Development of steady-state solar polar plume models in one and two dimensions to investigate solar wind sources

Solar plumes are bright radial rays with higher density and lower temperature than the surrounding interplume medium, which occur on the polar areas of the Sun where the high-speed solar wind is known to originate. Polar plumes provide a unique opportunity for understanding solar wind sources and the heating of open-field regions in the corona. We have used the equations of magnetohydrodynamics (MHD) and simultaneous observations of polar plumes in the emission of Fe XII (Te ∼ 1.5 MK) and H Lyman alpha (20,000 K ≤ Te ≤ 70,000 K) to study the heating and dynamics of polar plumes. One-dimensional (1D) and two-dimensional (2D) steady-state polar plume models have been developed. To investigate the impact of the location of heating input, a parameter study has been performed with the 1D plume model where the dissipation length of the heating has been varied. The 2D model we construct is the first solar wind model that takes into account transverse mass loss from coronal structures to investigate the effect of this new physics. The result of our dissipation length study was that the 1D model we have constructed are insensitive to the scale-height of the basal heating input. For our 2D model we found that these models, consistent with observations, have lower velocities than models that do not take transverse mass loss into account. It was additionally determined that the 2D mass loss models resulted in greater thermal conductive flux. This may explain the high luminosities of the plumes' footprints as observed in lower transition region and chromospheric emission lines. We conclude that basal heating models with variable heating are insufficient for evaluating the impact of the location of energy input. We also find that the new physics of transverse mass loss may be important for accounting fully for plume dynamics. Future work may include fully modeling the impact of the magnetic fields on plume dynamics. In particular, recent observations from the Hinode satellite's X-Ray Telescope suggest that polar plumes are basally heated via magnetic reconnection (as assumed in our models) but may also be subjected to further plasma accelerations at higher altitudes due to Alfven waves on the magnetic field. Once such models are constructed, it may be worthwhile to expand them to two-fluid models that consider protons and electrons separately. Further improvement may also be made in the computational approach. Advanced methods for matching the critical point conditions and more stable methods for integrating beyond the critical point will be explored.