Parviz Ghavamian,  Rutgers University 

Title: Using Optical Spectra of Young Supernova Remnants to Study the
            Physics of Collisionless Shocks
 
Abstract: Our understanding of collisionless shocks is particularly poor 
because they occur in conditions too extreme to model in terrestrial 
laboratories.  When a collisionless shock propagates through a partially 
ionized medium, the excitation of cold Hydrogen and charge exchange with 
hot ions produces both narrow and broad Balmer emission lines.  I will 
describe spectroscopic observations of 'Balmer-dominated' shocks in the 
Cygnus Loop, RCW 86, Tycho, SN 1006 and DEM L 71 supernova remnants.  
I will also describe how numerical shock models can be combined with 
the observational data to infer the degree of electron-ion temperature 
equilibration and ionization structure of supernova blast waves.   
Balmer-dominated shock spectra are powerful tools for interpreting 
X-ray observations of young SNRs and examining their expansion kinematics.