http://arxiv.org/abs/1407.6579
We present 2D adiabatic magnetohydrodynamic (MHD) simulations of a shock interacting with groups of two or three cylindrical clouds. We study how the presence of a nearby cloud influences the dynamics of this interaction, and explore the resulting differences and similarities in the evolution of each cloud. The understanding gained from this small-scale study will help to interpret the behaviour of systems with many 10’s or 100’s of clouds.
We observe a wide variety of behaviour in the interactions studied, which is dependent on the initial positions of the clouds and the orientation and strength of the magnetic field. We find: i) some clouds are stretched along their field-lines, whereas others are confined by their field-lines; ii) upstream clouds may accelerate past downstream clouds (though magnetic tension can prevent this); iii) clouds may also change their relative positions transverse to the direction of shock propagation as they “slingshot” past each other; iv) downstream clouds may be offered some protection from the oncoming flow as a result of being in the lee of an upstream cloud; v) the cycle of cloud compression and re-expansion is generally weaker when there are nearby neighbouring clouds; vi) the plasma $\beta$ in cloud material can vary rapidly as clouds collide with one another, but low values of $\beta$ are always transitory.
This work is relevant to studies of multi-phase regions, where fast, low-density gas interacts with dense clouds, such as in circumstellar bubbles, supernova remnants, superbubbles and galactic winds.
R. Aluzas, J. Pittard, S. Falle, et. al.
Fri, 25 Jul 14
10/57
Comments: 24 pages, 30 figures. Accepted for publication in MNRAS