Astrophysical Hydromagnetic Turbulence (original) (raw)
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Lecture Notes in Physics, 2003
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Magnetohydrodynamic Turbulence in the Solar Wind
Annual Review of Astronomy and Astrophysics, 1995
Recent work in describing the solar wind as an MHD turbulent fluid has shown that the magnetic fluctuations are adequately described as time stationary and to some extent as spatially homogeneous. Spectra of the three rugged invariants of incompressible MHD are the principal quantities used to characterize the velocity and magnetic field fluctuations. Unresolved issues concerning the existence of actively developing turbulence are discussed. INTRODUCTION To describe a fluid system as turbulent is to say that the dynamical fluid variables exhibit complex and essentially non-reproducible behavior as a function of time. This is generally due to the presence of nonlinearities in the fluid equations which strongly couple a large number of degrees of freedom. Turbulent systems are usually very far from equilibrium states for which detailed analytically tractable theories might exist. By all appearances, the solar wind plasma flow and the interplanetary magnetic field carried along with it are such a turbulent system. In the zero momentum frame, the magnetic and velocity field fluctuations are energetically comparable to the mean magnetic field over length scales of order I AU and display the type of complicated behavior expected of turbulence. velocity and magnetic fields in magnetohydrodynamie turbulence, EOS,
Space Science Reviews, 2009
Astrophysical fluids, including interstellar and interplanetary medium, are magnetized and turbulent. Their appearance, evolution, and overall properties are determined by the magnetic turbulence that stirs it. We argue that examining magnetic turbulence at a fundamental level is vital to understanding many processes. A point that frequently escapes the attention of researchers is that magnetic turbulence cannot be confidently understood only using "brute force" numerical approaches. In this review we illustrate this point on a number of examples, including intermittent heating of plasma by turbulence, interactions of turbulence with cosmic rays and effects of turbulence on the rate of magnetic reconnection. We show that the properties of magnetic turbulence may vary considerably in various environments, e.g. imbalanced turbulence in solar wind differs from balanced turbulence and both of these differ from turbulence in partially ionized gas. Appealing for the necessity of more observational data on magnetic fields, we discuss a possibility of studying interplanetary turbulence using alignment of Sodium atoms in the tail of comets.
Magnetohydrodynamic Turbulence as a Foreground for Cosmic Microwave Background Studies
The Astrophysical Journal, 2002
Measurements of intensity and polarization of diffuse Galactic synchrotron emission as well as starlight polarization reveal power law spectra of fluctuations. We show that these fluctuations can arise from magnetohydrodynamic (MHD) turbulence in the Galactic disk and halo. To do so we take into account the converging geometry of lines of sight for the observations when the observer is within the turbulent volume. Assuming that the intensity of turbulence changes along the line of sight, we get a reasonable fit to the observed synchrotron data. As for the spectra of polarized starlight we get a good fit to the observations taking into account the fact that the observational sample is biased toward nearby stars.
COSMIC-RAY CURRENT-DRIVEN TURBULENCE AND MEAN-FIELD DYNAMO EFFECT
The Astrophysical Journal, 2012
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