SHOCK INSTABILITIES

It is well known that adiabatic shocks in ordinary gases are stable to both tranverse and longitudinal perturbations, but this need not be t rue if there are significant thermal effects due to chemical reactions or cooling processes. For example, detonation waves in gases are obse rved to form cellular structures if the chemical reaction is sufficien tly temperature sensitive and a similar instability occurs in radiativ e shocks in the ISM if their speed exceeds 150 km s(-1). This means th at interstellar shocks will be subject to this radiative instability i n many cases. The temperature sensitivity of the nuclear reactions in Type I supernovae is also such that we would expect detonation waves i n these objects to have a cellular structure.