H. "Naitou

H. Kitagawa

S." Tokuda

National Institute for Fusion Science (NIFS-Repository)

§4. Gyro-fluid Simulation of Kinetic Internal Kink Modes Naitou, H., Kitagawa, H. (Ya1naguchi Univ. Eng.) Tokuda, S. (.J.A.E.R.I.) The collisionless reconnection process of the rn = 1 (poloidal) and n = 1 (toroidal) ki-netic internal kink 1node is sin1ulated by the three di1nensional two field (the electrostatic potential, ¢, and the co1nponent of the vector potential in the direction of toroidal 1nagnetic field, Az) gyro-fluid code including the effects of the electron inertia and the perturbed electron pressure gradient. dd (vi¢)= -v~ b* · \7(\?iAz), (1) f, a * {2 d ( 2 ) 2 * ( 2 ) -a Az = -b ·\7¢+ae-d \7 ..LAz +psb ·v \7 ..L¢, t 1 (2) where VA = c wc·d wpi ( c is the speed of light in vacuu1n and wei and wpi are the ion cyclotron and plas1na. angular frequencies, respectively) is the Alfven velocity, de = c/wpe (wpe is the electron plasrna. angular frequency) is the colli-sionless electron skin depth, Ps = jTefm,jwc-i (m.i is the ion rnass, Te is the electron temper-ature) is the ion Larmor radius calculated by the electron te1nperature, b* is the unit vector of the 1nagnetic field, b* = b vAz X b + Eo ' (3) and d/ dt is the convective derivative defined by !!_ = _g_ + b x v¢. v. dt at Eo (4) The external rnagnetic field is assurned to be B = B0 b where b is the unit vector. The cornputational 1nodel is a rectangular syste1n (Lx x Ly x Lz) which represents a straight tokarnak with periodic boundary con-dition in the z (toroidal) direction. The plasma is surrounded by the perfectly conducting walls in the x and y (poloidal) directions. The rnea-sured linear growth rates agree with the theory 250 1 2 in which 1 ex de for de >> Ps and 1 ex dl p] for de<< Ps (see Fig.1 and Fig.2). Also, results of the gyro-fluid code agree quite well with those of the gyrokinetic particle code ( GYR3D) for linear and early nonlinear phase of the instabil-ity. The co1nparison of both codes in the deeply nonlinear phase of the instability is in progress. c( I LJ = 0.03125 Ps I L.r = 0.0 0 0 2 '----'-----'-_____L___l_---'--L-'1 0__,__ _ 2_L___-'----------'---"---L-'-L..J.1 0-'-_-1 -'-----' p, I L.r Fig.l. The Psi Lx dependence of the growth rate of the kinetic internal kink mode for de/ Lx = 0.03125. Ps I L 1: = 0.125 1.0 -r: 0.9 ;:::, 0.8 -----... 0.7 y -...._,_.. (--Fig.2. The de/ Lx dependence of the growth rate of the kinetic internal kink rnode for Ps/ Lx = 0.125. 

Gyro-fluid Simulation of Kinetic Internal Kink Modes

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