"Generation of Collisionless Shocks by a Laser-Driven Magnetic Piston," by Derek Schaeffer (UCLA)

Date: 
Thursday, October 23, 2014 - 1:00pm to 2:00pm
Series: 
Plasma Seminars

Plasma Seminar

Physics and Astronomy Building (PAB) Room 4-330
Thursday, October 23, 2014
1-2pm
Refreshments at 12:30pm

Speaker: Derek Schaeffer (UCLA)

Talk Title: "Generation of Collisionless Shocks by a Laser-Driven Magnetic Piston"

Abstract:

Collisionless shocks, in which dissipation is provided by electromagnetic rather than collisional effects, are ubiquitous in many space and astrophysical plasmas.  However, since these shocks are largely steady-state, in situ measurements by spacecraft have focused on properties of pre-formed shocks.  Recent experiments at UCLA have successfully generated magnetized collisionless shocks, allowing new studies of shock formation relevant to space shocks.  These experiments combined a preformed, magnetized background plasma from the Large Plasma Device with a magnetic piston driven by the high-energy Raptor laser incident on a carbon target.  Magnetic flux measurements and 2D hybrid simulations indicate that a magnetosonic pulse consistent with a low-Mach number, quasi-perpendicular collisionless shock was formed in the ambient plasma.  The characteristics of the shock are compared to previous experiments in which no shock formed, and the results suggest that the various experimental conditions can be organized into distinct regimes by coupling strength.  With additional experiments on the early-time parameters of the laser plasma utilizing Thomson scattering, spectroscopy, and fast-gate filtered imaging, these regimes are found to be in good agreement with theoretical shock formation criteria.