Exploring The Time-Evolving Corona

MHD simulations of the solar corona based on maps of the solar magnetic field have been demonstrated to describe many aspects of coronal structure. These models have increased in sophistication over the years, and their output can be used to simulate many observables, including EUV and X-ray emission, scattering of white-light, and ion charge-state abundances. However, these models are typically integrated to steady state, using synoptic or daily updated magnetic maps to derive the boundary conditions. The Sun’s magnetic flux is constantly evolving, and these changes in the flux affect the structure and dynamics of the corona and heliosphere. The dynamics may be crucial to understanding solar wind properties, such as the formation of the slow solar wind. In this presentation, we describe an approach to evolutionary models of the corona and solar wind, using time-dependent boundary conditions. We use the Lockheed Surface Flux Transport (SFT) model to evolve the surface magnetic fields, which in turn drive the coronal evolution. To mitigate issues with the limited Sun-Earth viewpoint of presently available magnetographs that can cloud the interpretation of time-dependent evolution, we employ a “simulated Sun” version of the Lockheed SFT that emerges new flux over the entire Sun with solar-like properties. The simulations are performed with the MAS thermodynamic Wave-Turbulence Driven (WTD) model for a month of simulated time. We use the simulated observables derived from the simulation to explore the evolution of coronal structure (e.g., coronal hole boundaries) and compare and contrast the results with MHD solutions using static magnetic flux boundaries at selected times.

Research supported by NASA and NSF.