Local topology, multi-scale interactions and stochasticity in space plasma physics

Abstract:

In space physics very important phenomena, as reconnection, are determined by the local topology of the streamlines and magnetic lines of plasma, and by multi-scale interactions. In this work, an attempt is presented to deal with dynamical variables highlighting both the local topology and the role of space scale.

In order to promote local topology to the role of a dynamical variable, use is made of the gradients of the velocity and of the magnetic field, through which the description of the local topology becomes very transparent. Such a formulation, well explored in Hydrodynamics, is extended here to the MHD.

The new dynamical variables evolve in a finite scale stochastic dynamics: letting the scale appear explicitly as a variable of the problem helps studying inter-scale processes, while statistical aspects of topological variable dynamics are expected to be extremely relevant in the turbulent regime, where a stochastic field scenario is, in practice, taking place.