The preceding chapter discussed the microscopic, kinetic and two-fluid decsriptions of a plasma. But we would actually like a simpler model — one that would include most of the macroscopic properties of a plasma in a “one-fluid” model. The simplest such model is magnetohydrodynamics (MHD), which is a combination of a one-fluid (hydrodynamic-type plus Lorentz force effects) model for the plasma ...

Magnetohydrodynamics (MHD), the science of the motion of an electrically conducting fluid in the presence of a magnetic field, consists essentially of the interaction between the fluid velocity and the magnetic field. Electric currents induced in the fluid as a result of its motion modify the field; at the same time their flow in the magnetic field leads to mechanical forces which modify the mo...

We propose collisionless damping of fast MHD waves as an important mechanism for the heating and acceleration of winds from rotating stars. Stellar rotation causes magnetic field lines anchored at the surface to form a spiral pattern and magneto-rotational winds can be driven. If the structure is a magnetically dominated, fast MHD waves generated at the surface can propagate almost radially out...

Background Due to the Magneto-Hydro-Dynamic (MHD) effect, blood flow within the MRI’s magnetic field (B0) produces a large voltage during the S-T cardiac segment [1]. The peak MHD voltage (VMHD) can be comparable, in higher-field MRIs, to the R-wave amplitude of the real Electrocardiogram (ECGreal), so that VMHD reduces ECG-gating reliability and prevents ischemia-monitoring during cardiac imag...

The existence and uniqueness of solutions to the two-dimensional stochastic magneto-hydrodynamic system is established in the presence of either a multiplicative noise or an additive fractional Brownian noise. The method of monotonicity is employed when the noise is multiplicative. In the case of a fractional Brownian noise, a unique mild solution of the system is established under suitable con...

Winds from accretion disks have been proposed as the driving source for precessing jets and extreme bipolar morphologies in Planetary Nebulae (PNe) and proto-PNe (pPNe). In this paper we address the applicability of self-consistent MHD disk wind models to PNe and pPNe. We first review the basic features of magneto-centrifugal launching disk wind models adapting results from previously published...

We present two-dimensional, cylindrically symmetric simulations of hydrodynamic and magnetohydrodynamic (MHD) wide-angle winds interacting with a collapsing environment. These simulations have direct relevance to young stellar objects (YSOs). The results may also be of use in the study of collimated outflows from proto-planetary and planetary nebulae. We study a range of wind configurations con...

A linear deformation, by a magneto-rotational instability, of the transition suface between an outer Shakura-Sunyaev-type standard disk (SSD) and inner advection-dominated accretion flows (ADAF) is examined. The transition is assumed to be a discontinuous plane where a low-temperature, high-density gas is jointed to a high-temperature, low-density gas. No mass flow through the surface is consid...

When the ion mean free path much exceeds the Larmor radius in a plasma, the viscous stress tensor is altered dramatically, and depends only upon quantities measured along the field lines. This regime corresponds to typical interstellar medium conditions in galaxies and protogalaxies, even if the magnetic field is extremely weak with negligible pressure and tension forces. Despite the fact that ...

Line widths derived from observational data obtained by SUMER onboard SOHO in August 1996 at disk center and at the limb are used to confront those derived via assuming Alfvén and/or magneto-acoustic wave heating. The observational data clearly shows a center-to-limb variation in the upper chromospheric and transition region lines, with only a marginal difference in the coronal lines in the sen...