A Comparison of Solar Open Field Regions Found by Type III Radio Bursts and the Potential Field Source Surface Model

Abstract

For heliophysics research and applications, the potential field source surface (PFSS) model is often employed to extrapolate the photospheric magnetic field to the corona. In an attempt to evaluate the performance of the PFSS model, we compare the computed footpoints of the heliospheric magnetic field with the locations of flares associated with type III radio bursts, which are a good indicator of open field lines that extend to interplanetary space. Consistent with past experiences, the agreement is not satisfactory. We discuss possible reasons for the discrepancy, including the model's inadequacy to reproduce the coronal magnetic field above evolving active regions and the lack of a simultaneous full-surface magnetic map. It is argued that the performance of the PFSS model needs to be quantified further against solar observations, including type III bursts, before it is applied to heliospheric models.