An elliptic expansion of the potential field source surface model

¹ University of Kiel, Institute for Experimental and Applied Physics, Leibnizstr. 11, 24118 Kiel, Germany
e-mail: kruse@physik.uni-kiel.de
² University of Kiel, Department of Mathematics, Ludewig-Meyn-Str. 4, 24118 Kiel, Germany

Received: 14 February 2020
Accepted: 19 March 2020

Abstract

Context. The potential field source surface model is frequently used as a basis for further scientific investigations where a comprehensive coronal magnetic field is of importance. Its parameters, especially the position and shape of the source surface, are crucial for the interpretation of the state of the interplanetary medium. Improvements have been suggested that introduce one or more additional free parameters to the model, for example, the current sheet source surface model.

Aims. Relaxing the spherical constraint of the source surface and allowing it to be elliptical gives modelers the option of deforming it to more accurately match the physical environment of the specific period or location to be analyzed.

Methods. A numerical solver is presented that solves Laplace’s equation on a three-dimensional grid using finite differences. The solver is capable of working on structured spherical grids that can be deformed to create elliptical source surfaces.

Results. The configurations of the coronal magnetic field are presented using this new solver. Three-dimensional renderings are complemented by Carrington-like synoptic maps of the magnetic configuration at different heights in the solar corona. Differences in the magnetic configuration computed by the spherical and elliptical models are illustrated.