Vector Magnetograms - From Photosphere to the Base of the Solar Corona
Abstract
The magnetic field in solar active regions is currently a major topic of research in solar physics. While hard to measure directly, it is commonly modeled with the use of photospheric magnetograms. An assumption that is often made in such modeling is that the plasma beta is small in the rarefied corona and therefore an equilibrium configuration requires that the Lorentz force vanishes through the volume. While this assumption greatly simplifies the modeling, it also complicates the use of the photospheric magnetic field as a boundary condition, as the photosphere is not in general a low-beta environment. While vector magnetograms at the base of the low-beta corona are not routinely available, the photospheric magnetograms continue to be widely used for coronal modeling. Additional steps, such as pre-processing, can be taken during the modeling to make these data as consistent with the low-beta equilibria as possible. In this work, we attempt to analyze how much do magnetograms of the coronal base differ from those of the photosphere, analyze their morphology, magnitude and how they change with height. For this, we analyze some of the most realistic full-MHD simulations of active regions made with MURaM code. They simulation volume includes upper convection zone, photosphere, transition region, and the corona. While they are not simulations of a specific active region, they appear extremely realistic in wide range of diagnostics, from the magnetic field in the photosphere, to the coronal morphology, to evolution typically observed in active regions. We study these simulations and the synthetic data they produce, focusing on the applicability of vector magnetograms to low-beta coronal magnetic modeling. We also describe some alternative methods of gathering vector magnetograms of the chromosphere from the coronal morphology, and compare them to the actual structures of the simulations.
- Publication:
-
2018 Triennial Earth-Sun Summit (TESS)
- Pub Date:
- May 2018
- Bibcode:
- 2018tess.conf20234M