Stability of diocotron modes
In the cold plasma limit, 2-D perturbations in electrostatic potential are forbidden, not by symmetry and lack of a dissipation mechanism, but by the topology of the magnetic field
Therefore, “regular” diocotron modes are stable even in the presence of dissipation or asymmetries in the trap
The trap may be stable even in the presence of a finite ion density
- Proven to work for quasi-neutral plasmas
Even in warm plasmas, the fluid flow does not cross magnetic surfaces
Fluid instabilities will have to violate one of the assumptions of the derivation shown. E.g., perpendicular diocotron oscillations could couple to parallel electron plasma oscillations (O’Neil, 2001)
- Breaks force balance along field lines
- Would be damped either by Landau damping (for sufficiently high temperature) or magnetic shear (Yoshida et al., 2001)