Investigation of the turbulent equipartition establishment in tokamaks

For a moderate level of turbulence, the self-consistent nonuniform profiles of the turbulent equipartition (TEP) of the density and temperature distri bution of magnetized electrons in a tokamak were found analytically and num erically. Only conservation of the adiabatic invariants of the electrons is needed for the solution of this problem. For passing electrons, the profil e of the density is determined mainly by the flat radial dependence of the helicity (AB)(r), in contrast to the pinched profile similar to 1/q of the trapped electrons determined by the safety factor q(r). The numerically obt ained, combined profile of the electron density n similar to 1/q(0.58) was found to be similar to a particular experimental scaling. Also, it was asce rtained that the high pinching of the temperature profile is mainly determi ned by the heating of passing electrons in the potential energy well of the poloidal magnetic field, and depends on the beta(phi) (ratio of the therma l energy to the magnetic one) value. Large values of beta(phi) give small t emperature pinching. The TEP distribution also gives one the possibility to obtain self-consistently the profile and the level of the turbulent fluctu ations due to the development of quick kinetic instabilities associated wit h the TEP distribution. The estimation of the time of turbulent mixing of t he electrons in the tokamak volume gives a realistic value of the order of 10 ms in the central part of tokamak and 0.1 s in the region near the separ atrix. (C) 1999 American Institute of Physics. [S1070-664X(99)00708-9].