Seminar

Astrophysical plasmas exist in a large

range of length-scales throughout the universe. At sufficiently small scales, one must

account for many two-fluid effects, such as the ion or electron skin-depths, as well as

Larmor radii. These effects occur when ignoring electron mass, for example, is no longer

possible. We are interested in studying idealized turbulence in the context of such Hamil-

tonian plasma models which include two-fluid effects. In particular, we look at a extended

2D MHD model which includes the electron skin-depth.This model has been applied to

understanding collisionless reconnection in past. Two-dimensional simulations are less

computationally intensive and thus allow us to perform a parameter study of many runs,

in which we look at the cascade of conserved quadratic quantities (that happen to be

Casimir invariants of the Poisson bracket) as we vary the effective electron skin-depth.

We find that the cascade directions depend strongly on whether these length scales are

relevant in the system, and, furthermore, that these transitions in cascade directions

happen in a critical way, as was previously observed in other studies of the kind but in

different systems. Finally, we compare these results to predictions made by the authors

in a previous theoretical study using Absolute Equilibrium States.