Accretion shocks in the laboratory: Design of an experiment to study star formation

Abstract

We present the design of a laboratory-astrophysics experiment to study magnetospheric accretion relevant to young, pre-main-sequence stars. Spectra of young stars show evidence of hotspots created when streams of accreting material impact the surface of the star and create shocks. The structures that form during this process are poorly understood, as the surfaces of young stars cannot be spatially resolved. Our experiment would create a scaled “accretion shock” at a major (several kJ) laser facility. The experiment drives a plasma jet (the “accretion stream”) into a solid block (the “stellar surface”), in the presence of a parallel magnetic field analogous to the star’s local field. We show that this experiment is well-scaled when the incoming jet has ρ∼10−6−10−5gcm−3 and u∼100−200kms−1 in an imposed field of B ∼ 10 T. Such an experiment would represent an average accretion stream onto a pre-main sequence star with B ∼ 700 G.