Observation of Collisionless Electrostatic Shocks

Abstract

Large-amplitude ion-acoustic waves ($\frac{e\ensuremath{\phi}}{k{T}_{e}}\ensuremath{\lesssim}0.3$) are excited in the University of California, Los Angeles double-plasma device by the interpenetration of two plasmas with high electron-to-ion temperature ratios ($6<\frac{{T}_{e}}{{T}_{i}}<20$). A compressional wave with a ramp shape is found to steepen in a fashion consistent with the classical overtaking predicted by the usual Riemann invariants. This steepening continues until dispersive short scale ($k\ensuremath{\approx}\frac{1}{2}{k}_{\mathrm{D}}$) oscillations develop at the front. Ions streaming in front of the shock are also observed.