A theoretical mean field closure for Hall magnetohydrodynamics (Hall-MHD) is developed to investigate magnetic field generation through dynamo processes in low electron density astrophysical systems. We show that by modifying the dynamics of microscopic flows, the Hall currents could have a profound impact on the generation of macroscopic magnetic fields. As an illustrative example, we show how...

Particle heating in advection-dominated accretion flows (ADAFs) by nonlinear MHD (Alfvénic) turbulence is investigated. Such turbulence with highly-fluctuating magnetic fields, B̃ ∼ B0, is believed to be naturally produced by the magnetic shearing instability near the nonlinear saturation. It is shown that the energy is dissipated in the parallel cascade, which occurs due to nonlinear compressib...

Scientific context Magnetic fields are important dynamically in a variety of situations in geophysics and astrophysics. Numerous observations are appearing, e.g. thanks to remote sensing and in particular to the CLUSTER ensemble of 4 satellites, allowing for an estimation of fields and of their derivatives in the Solar Wind close environment. In the magnetohydrodynamic (MHD) approximation valid...

By a systematic method we construct general classes of exact and selfconsistent axisymmetric MHD solutions describing flows which originate at the near environment of a central gravitating astrophysical object. The unifying scheme contains two large groups of exact MHD outflow models, (I) meridionally self-similar ones with spherical critical surfaces and (II) radially self-similar models with ...

Accretion flows onto underluminous black holes, such as Sagittarius A* at the center of our galaxy, are dilute (mildly collisional to highly collisionless), optically thin, and radiatively inefficient. Therefore, the accretion properties of such dilute flows are expected to be modified by their large viscosities and thermal conductivities. Second, turbulence within these systems needs to transp...

We propose that inward, subsonic flows arise from the local dissipation of turbulent motions in molecular clouds. Such “turbulent cooling flows” may account for recent observations of spatially extended inward motions toward dense cores. These pressure-driven flows may arise from various types of turbulence and dissipation mechanisms. For the example of MHD waves and turbulence damped by ion-ne...

In this work, the gas-kinetic method (GKM) is enhanced with resistive and Hall magnetohydrodynamics (MHD) effects. Known as MGKM (for MHD–GKM), this approach incorporates additional source terms to the momentum and energy conservation equations and solves the magnetic field induction equation. We establish a verification protocol involving numerical solutions to the one-dimensional (1D) shock t...

The influence of a stationary mass flow on driven resonant MHD waves is studied for incoming slow and fast magnetosonic waves with frequencies in the slow and the Alfvén continua. In addition to the classic resonant absorption already present in a static plasma, driven resonant waves can also undergo overreflection. Depending on the strength of the equilibrium flow a variety of resonant MHD wav...

In this paper we show how the Smoothed Particle Hydrodynamics (SPH) equations for ideal Magnetohydrodynamics (MHD) can be written in conservation form with the positivity of the dissipation guaranteed. We call the resulting algorithm Smoothed Particle Magnetohydrodynamics (SPMHD). The equations appear to be accurate, robust and easy to apply and do not suffer from the instabilities known to exi...

We present numerical simulations of electron magnetohydrodynamic (EMHD) and electron reduced MHD (ERMHD) turbulence. Comparing scaling relations, we find that both EMHD and ERMHD turbulence show similar spectra and anisotropy. We develop new techniques to study anisotropy of EMHD turbulence. Our detailed study of anisotropy of EMHD turbulence supports our earlier result of k‖ ∝ k ⊥ scaling, whe...