jeudi 17 septembre 2015, par Antonia Savcheva (Harvard-Smithsonian Center for Astrophysics, USA)
Lundi 21 septembre 2015 à 11h00 , Lieu : Salle de conférence du bâtiment 17
A long established goal of solar physics is to build physics-based flare and CME forecasting models. This study, building on the recent successes in non-linear forces free field (NLFFF) modeling and detailed numerical simulations, brings us closer to that goal. In the first part of the talk, I show that data-constrained NLFFF models built to reproduce the active region magnetic field in the pre-flare state can be rendered unstable and the sequence of unstable solutions produce quasi-separatrix layers (QSLs) that reproduce the observed flare ribbons. The results are fully consistant with the 3D extension of the standard flare/CME model. Three active regions are studied using SDO/AIA and HMI to constrain NLFFF models. Stable models that are well matched to pre-flare coronal loops are rendered unstable by the addition of axial magnetic flux. This results in a series of solutions in the magneto-frictional relaxation with the flux rope evolving to different heights. We present maps of the QSLs and current in cross sections through the flux ropes, which present the dynamical nature of the solutions. We compare the chromospheric maps of the squashing factor, Q, with flare ribbon positions at different times during the flare.
In the second part of the talk, we go beyond the initial moments of the eruption to explore the CME from one of the regions that we have performed the topology analysis. We perform the first global data-constrained MHD simulation of a CME with the Space Weather Modeling Framework (SWMF). The initial condition for the simulation is the unstable model obtained with the flux rope insertion method of the active region CME on April 08, 2010. The boundary condition is a synoptic magnetogram from SOLIS, with a high resolution HMI piece around the active region. We discuss the newly developed capabilities built-in into SWMF for producing fully data-constrained models of CMEs. We show the initiation and propagation of the CME within 10Rsun. We compare simulated LASCO white light and SDO/AIA EUV images with the observations and demonstrate the power of using data to constrain the initial and boundary conditions ion such a simulation.