Negative-energy perturbations in circularly cylindrical equilibria within the framework of Maxwell-drift kinetic theory
The conditions for the existence of negative energy perturbations (which could be nonlinearly unstable and cause anomalous transport) are investigated in the framework of linearized collisionless Maxwell-drift kinetic theory for the case of equilibria of magnetically confined, circularly cylindrical plasmas and vanishing initial field perturbations. For wave vectors with a nonvanishing component parallel to the magnetic field, the plane equilibrium conditions are shown to remain valid, while the condition for perpendicular perturbations (which are found to be the most important modes) is modified. Consequently, besides the tokamak equilibrium regime in which the existence of negative energy perturbations is related to the threshold value of two-thirds of the quantity eta (nu), a new regime appears, not present in plane equilibria, in which negative energy perturbations (active particles). In particular, for linearly stable equilibria of a paramagnetic plasma with flat electron temperature profile, the entire velocity space is occupied by active electrons. The part of the velocity space occupied by active particles increases from the centre to the plasma edge and is larger in a paramagnetic plasma than in a diamagnetic plasma with the same pressure profile. It is also shown that, unlike in plane equilibria, negative energy perturbations exist in force free reversed field pinch equilibria with a substantial fraction of active particles.
Bibliographic Reference: Article: Physical Review E, Vol. 53 (1996) No.3, pp. 2767-2777
Record Number: 199610697 / Last updated on: 1996-06-21
Original language: en
Available languages: en