Our understanding of astrophysical collisionless shocks is limited because
they occur in conditions too extreme to model in terrestrial laboratories.The plasma processes responsible for heating and isotropizing the electron
and ion distributions at the shock front are poorly understood. In cases
where the collisionless shock is non-radiative (adiabatic) and propagates
into partially neutralgas, the excitation of cold hydrogen and charge exchange with hot ions
close to the shock frontproduces both narrow and broad lines in the optical (Balmer emission) and
UV (Lyman emission). The excitation of heavy ions (He, C, N and O) alsoproduces broad emission lines in the optical and UV range. I will show how
spectroscopy of non-radiative supernova remnants provides valuable
diagnostics of the plasma heating processes in highMach number interstellar shocks. The observations can be compared with
predictions from numerical shock models to (1) infer the degree of
electron-ion and ion-ion temperatureequilibration in collisionless shocks from the emission line widths and
flux ratios, and (2) gain clues to the collisionless heating
mechanism(s) from the shapes of the broad hydrogen line profiles.
Begin streaming QuickTime of the whole talk (high bandwidth).
Begin streaming RealMedia for the whole talk: high bandwidth or medium bandwidth.
Or, stream audio only for the whole talk: high bandwidth or low bandwidth. (Or, right-click to download the whole audio file.)
To begin viewing slides, click on the first slide below. (Or, view as pdf.)
Author entry (protected)