Lorenz Stenflo Research Articles

Chaotic behavior of ion-temperature-gradient driven drift-dissipative modes

A new set of nonlinear mode coupling equations for finite amplitude low-frequency electromagnetic waves has been derived for nonuniform, resistive, magnetized electron-ion plasma with sheared flows. At equilibrium, the plasma is assumed to have density, ion-temperature, magnetic field, and velocity gradients. The temporal behavior of the nonlinear mode coupling equations is found to be governed by eight coupled equations, which are the generalization of the Lorenz and Stenflo equations, admitting chaotic trajectories. The linear stability of the generalized Lorenz–Stenflo system of equations is also presented under different approximations. The results of the present investigation should be helpful in understanding the wave phenomena in space and tokamak plasmas.

Nonlinear dynamics and anomalous energy transport in an electrostatic ion-temperature-gradient driven drift-dissipative mode

By using Braginskii transport equations for ions and Boltzmann distribution for electrons, a new system of nonlinear equations governing the dynamics of low-frequency, short-wavelength electrostatic waves in the presence of equilibrium density, temperature, magnetic field, and electrostatic potential gradients has been derived. New ion-temperature-gradient (ITG) driven drift-dissipative modes are shown to exist. An expression for anomalous ion energy transport caused by nonthermal electrostatic fluctuations is also derived. Furthermore, possible stationary solutions of the nonlinear system are obtained in the form of double vortex. On the other hand, the temporal behavior of newly derived nonlinear dissipative systems can be described by the generalized Lorenz–Stenflo equations which admit chaotic solutions. The results of the present investigation should be helpful for understanding the wave phenomena in space and tokamak plasmas.

Chaos in the parallel sheared plasma flow driven electromagnetic turbulence in nonuniform magnetoplasmas

By employing the two-fluid model, a system of nonlinear equations for low-frequency electromagnetic waves in nonuniform collisional magnetoplasmas has been derived. The plasma contains both the equilibrium density gradient and sheared flows. In the linear limit, a local dispersion relation has been obtained and analyzed in several interesting limiting cases. It is found that equilibrium sheared plasma flows cause instabilities of Alfvén-type waves even in the absence of the density gradient. The numerical results also show a large growth rate of electromagnetic parallel velocity shear (PVS) mode compared to the electrostatic mode for some ionospheric parameters. For this case, the temporal nonlinear behavior of the relevant governing mode coupling equations is governed by six coupled equations, which are a generalization of the Lorenz–Stenflo equations and which admit chaotic trajectories. The results of this investigation should be useful for understanding the linear and nonlinear properties of electromagnetic waves that are generated by sheared plasma flows in magnetized plasmas.

Bifurcation behavior of the generalized Lorenz equations at large rotation numbers

The bifurcation structure and periodic orbits of the Lorenz–Stenflo equations at large rotation numbers are given. It is shown that rotation can lead to a much richer dynamical behavior than that of the original Lorenz system and can be used to control or modify the latter’s chaos behavior. Orbits with new topology arising from the merging and splitting of different periodic windows are observed. Abrupt changes in the one-dimensional map are pointed out and studied in terms of the interaction of the interior and exterior boundaries.