arXiv subjects

M. G. Haines

Publications and source records attributed to M. G. Haines.

5 recordsLinked to original sources

arXiv2026

Observation of Self-Similarity in the Magnetic Fields Generated by the Ablative Nonlinear Rayleigh-Taylor Instability

Magnetic fields generated by the nonlinear Rayleigh-Taylor growth of laser-seeded three-dimensional broadband perturbations were measured in laser-accelerated planar targets using ultrafast proton radiography. The experimental data show self-similar behavior in the growing cellular magnetic field structures. These observations are consistent with a bubble competition and merger model that predicts the time evolution of the number and size of the bubbles, linking the cellular magnetic field structures with the Rayleigh-Taylor bubble and spike growth.

physics.plasm-ph↗

arXiv2005

X-point collapse and saturation in the nonlinear tearing mode reconnection

We study the nonlinear evolution of the resistive tearing mode in slab geometry in two dimensions. We show that, in the strongly driven regime (large Delta'), a collapse of the X-point occurs once the island width exceeds a certain critical value ~1/Delta'. A current sheet is formed and the reconnection is exponential in time with a growth rate ~eta^1/2, where eta is the resistivity. If the aspect ratio of the current sheet is sufficiently large, the sheet can itself become tearing-mode unstable, giving rise to secondary islands, which then coalesce with the original island. The saturated state depends on the value of Delta'. For small Delta', the saturation amplitude is ~Delta' and quantitatively agrees with the theoretical prediction. If Delta' is large enough for the X-point collapse to have occured, the saturation amplitude increases noticeably and becomes independent of Delta'.

physics.plasm-ph↗

arXiv2004

Fast and slow nonlinear tearing mode reconnection

This is a brief account of our numerical study of the tearing mode reconnection. We demonstrate two main points. First, we show that, given sufficiently small resistivity, the Rutherford regime always exists; larger values of Delta' require smaller values of resistivity. Rutherford's negligible-inertia assumption is validated and the asymptotically linear dependence of the time derivative of the island width on the resistivity and Delta' is confirmed. Second, we find that, at large Delta', the Rutherford regime is followed by a nonlinear stage of fast growth linked to X-point collapse and formation of a current sheet. This causes the reconnection to become Sweet-Parke (SP) like. The signature resistivity^{1/2} scaling of the effective island growth rate is, indeed, found in this nonlinear stage. The SP stage culminates in the saturation of the mode, which can, thus, be achieved much faster than via Rutherford regime.

physics.plasm-ph↗

arXiv2004

Jet Deflection via Cross winds: Laboratory Astrophysical Studies

We present new data from High Energy Density (HED) laboratory experiments designed to explore the interaction of a heavy hypersonic radiative jet with a cross wind. The jets are generated with the MAGPIE pulsed power machine where converging conical plasma flows are produced from a cylindrically symmetric array of inclined wires. Radiative hypersonic jets emerge from the convergence point. The cross wind is generated by ablation of a plastic foil via soft-X-rays from the plasma convergence region. Our experiments show that the jets are deflected by the action of the cross wind with the angle of deflection dependent on the proximity of the foil. Shocks within the jet beam are apparent in the data. Analysis of the data shows that the interaction of the jet and cross wind is collisional and therefore in the hydro-dynamic regime. MHD plasma code simulations of the experiments are able to recover the deflection behaviour seen in the experiments. We consider the astrophysical relevance of these experiments applying published models of jet deflection developed for AGN and YSOs. Fitting the observed jet deflections to quadratic trajectories predicted by these models allows us to recover a set of plasma parameters consistent with the data. We also present results of 3-D numerical simulations of jet deflection using a new astrophysical Adaptive Mesh Refinement code. These simulations show highly structured shocks occurring within the beam similar to what was observed in the experiments

astro-ph↗

arXiv2001

Laboratory Astrophysics and Collimated Stellar Outflows: The Production of Radiatively Cooled Hypersonic Plasma Jets

We present first results of astrophysically relevant experiments where highly supersonic plasma jets are generated via conically convergent flows. The convergent flows are created by electrodynamic acceleration of plasma in a conical array of fine metallic wires (a modification of the wire array Z-pinch). Stagnation of plasma flow on the axis of symmetry forms a standing conical shock effectively collimating the flow in the axial direction. This scenario is essentially similar to that discussed by Canto\' ~and collaborators as a purely hydrodynamic mechanism for jet formation in astrophysical systems. Experiments using different materials (Al, Fe and W) show that a highly supersonic ($M\sim 20$), well-collimated jet is generated when the radiative cooling rate of the plasma is significant. We discuss scaling issues for the experiments and their potential use for numerical code verification. The experiments also may allow direct exploration of astrophysically relevant issues such as collimation, stability and jet-cloud interactions.

astro-ph↗