Modeling the 1994 April 14 Polar Crown SXR Arcade Using Three-Dimensional Magnetohydrostatic Equilibrium Solutions

Abstract

The coronal magnetic field in the polar crown soft X-ray (SXR) arcade of 1994 April 14 has been computed using the global photospheric magnetic field distribution constructed for the time of interest and the three-dimensional magnetohydrostatic equilibrium solutions. In the solutions there are two free parameters, α and a, respectively, characterizing the effect of the field-aligned and horizontal electric currents. Magnetic field configurations have been determined for various combinations of α and a. The magnetic arcade computed with α-->0 and a=0.9 agrees best in shape and size with the well-developed polar crown SXR arcade. This suggests that the well-developed SXR arcade has a potential-like magnetic configuration with non-field-aligned currents. The computed loci of the apexes of lines of force that close above 1.3 R_solar match the shape of the bright axial features superposed on the well-developed SXR arcade. This suggests that newly opened lines of force may have reconnected only above 1.3 R_solar, and consequently the pre-eruption closed lines of force may not be completely opened up during the eruption phase. The SXT images before the formation of the SXR loop show the occurrence of dimmings, supporting the inference of partially ``transient'' coronal opening.