Our experiments consist of several campaigns to understand and quantify how shock fronts behave in the laboratory, and then connect what we see there to analogous situations in astrophysics. Each campaign is summarized below. The links point to the data from each. Publications related to the work are available.
This research is supported by the DOE through the NLUF program.
I. Jets deflected from obstacles (May 2005 - March 2007)
When a jet impacts an obstacle like a molecular cloud at an oblique angle, shocks form within the obstacle and the jet is deflected. Examples of this phenomenon occur in astrophysics. This campaign studied the internal shock waves that formed within a sphere, and the dynamics with the deflected bow shock. The experiments, combined with numerical simulations and new astrophysical observations appeared in Hartigan et al. 2009 ApJ 705, 1073..
II. Shocks overrunning single and dual clumps (August 2007 - March 2009)
This campaign began to investigate the types of shock fronts that are present when the medium into which the shock propagates is highly inhomegeneous. We began this work by producing a blast wave that overran a single sphere, and then graduated to two spheres with various spatial offsets to learn about shadowing and internal reflections.
III. Shocks overrunning multiple clumps (September 2010 - March 2011)
A natural outgrowth of the first set of experiments was to explore what happens when multiple spheres were present. These situations more closely resemble the true astrophysical cases. Data from these experiments helped us to understand images from the Hubble Space telescope, described in Hartigan et al. 2011, ApJ 736, 29. There is a PR video related to this work.
IV. Mach stem experiments (August 2011 - February 2013)
The aim of these experiments is to understand what happens when shock waves intersect one-another. This work was motivated by Hubble Space telescope movies that show a series of overlapping bow shocks that are part of supersonic jets from young stars. The jets are driven out as material from a dense disk of gas and dust accretes onto the star. In order to interpret the astrophysical observations correctly we must understand the geometry of the shocks in the jet. Theoretically one expects a perpendicular (a.k.a. normal) shock called a Mach stem to form under some circumstances. The goal of the experiments was to quantify the conditions under which such Mach stems form, and to determine how easily they are destroyed. All of the numerical, experimental and observational efforts for this project were combined and published in Hartigan et al. 2016, ApJ 823, 148.
V. Magnetic shock experiments (September 2013 - February 2014)
Experiments designed to explore the effect of magnetic fields on fragmentation and fluid dynamical instabilities in strong shock fronts.
VI. Magnetic wire experiments (October 2014 - December 2016)
Experiments designed to model the deflection of plasma by a planetary magnetosphere using a current-carrying wire as an analogue for a magnetized planetary body. Designs were published in Liao et al., 2015, HEDP 17, 38
VII. Accretion Column experiments (May 2015 - October 2015)
Images of an accretion shock caused by a collimated jet of plasma
VIII. Drive Design for Magnetized Flows (October 2015)
Thompson scattering experiments related to fine-tuning densities and flow velocities for magnetic experiments.