Evaluating (and Improving) Estimates of the Solar Radial Magnetic Field Component from Line-of-Sight Magnetograms
Abstract
Although for many solar physics problems the desirable or meaningful boundary is the radial component of the magnetic field Br, the most readily available measurement is the component of the magnetic field along the line of sight to the observer, Blos. As this component is only equal to the radial component where the viewing angle is exactly zero, some approximation is required to estimate Br at all other observed locations. In this study, a common approximation known as the "μ -correction", which assumes all photospheric field to be radial, is compared to a method that invokes computing a potential field that matches the observed Blos, from which the potential field radial component, Brpot is recovered. We demonstrate that in regions that are truly dominated by a radially oriented field at the resolution of the data employed, the μ -correction performs acceptably if not better than the potential-field approach. However, it is also shown that for any solar structure that includes horizontal fields, i.e. active regions, the potential-field method better recovers both the strength of the radial field and the location of magnetic neutral line.
- Publication:
-
Solar Physics
- Pub Date:
- February 2017
- DOI:
- 10.1007/s11207-017-1057-8
- arXiv:
- arXiv:1701.04836
- Bibcode:
- 2017SoPh..292...36L
- Keywords:
-
- Magnetic fields;
- models;
- photosphere;
- Active regions;
- magnetic fields;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Instrumentation and Methods for Astrophysics
- E-Print:
- Accepted for publication in Solar Physics