Nonaxisymmetric anisotropy of solar wind turbulence as a direct test for models of magnetohydrodynamic turbulence.

Single point spacecraft observations of the turbulent solar wind flow exhibit a characteristic nonaxisymmetric anisotropy that depends sensitively on the perpendicular power spectral exponent. We use this nonaxisymmetric anisotropy as a function of wave vector direction to test models of MHD turbulence. Using Ulysses magnetic field observations in the fast, quiet polar solar wind we find that the Goldreich-Sridhar model of MHD turbulence is not consistent with the observed anisotropy, whereas the observations are well reproduced by the "slab+2D" model.

Scale-free texture of the fast solar wind.

The higher-order statistics of magnetic field magnitude fluctuations in the fast quiet solar wind are quantified systematically, scale by scale. We find a single global non-Gaussian scale-free behavior from minutes to over 5 h. This spans the signature of an inertial range of magnetohydrodynamic turbulence and a ~1/f range in magnetic field components.

Nonaxisymmetric anisotropy of solar wind turbulence.

A key prediction of turbulence theories is frame-invariance, and in magnetohydrodynamic (MHD) turbulence, axisymmetry of fluctuations with respect to the background magnetic field. Paradoxically the power in fluctuations in the turbulent solar wind are observed to be ordered with respect to the bulk macroscopic flow as well as the background magnetic field. Here, nonaxisymmetry across the inertial and dissipation ranges is quantified using in situ observations from Cluster.

Lagrangian frequency spectrum as a diagnostic for magnetohydrodynamic turbulence dynamics.

For the phenomenological description of magnetohydrodynamic turbulence competing models exist, e.g., Boldyrev [Phys.

Gravitational radiation from primordial helical magnetohydrodynamic turbulence.

We consider gravitational waves (GWs) generated by primordial inverse-cascade helical magneto-hydrodynamical (MHD) turbulence produced by bubble collisions at the electroweak phase transitions (EWPT). Compared to the unmagnetized EWPT case, the spectrum of MHD-turbulence-generated GWs peaks at lower frequency with larger amplitude and can be detected by the proposed Laser Interferometer Space Antenna.

Excitation and conversion of electromagnetic waves in pulsar magnetospheres.

We demonstrate that nonlinear decay of obliquely propagating Langmuir waves into Langmuir and Alfvén waves (L --> L' + A) is possible in a one-dimensional, highly relativistic, streaming pair plasma. Such a plasma may be in the magnetospheres of pulsars. It is shown that the characteristic frequency of generated Alfvén waves is much less than the frequency of Langmuir waves and may be consistent with the observational data on the radio emission of pulsars.

Scaling law of plasma turbulence with nonconservative fluxes.

It is shown that in the presence of anisotropic kinetic dissipation existence of the scale invariant power law spectrum of plasma turbulence is possible. The obtained scale invariant spectrum is not associated with the constant flux of any physical quantity. Application of the model to the high frequency part of the solar wind turbulence is discussed.

Polarized cosmological gravitational waves from primordial helical turbulence.

We show that helical turbulence produced during a first-order phase transition generates circularly polarized cosmological gravitational waves (GWs). The characteristic frequency of these GWs for an extreme case of the phase transition model is around 10(-3)-10(-2) Hz with an energy density parameter as high as 10(-12)-10(-11). The possibility of detection is briefly discussed.

Discrete coherent amplification of oscillations by nonresonant forcing.

A new mechanism of generation of oscillations in a linear forced oscillatory system is found. Natural oscillations may be generated at a "sharp" pulse (rapid variation) of the natural frequency. In this process oscillations are generated by nonresonant forcing, e.