  We present a theory for wave scintillation in the situation with a
time-dependent partially coherent source and a time-dependent randomly
heterogeneous medium. Our objective is to understand how the scintillation
index of the measured intensity depends on the source and medium parameters. We
deduce from an asymptotic analysis of the random wave equation a general form
of the scintillation index and we evaluate this in various scaling regimes. The
scintillation index is a fundamental quantity that is used to analyze and
optimize imaging and communication schemes. Our results are useful to quantify
the scintillation index under realistic propagation scenarios and to address
such optimization challenges.
