| 介紹 | In order to obtain a fast magnetic reconnection
we need some mechanisms that enhance the
effective magnetic diffusivity. Turbulence is
considered to be one of such candidates.
Focusing on the turbulence effects in the mean
magnetic
-
field evolution, we construct a
system of turbulence model, where the tu
rbulent evolution is solved through the transport equations of
several turbulent statistical quantities, in addition to the mean
-
field equations for the density,
momentum, and energy. Numerical results showed that a slow laminar
-
like reconnection for very
weak
turbulence, and just a turbulent diffusion of the mean magnetic field (no fast reconnection) for too
much turbulence. Another interesting point is the role of the cross helicity (velocity
--
magnetic
-
field
correlation). The dynamic balance between the t
ransport enhancement and suppression due to
turbulence, the turbulent cross helicity contributes to localization of the effective magnetic diffusivity,
leading to a fast reconnection. |