria for a MHS system. The integrals are a subset of Aly’s criteria for a force-free field (FFF). Based on the new criteria, we preprocess the magnetogram to make it more consistent with the MHS assumption and, at the same time, close to the original data. As a byproduct, we also find the boundary integral that is used to compute the energy of a FFF usually underestimates the magnetic energy of an active region.

How to cite: Zhu, X., Wiegelmann, T., and Inhester, B.: Preprocessing of magnetograms for magnetohydrostatic extrapolations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1973,, 2021.


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