Slip-running reconnection: a 3D extension to the standard model for eruptive flares

Miho Janvier, Observatoire de Paris

The two-dimensional standard (CSHKP) model is a clue in understanding the formation of post-flare loops and related CME during an eruptive flare. However, as observed in dedicated solar missions, the shapes and positions of flare ribbons along with the existence of shear in post-flare loops have revealed the necessity for three-dimensional models to be developed. The present work looks at the relaxation process of a freely expanding magnetic field modeled via a 3D magnetohydrodynamic simulation of an eruptive flare. I will introduce different proxies quantifying the shear and the expansion of the magnetic field and I will show that the reconnection-driven transfer of the differential magnetic shear along with the vertical straightening of the inner legs of the CME are the keys to the strong-to-weak shear transition often observed in SXR and EUV.

I will then concentrate on the mechanism of post-flare loop formation that is deeply related with slip-running reconnection. This regime corresponds to a continuous change of field-line connectivity in Quasi-Separatrix Layers (QSLs) that exist in narrow electric currents inside the ribbons predicted in my model. This 3D reconnection leads to the apparent slippage of field lines at super-Alfvnic velocities. In particular, I will show that slipping speeds are directly related to the geometry of QSLs and I will especially focus on the correlation between the slip-running speed motion and the field line mapping parameter that is used to defined QSLs. Finally, I will show that the temporal evolution of the QSLs can explain the magnetic field shear evolution from a topological point of view.