Azimuthal structures and turbulent transport in Penning discharge*

Azimuthal structures in Penning discharge are investigated in the 2D3V model of Penning discharge with the axial magnetic field. The discharge is supported by ionization from the axial electron beam. We show that the large (m=1) spoke and small scale structures occur due to Simon-Hoh and lower hybrid instabilities driven by the electric field, density gradient, and collisions. It is shown that the steady-state discharge can be supported in two different regimes with different types of observed azimuthal structures. The transition between the regimes is controlled by the total energy input to the discharge. In the first regime, with the pronounced m=1 spoke activity, energy absorption dominates the power input due to the radial current and self-consistent electric field. In another regime, with prevalent small-scale m>1 spiral structures, the total energy input is dominated by the direct input of the kinetic energy from the axial electron beam. The latter regime with the lower values of the anomalous transport occurs when the injected axial current and total energy input are reduced.