Slideaway distributions and relevant collective modes in hightemperature plasmas
Abstract
The evolution of the electron distribution function is analyzed in the case where an electric field that is not too small in comparison with the critical electron runaway field is applied along the confining magnetic field of a hightemperature plasma. In the regimes considered, a finite fraction of the electron population has magnetically trapped orbits and is not appreciably affected by the applied electric field, while the distribution of circulating electrons tends to 'slide away' as a whole. The role that collective modes and collisions can play in producing a stationary electron distribution is analyzed. Modes at the ion plasma frequency, which are driven by the positive slope of the currentcarrying electron distribution, can be excited when the average electron drift velocity is a finite fraction of the electron thermal velocity, and will transfer transverse energy to the main body of the electron distribution. These features are consistent with experimental observations performed on the Alcator device. Modes at the 'reduced' electron plasma frequency can also be excited both in connection with the modes at the ion plasma frequency and independently. Modes at the electron gyrofrequency associated with the losscone feature that the electron distribution tends to develop are considered, among others, as a factor for the strongly enhanced electron cyclotron emission experimentally observed in regimes where nonthermal electron distributions have been realized.
 Publication:

Nuclear Fusion
 Pub Date:
 April 1976
 Bibcode:
 1976NucFu..16..309C
 Keywords:

 Distribution Functions;
 Electron Distribution;
 High Temperature Plasmas;
 Magnetically Trapped Particles;
 Plasma Frequencies;
 Toroidal Plasmas;
 Collisionless Plasmas;
 Electric Fields;
 Electron Energy;
 Electron Plasma;
 Ion Cyclotron Radiation;
 Magnetic Fields;
 Plasma Control;
 Vlasov Equations;
 Plasma Physics