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Magnetic flux tubes such as those in the solar corona are subject to a number of instabilities. Important among them is the kink instability which plays a central part in the nanoflare theory of coronal heating, and for this reason in…
We present global 3D MHD simulations of disks of gas and solids, aiming at developing models that can be used to study various scenarios of planet formation and planet-disk interaction in turbulent accretion disks. A second goal is to show…
Threads are the main constituents of prominences and are subjected to oscillations that might be interpreted as MHD waves. Moreover, the Kelvin-Helmholtz instability (KHI) has been reported in prominences. Both waves and KHI may affect the…
We formulate a coarse-graining approach to the dynamics of magnetohydrodynamic (MHD) fluids at a continuum of length-scales. In this methodology, effective equations are derived for the observable velocity and magnetic fields…
It has been proposed that the million degree temperature of the corona is due to the combined effect of barely-detectable energy releases, so called nanoflares, that occur throughout the solar atmosphere. Alas, the nanoflare density and…
Context. Photospheric motions shuffle the footpoints of the strong axial magnetic field that threads coronal loops giving rise to turbulent nonlinear dynamics characterized by the continuous formation and dissipation of field-aligned…
Outflows perpendicular to the guide field are believed to be a possible signature of magnetic reconnection in the solar corona and specifically a way to detect the occurrence of ubiquitous small-angle magnetic reconnection. The aim of this…
It was once thought that all coronal loops are in static equilibrium, but observational and modeling developments over the past decade have shown that this is clearly not the case. It is now established that warm (~1 MK) loops observed in…
Kink magnetohydrodynamic (MHD) waves are frequently observed in various magnetic structures of the solar atmosphere. They may contribute significantly to coronal heating and could be used as a tool to diagnose the solar plasma. In this…
Turbulent motion driven by the magnetorotational instability (MRI) is believed to provide an anomalous viscosity strong enough to account for observed accretion rates in protostellar accretion disks. In the first of two papers, we perform…
We numerically investigate the driving of MHD turbulence by gravitational contraction using simulations of an initially spherical, magnetically supercritical cloud core with initially transonic and trans-Alfv\'enic turbulence. We perform a…
Coronal mass ejections (CMEs) are powerful drivers of space weather, with magnetic flux ropes (MFRs) widely regarded as their primary precursors. However, the variation in reconnection flux during the evolution of MFR during CME eruptions…
Magnetohydrodynamics (MHD) is invoked to address turbulent fluctuations in a variety of astrophysical systems. MHD turbulence in nature is often anisotropic and imbalanced, in that Alfvenic fluctuations moving in opposite directions along…
Transverse oscillations of coronal loops are often observed and have been theoretically interpreted as kink magnetohydrodynamic (MHD) modes. Numerical simulations by Terradas et al. (2008, ApJ 687, L115) suggest that shear flows generated…
In addition to buoyancy- and magnetic tension-driven instabilities, magnetic flux rings are also susceptible to an instability induced by the hydrodynamic drag force. We investigate the influence of the toroidal shape and equilibrium…
I present a review of incompressible magnetohydrodynamic (MHD) turbulence in a strongly magnetised plasma. The approach is phenomenological even where a more rigorous theory is available, so that a reader armed with paper, pencil and some…
Coronal loops, constituting the basic building blocks of the active Sun, serve as primary targets to help understand the mechanisms responsible for maintaining multi-million Kelvin temperatures in the solar and stellar coronae. Despite…
Recent observations have established that the magnetosphere is a system of natural complexity. The co-existence of multi-scale structures such as auroral arcs, turbulent convective flows, and scale-free distributions of energy perturbations…
We present an alternative model of coronal-loop oscillations which considers that the waves are trapped in a 2D waveguide formed by the entire arcade of field lines. This differs from the standard 1D model which treats the waves as the…
The MHD flow driven by a travelling magnetic field (TMF) in an annular channel is investigated numerically. For sufficiently large magnetic Reynolds number Rm, or if a large enough pressure gradient is externally applied, the system…