  Laser-ablated high-energy-density (HED) plasmas offer a promising route to
study astrophysically relevant processes underlying collisionless shock
formation, magnetic field amplification, and particle acceleration in the
laboratory. Using large-scale, multi-dimensional particle-in-cell simulations,
we explore the interpenetration of laser-ablated counter-streaming plasmas for
realistic experimental flow profiles. We find that the shock formation and its
structure are substantially different from those of more idealized and commonly
considered uniform flows: shock formation can be up to 10 times faster due to
the transition from small-angle scattering to magnetic reflection and the shock
front develops strong corrugations at the ion gyroradius scale. These findings
have important consequences for current experimental programs and open exciting
prospects for studying the microphysics of turbulent collisionless shocks with
currently available high-energy laser systems.
