2008 APS April Meeting and HEDP/HEDLA Meeting
Volume 53, Number 5
Friday–Tuesday, April 11–15, 2008;
St. Louis, Missouri
Session 6HE: Shocks in Stellar Jets
10:50 AM–12:30 PM,
Saturday, April 12, 2008
Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel),
Room: Promenade F
Sponsoring
Units:
HEDP HEDLA
Chair: Sergey Lebedev, Imperial College
Abstract ID: BAPS.2008.APR.6HE.3
Abstract: 6HE.00003 : Experiments with supersonic plasma jets at Omega
11:40 AM–12:05 PM
Preview Abstract
Abstract
Author:
John M. Foster
(AWE Aldermaston)
Large-scale directional outflows of supersonic plasma, also known as jets,
are often encountered in astrophysics. These jets propagate through the
interstellar medium which is often clumpy and where inhomogeneities affect
the morphology of the shocks that are generated. The hydrodynamics is
difficult to model as the problem is inherently 3D, and the clumps are
subject to a variety of fluid instabilities as they are accelerated and
destroyed by shocks. Very large scale inhomogeneities may result in
deflection of the jet itself. The traditional approach to understanding such
phenomena is through theoretical analysis and numerical simulations.
However, such numerical simulations have limited resolution, often assume
axial symmetry, do not include all relevant physical processes, and may fail
to scale correctly in Reynolds number and other key dimensionless
parameters. They are frequently not tested by comparison with laboratory
experiments.
In recent years, we have carried out experiments at the University of
Rochester's Omega laser, to investigate the physics associated with the
propagation of plasma jets and shocks through both homogeneous and
inhomogeneous media. These experiments have close analogues with structures
observed in jets from young stars. Jets and shocks are created in
experimental assemblies that are ablatively driven by a 190-eV temperature
`hohlraum' (which is itself heated by the Omega laser), and subsequently
propagate into a low density hydrocarbon-foam medium. The foam is either of
uniformly low density, or contains localised (higher density) perturbations.
Interaction of jets with this fluid results in the development of a bow
shock, and, in the case of a single density perturbation, results in
deflection of the jet (a laboratory analogue of the astrophysical object
HH110). In the case of a shock propagating through an inhomogeneous medium
(foam containing one or more sapphire spheres), the resulting complex shock
interactions are analogous to the flow of clumpy interstellar matter through
the working surfaces of HH objects. The hydrodynamic structures that develop
in these experiments are revealed by x-ray `backlighting' radiography. These
complex experimental data challenge both astrophysical and laser-plasma
hydrodynamics computer codes. We discuss 2D and 3D simulations of these
experiments, and their potential scaling to astrophysical systems.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2008.APR.6HE.3