Chaotic dynamics of nonthermal planetary radio emissions

A dynamical theory of nonlinear three-wave interactions involving Langmuir, whistler and Alfven waves in the planetary magnetospheres is developed. By assuming linear growth for the Langmuir wave and linear damping for both whistler and Alfven waves, the wave triplet is shown to evolve temporarily from order to chaos via either the period doubling route or the type-I Pomeau-Manneville intermittency route. Numerical solutions of this dynamical system are presented, showing the time series of the wave amplitude and the corresponding power spectra. The characterization of orderly and chaotic states is performed by plotting the Poincare maps and calculating the largest Lyapunov exponent. The relevance of this theory for observation of chaos in the time series of nonthermal planetary radio emissions is discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.