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We explore the effect of magnetic fields on the vertical distribution and multiphase structure of the supernova-driven interstellar medium (ISM) in simulations that admit dynamo action. As the magnetic field is amplified to become dynamically significant, gas becomes cooler and its distribution in the disc becomes more homogeneous. We attribute this to magnetic quenching of vertical velocity, which leads to a decrease in the cooling length of hot gas. A non-monotonic vertical distribution of the large-scale magnetic field strength, with the maximum at |z| $\approx$ 300 pc causes a downward pressure gradient below the maximum which acts against outflow driven by SN explosions, while it provides pressure support above the maximum., Comment: 10 pages, 10 figures

One means of producing a 3D current in a circular tank is by using groups of conditioned axial flow impellers arranged around the perimeter to collectively create a sea representative bulk flow in a laboratory setting. Unfortunately to achieve the required bulk flow neighbouring impellers have to operate at different speeds resulting in steps in the plan view velocity profile. Therefore the underlying situation that governs tank behaviour is that of two fluid streams at different speeds combining, leading to a turbulent mixing layer which then dissipates and develops. Here a simulation of this flow is created using a 2D Reynolds Averaged Navier-Stokes method and then validated with physical experiments. The implications for accuracy and computational costs of various turbulence models, boundary conditions setups, and geometry representations are assessed. These findings are then used to produce a simplified 2D numerical model of the plan view flows in a 3D test tank which is then employed to demonstrate how a satisfactory device test zone might be generated from groups of stepped inputs. This finding helps prove that a combined current and wave tank can be created using the described configuration with the model providing a useful means of testing control scenarios. (C) 2014 Elsevier Ltd. All rights reserved.

An unusually strong and prolonged stratospheric sudden warming (SSW) in January 2006 was the first major SSW for which globally distributed long-lived trace gas data are available covering the upper troposphere through the lower mesosphere. We use Aura Microwave Limb Sounder (MLS), Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) data, the SLIMCAT Chemistry Transport Model (CTM), and assimilated meteorological analyses to provide a comprehensive picture of transport during this event. The upper tropospheric ridge that triggered the SSW was associated with an elevated tropopause and layering in trace gas profiles in conjunction with stratospheric and tropospheric intrusions. Anomalous poleward transport (with corresponding quasi-isentropic troposphere-to-stratosphere exchange at the lowest levels studied) in the region over the ridge extended well into the lower stratosphere. In the middle and upper stratosphere, the breakdown of the polar vortex transport barrier was seen in a signature of rapid, widespread mixing in trace gases, including CO, H2O, CH4 and N2O. The vortex broke down slightly later and more slowly in the lower than in the middle stratosphere. In the middle and lower stratosphere, small remnants with trace gas values characteristic of the pre-SSW vortex lingered through the weak and slow recovery of the vortex. The upper stratospheric vortex quickly reformed, and, as enhanced diabatic descent set in, CO descended into this strong vortex, echoing the fall vortex development. Trace gas evolution in the SLIMCAT CTM agrees well with that in the satellite trace gas data from the upper troposphere through the middle stratosphere. In the upper stratosphere and lower mesosphere, the SLIMCAT simulation does not capture the strong descent of mesospheric CO and H2O values into the reformed vortex; this poor CTM performance in the upper stratosphere and lower mesosphere results primarily from biases in the diabatic descent in assimilated analyses.