随机磁场中的双极电场与双极扩散

等离子体中存在随机场输运时,必然会导致双极电场。本文给出了存在电场时,粒子在随机场中的转移几率,由此可计算输运流、双极电场等。算出的双极电场与碰撞的关系是不灵敏的((|e|E)/T_e=-A1/n_e(dn_e)/(dx),A与碰撞有关,但A～1)。并指出,此双极电场可作为判断随机场是否重要的必要条件(但非充分条件)。在随机场双极扩散中,杂质流速大于氢离子流速(V_I/V_i≈(m_i/

THE AMBIPOLAR ELECTRIC FIELD AND THE AMBIPOLAR DIFFUSION IN A STOCHASTIC MAGNETIC FIELD

It is shown that the transport of the plasma immersed in a stochastic magnetic field (s.m.f.) must lead to the producing of an ambipolar electric field. In this paper, the transition probability of charged particels in the s.m.f. was derived in the case of existing a transverse electric field. The transport fluxes and the ambipolar electric field were then calculated. The result shows that the ambipolar electric field is insensitive to the collision between particles. ((|e|E)/T_e=-A1/n_e(dn_e)/(dx), A is a coefficient ofabout 1, which depends on collision insensitively.) This ambipolar electric field may be used as a necessary (but not sufficient) criterion of ascertaining whether the effect of s.m.f. on the plasma transport is important. In the transport process induced by s.m.f. the impure ions transport more rapidly than hydrogen ions (V_I/V_i≈m_i/m_I]^1/2Z_I>1), this result can be used to explain the phenomenon in Tokamak experiment, i.e., when there appears interior disruption, the impurities will be extracted from centre region instead of being cumulated. We discussed also the effect of collision and the condition under which the above treat-ment is applicable. In the case of high collision, the diffusion flux is a much smaller quantity. The corresponding dynamic equation of plasma in a s.m.f. has been derived, it is somewhat different from that obtained by K. Molvig et al. in 3].