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Turbulence in an incompressible fluid with and without a magnetic field as well as moderately compressible MHD turbulence are compared. For the magnetohydrodynamic (MHD) models the probability distribution functions of the velocity…

Astrophysics · Physics 2007-05-23 Nicholas Hall , G. Kowal , A. Lazarian , Jungyeon Cho

The role of magnetic helicity is investigated in kinetic Alfv\'en wave and oblique whistler turbulence in presence of a relatively intense external magnetic field $b_0 {\bf e_\parallel}$. In this situation, turbulence is strongly…

Solar and Stellar Astrophysics · Physics 2019-02-20 S. Galtier , R. Meyrand

Current analytical and numerical modelling suggest the existence of ubiquitous thin current sheets in the corona that could explain the observed heating requirements. On the other hand, new high resolution observations of the corona…

Solar and Stellar Astrophysics · Physics 2015-06-19 P. Antolin , T. Yokoyama , T. Van Doorsselaere

This two-part review summarizes interstellar turbulence and its implications. The first part begins with diagnostics and energy sources. Turbulence theory is considered in detail, including the basic fluid equations, solenoidal and…

Astrophysics · Physics 2008-11-26 Bruce G. Elmegreen , John Scalo

Various approaches to estimate turbulent transport coefficients from numerical simulations of hydromagnetic turbulence are discussed. A quantitative comparison between the averaged magnetic field obtained from a specific three-dimensional…

Astrophysics · Physics 2009-11-07 Axel Brandenburg , Dmitry Sokoloff

Plasma flows with an MHD-like turbulent inertial range, such as the solar wind, require a generalization of General Magnetic Reconnection (GMR) theory. We introduce the slip-velocity source vector, which gives the rate of development of…

Solar and Stellar Astrophysics · Physics 2015-07-15 Gregory L. Eyink

Solar-type stars exhibit a rich variety of magnetic activity. Seeking to explore the convective origins of this activity, we have carried out a series of global 3D magnetohydrodynamic (MHD) simulations with the anelastic spherical harmonic…

Solar and Stellar Astrophysics · Physics 2015-06-12 Nicholas J. Nelson , Benjamin P. Brown , A. Sacha Brun , Mark S. Miesch , Juri Toomre

We present a new scale decomposition method to investigate turbulence in wavenumber-frequency space. Using 3D magnetohydrodynamic turbulence simulations, we show that magnetic fluctuations with time scales longer than the nonlinear time…

Solar and Stellar Astrophysics · Physics 2024-12-02 Giuseppe Arrò , Hui Li , William H. Matthaeus

Magnetized turbulence is ubiquitous in many astrophysical and terrestrial systems but no complete, uncontested theory even in the simplest form, magnetohydrodynamics (MHD), exists. Many theories and phenomenologies focus on the joint…

Plasma Physics · Physics 2021-03-24 Philipp Grete , Brian W. O'Shea , Kris Beckwith

Flaring release of magnetic energy in solar corona is only possible if the magnetic field deviates from a potential one. We show that the linear MHD modes excited on top of the non-potential magnetic field possess a nonzero kinetic…

Solar and Stellar Astrophysics · Physics 2015-06-12 Gregory D. Fleishman , Igor N. Toptygin

We explore the phenomenon of the recently discovered inverse transfer of energy from small to large scales in decaying magnetohydrodynamical turbulence by Brandenburg et al. (2015) even for nonhelical magnetic fields. For this investigation…

Cosmology and Nongalactic Astrophysics · Physics 2017-11-15 Johannes Reppin , Robi Banerjee

We clarify how magnetic reconnection can be derived from magnetohydrodynamics (MHD) equations in a way that is easily understandable to university students. The essential mechanism governing the time evolution of the magnetic field is…

Plasma Physics · Physics 2014-03-18 Tohru Tashiro , Wakako Kakuta

We consider strongly stratified forced turbulence in a plane-parallel layer with helicity and corresponding large-scale dynamo action in the lower part and non-helical turbulence in the upper. The magnetic field is found to develop strongly…

Solar and Stellar Astrophysics · Physics 2016-05-23 Sarah Jabbari , Axel Brandenburg , Dhrubaditya Mitra , Nathan Kleeorin , Igor Rogachevskii

We present a new theoretical picture of magnetically dominated, decaying turbulence in the absence of a mean magnetic field. We demonstrate that such turbulence is governed by the reconnection of magnetic structures, and not by ideal…

Fluid Dynamics · Physics 2021-10-13 David N. Hosking , Alexander A. Schekochihin

Magnetic reconnection is commonly considered as a mechanism of solar (eruptive) flares. A deeper study of this scenario reveals, however, a number of open issues. Among them is the fundamental question, how the magnetic energy is…

Solar and Stellar Astrophysics · Physics 2015-03-17 Miroslav Bárta , Jörg Büchner , Marian Karlický , Jan Skála

One of the most important predictions in magnetohydrodynamics (MHD) is that in the presence of a uniform magnetic field $\textbf{b}_{0}$ a transition from weak to strong wave turbulence should occur when going from large to small…

Fluid Dynamics · Physics 2016-03-23 Romain Meyrand , Sebastien Galtier , Khurom H. Kiyani

Numerical simulations of the 3D MHD-equations that describe rotating magnetoconvection in a Cartesian box have been performed using the code NIRVANA. The characteristics of averaged quantities like the turbulence intensity and the turbulent…

Earth and Planetary Astrophysics · Physics 2015-03-13 A. Giesecke

Fast magnetic reconnection powers explosive events throughout the universe, from gamma-ray bursts to solar flares. Despite its importance, the onset of astrophysical fast reconnection is the subject of intense debate and remains an open…

Solar and Stellar Astrophysics · Physics 2020-02-07 L. P. Chitta , A. Lazarian

Recent advances in understanding of the basic properties of compressible Magnetohydrodynamic (MHD) turbulence call for revisions of some of the generally accepted concepts. First, MHD turbulence is not so messy as it is usually believed. In…

Astrophysics · Physics 2009-11-10 A. Lazarian , J. Cho

Supersonic turbulence is believed to be at the heart of star formation. We have performed smoothed particle magnetohydrodynamics (SPMHD) simulations of the small-scale dynamo amplification of magnetic fields in supersonic turbulence. The…

Instrumentation and Methods for Astrophysics · Physics 2016-06-03 Terrence S. Tricco , Daniel J. Price , Christoph Federrath