LYAPUNOV EXPONENTS AND PARTICLE DISPERSION IN DRIFT-WAVE TURBULENCE

The Hasegawa-Wakatani model equations for resistive drift waves are so lved numerically for a range of values of the coupling due to the para llel electron motion. The largest Lyapunov exponent, lambda(1), is cal culated to quantify the unpredictability of the turbulent flow and com pared to other characteristic inverse time scales of the turbulence su ch as the linear growth rate and Lagrangian inverse time scales obtain ed by tracking virtual fluid particles. The results show a correlation between lambda(1) and the relative dispersion exponent, lambda(p), as well as to the inverse Lagrangian integral time scale tau(i)(-1). A d ecomposition of the flow into two distinct regions with different rela tive dispersion is recognized as the Weiss decomposition [J. Weiss, Ph ysica D 48, 273 (1991)]. The regions in the turbulent flow which contr ibute to lambda(1) are found not to coincide with the regions which co ntribute most to the relative dispersion of particles. (C) 1996 Americ an Institute of Physics.