Nonlinear dynamics of Alfven waves in the solar atmosphere

The nonlinear evolution of a large-amplitude lefthand circularly polarized Alfven wave propagating along an ambient magnetic field in the solar atmosphere is investigated by studying numerically the stationary solutions of the derivative nonlinear Schrodinger equation, in the presence of dissipation and external forcing. The onset of Alfven turbulence due to a transition from order to chaos is discussed. We show that Alfven chaos can arise either from a saddle-node bifurcation or a global bifurcation. The former leads to the type-I Porneau-Manneville intermittency whereby the time series of the magnetic field fluctuations switches intermittently between periodic and turbulent states; the latter leads to the birth/destruction of a chaotic attractor via a boundary crisis. In addition, we show that Alfven intermittency can appear from a global bifurcation associated with an interior crisis whereby the time series of the magnetic field fluctuations switches intermittently between weakly and strongly turbulent states. The significance of this chaos theory of Alfven turbulence for solar atmosphere is considered.