  A standard model for eruptive flares aims at describing observational 3D
features of the reconnecting coronal magnetic field. Extensions to the 2D model
require the physical understanding of 3D reconnection processes at the origin
of the magnetic configuration evolution. However, the properties of 3D
reconnection without null point and separatrices still need to be analyzed. We
focus on magnetic reconnection associated with the growth and evolution of a
flux rope and associated flare loops during an eruptive flare. We aim at
understanding the intrinsic characteristics of 3D reconnection in the presence
of quasi-separatrix layers (QSLs), how QSL properties are related to the
slip-running reconnection mode in general, and how this applies to eruptive
flares in particular. We studied the slip-running reconnection of field lines
in a magnetohydrodynamic simulation of an eruptive flare associated with a
torus-unstable flux rope. Field lines associated with the flux rope and the
flare loops undergo a continuous series of magnetic reconnection, which results
in their super-Alfvenic slipping motion. The time profile of their slippage
speed and the space distribution of the mapping norm are shown to be strongly
correlated. We find that the motion speed is proportional to the mapping norm.
Moreover, this slip-running motion becomes faster as the flux rope expands,
since the 3D current layer evolves toward a current sheet, and QSLs to
separatrices. The present analysis extends our understanding of the 3D
slip-running reconnection regime. We identified a controlling parameter of the
apparent velocity of field lines while they slip-reconnect, enabling the
interpretation of the evolution of post flare loops. This work completes the
standard model for flares and eruptions by giving its 3D properties.
