464 research outputs found
An Experimental Platform for Pulsed-Power Driven Magnetic Reconnection
We describe a versatile pulsed-power driven platform for magnetic
reconnection experiments, based on exploding wire arrays driven in parallel
[Suttle, L. G. et al. PRL, 116, 225001]. This platform produces inherently
magnetised plasma flows for the duration of the generator current pulse (250
ns), resulting in a long-lasting reconnection layer. The layer exists for long
enough to allow evolution of complex processes such as plasmoid formation and
movement to be diagnosed by a suite of high spatial and temporal resolution
laser-based diagnostics. We can access a wide range of magnetic reconnection
regimes by changing the wire material or moving the electrodes inside the wire
arrays. We present results with aluminium and carbon wires, in which the
parameters of the inflows and the layer which forms are significantly
different. By moving the electrodes inside the wire arrays, we change how
strongly the inflows are driven. This enables us to study both symmetric
reconnection in a range of different regimes, and asymmetric reconnection.Comment: 14 pages, 9 figures. Version revised to include referee's comments.
Submitted to Physics of Plasma
Formation and Structure of a Current Sheet in Pulsed-Power Driven Magnetic Reconnection Experiments
We describe magnetic reconnection experiments using a new, pulsed-power
driven experimental platform in which the inflows are super-sonic but
sub-Alfv\'enic.The intrinsically magnetised plasma flows are long lasting,
producing a well-defined reconnection layer that persists over many
hydrodynamic time scales.The layer is diagnosed using a suite of high
resolution laser based diagnostics which provide measurements of the electron
density, reconnecting magnetic field, inflow and outflow velocities and the
electron and ion temperatures.Using these measurements we observe a balance
between the power flow into and out of the layer, and we find that the heating
rates for the electrons and ions are significantly in excess of the classical
predictions. The formation of plasmoids is observed in laser interferometry and
optical self-emission, and the magnetic O-point structure of these plasmoids is
confirmed using magnetic probes.Comment: 14 pages, 12 figures. Accepted for publication in Physics of Plasma
Morphology of Shocked Lateral Outflows in Colliding Hydrodynamic Flows
Supersonic interacting flows occurring in phenomena such as protostellar jets
give rise to strong shocks, and have been demonstrated in several laboratory
experiments. To study such colliding flows, we use the AstroBEAR AMR code to
conduct hydrodynamic simulations in three dimensions. We introduce variations
in the flow parameters of density, velocity, and cross sectional radius of the
colliding flows %radius in order to study the propagation and conical shape of
the bow shock formed by collisions between two, not necessarily symmetric,
hypersonic flows. We find that the motion of the interaction region is driven
by imbalances in ram pressure between the two flows, while the conical
structure of the bow shock is a result of shocked lateral outflows (SLOs) being
deflected from the horizontal when the flows are of differing cross-section
Cooling and Instabilities in Colliding Radiative Flows with Toroidal Magnetic Fields
We report on the results of a simulation based study of colliding magnetized
plasma flows. Our set-up mimics pulsed power laboratory astrophysical
experiments but, with an appropriate frame change, are relevant to
astrophysical jets with internal velocity variations. We track the evolution of
the interaction region where the two flows collide. Cooling via radiative loses
are included in the calculation. We systematically vary plasma beta ()
in the flows, the strength of the cooling () and the exponent
() of temperature-dependence of the cooling function. We find that for
strong magnetic fields a counter-propagating jet called a "spine" is driven by
pressure from shocked toroidal fields. The spines eventually become unstable
and break apart. We demonstrate how formation and evolution of the spines
depends on initial flow parameters and provide a simple analytic model that
captures the basic features of the flow.Comment: 14 pages, 16 figures. Submitted to MNRA
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