An analysis is made for transient Magnetohydrodynamic (MHD) flow of two immiscible fluids thorough a horizontal channel. The flow above the interface is assumed to be electrically conducting while the other fluid and the channel walls are assumed to be electrically insulating. The partial differential equations governing the flow are solved analytically using two-term periodic and non-periodic ...

Context. The highly dynamical, complex nature of the solar atmosphere naturally implies the presence of waves in a topologically varied magnetic environment. Here, the interaction of waves with topological features such as null points is inevitable and potentially important for energetics. The low resistivity of the solar coronal plasma implies that non-magnetohydrodynamic (MHD) effects should ...

The three-dimensional incompressible magnetohydrodynamic equations with stochastic external forces are considered. First, the existence and uniqueness of local strong solution to the stochastic magnetohydrodynamic equations are proved when the external forces satisfy some conditions. The proof is based on the contraction mapping principle, stopping time and stochastic estimates. The strong solu...

The linear stability of magnetohydrodynamic Taylor-Couette flows in axially unbounded cylinders is considered for magnetic Prandtl number unity. Magnetic background fields varying from purely axial to purely azimuthal are imposed, with a general helical field parametrized by β=B(ϕ)/B(z). We map out the transition from the standard magnetorotational instability (MRI) for β=0 to the nonaxisymmetr...

I consider the nonaxisymmetric linear theory of an isothermal magnetohydrodynamic (MHD) shear flow. The analysis is performed in the shearing box, a local model appropriate for a thin disk geometry. Linear perturbations in this model can be decomposed in terms of shearing waves (shwaves), which appear spatially as plane waves in a frame comoving with the shear. The time dependence of these wave...

WeakMHD turbulence consists of waves that propagate along magnetic field lines, in both directions. When two oppositely directed waves collide, they distort each other, without changing their respective energies. Each wave suffers many collisions before cascading; by contrast, in strong MHD turbulence, waves cascade on the same timescale at which they collide. ‘‘ Imbalance ’’ means that more en...

The theory of magnetically accelerated outtows and jets from accretion disks is reviewed at an introductory level, with special attention to problem areas like the launching conditions of the ow at the disk surface, stability of the magnetic eld, and collimation mechanisms. This text will appear in R. 1.1 Introduction: the case for magnetic acceleration Narrow, high speed outtows (jets) and les...