Coherence and Intermittency of Electron Density in Small-Scale Interstellar Turbulence

Abstract

Spatial intermittency in decaying kinetic Alfven wave turbulence is investigated to determine if it produces non Gaussian density fluctuations in the interstellar medium. Non Gaussian density fluctuations have been inferred from pulsar scintillation scaling. Kinetic Alfven wave turbulence characterizes density evolution in magnetic turbulence at scales near the ion gyroradius. It is shown that intense localized current filaments in the tail of an initial Gaussian probability distribution function possess a sheared magnetic field that strongly refracts the random kinetic Alfven waves responsible for turbulent decorrelation. The refraction localizes turbulence to the filament periphery, hence it avoids mixing by the turbulence. As the turbulence decays these long-lived filaments create a non Gaussian tail. A condition related to the shear of the filament field determines which fluctuations become coherent and which decay as random fluctuations. The refraction also creates coherent structures in electron density. These structures are not localized. Their spatial envelope maps into a probability distribution that decays as density to the power -3. The spatial envelope of density yields a Levy distribution in the density gradient.

31 pages, 3 figures. Replacement contains short additions to Secs. 6 and 7

References in corpus (6)

• Measurement of the electric fluctuation spectrum of magnetohydrodynamic turbulence
• Multifrequency Observations of Radio Pulse Broadening and Constraints on Interstellar Electron Density Microstructure
• Astrophysical Gyrokinetics: Basic Equations and Linear Theory
• Levy model for interstellar scintillations
• Non-Gaussian Radio-Wave Scattering in the Interstellar Medium
• Small-scale dissipative structures of diffuse ISM turbulence: I- CO diagnostics

Cited by in corpus (7)

• Magnetic Fields from QCD Phase Transitions
• Polarized Gravitational Waves from Cosmological Phase Transitions
• Kinetic Turbulence in Astrophysical Plasmas: Waves and/or Structures?
• Atomic and Ionized Microstructures in the Diffuse Interstellar Medium
• Phase Transition Generated Cosmological Magnetic Field at Large Scales
• Damping of Electron Density Structures and Implications for Interstellar Scintillation
• Exposing the plural nature of molecular clouds : Extracting filaments and the CIB against the true scale-free interstellar medium