Direction of cascades in a magnetofluid model with electron skin depth and ion sound Larmor radius scales

George Miloshevich (1) , Philip Morrison (1) , Emanuele Tassi (2, 3, 4)

1 IFS - Institute for Fusion Studies
2 CPT - Centre de Physique Théorique - UMR 7332
3 CPT - E7 Systèmes dynamiques : théories et applications
4 LAGRANGE - Joseph Louis LAGRANGE

The direction of cascades in a two-dimensional model that takes electron inertia and ion sound Larmor radius into account is studied, resulting in analytical expressions for the absolute equilibrium states of the energy and helicities. These states suggest that typically both the energy and magnetic helicity at scales shorter than the electron skin depth have a direct cascade, while at large scales the helicity has an inverse cascade as established earlier for reduced magnetohydrodynamics (MHD). The calculations imply that the introduction of gyro-effects allows for the existence of negative temperature (conjugate to energy) states and the condensation of energy to the large scales. Comparisons between two- and three-dimensional extended MHD models (MHD with two-fluid effects) show qualitative agreement between the two

Domaines: Physique des plasmas [physics.plasm-ph]; Astrophysique stellaire et solaire [astro-ph.SR]; Dynamique des Fluides [physics.flu-dyn]

George Miloshevich, Philip Morrison, Emanuele Tassi. Direction of cascades in a magnetofluid model with electron skin depth and ion sound Larmor radius scales. Physics of Plasmas, 2018, 25 (7), pp.072303. ⟨10.1063/1.5023089⟩. ⟨hal-02069006⟩