" Using Photospheric Data to Drive Coronal Field Models"

Abstract:  IFlares and coronal mass ejections (CMEs) are driven by the release of free magnetic energy stored in the coronal magnetic field. While this energy is stored in the corona, photospheric driving must play a central role in its injection, storage, and release, since magnetic fields present in the corona originated within the solar interior, and are anchored at the photosphere. Also, the corona's low diffusivity and high Alfven speed (compared to that at the photosphere) imply that the large-scale coronal field essentially maintains equilibrium (outside of episodic flares and CMEs!), and therefore only evolves due to forcing from photospheric evolution. But fundamental questions about each stage of this "storage and release" paradigm remain: How is free magnetic energy introduced into the corona? How is this energy stored? And what triggers its release? The unprecedented combination of high cadence, resolution, and duty cycle of the HMI vector magnetograph enables modeling coronal magnetic evolution in response to photospheric driving, a powerful approach to addressing these questions. I will discuss our efforts to use HMI vector magneotgrams of AR 11158 to derive time-dependent boundary conditions for a data-driven coronal magnetic field model. These efforts will play a key role in the development of the Coronal Global Evolutionary Model (CGEM), a data-driven, time-dependent model of the global coronal field, recently funded by NASA and NSF through the LWS-Strategic Capability program.