A comparison of g((1)) (tau), g((3/2))(tau), and g((2))(tau) for radiation from harmonic oscillators in Brownian motion with a coherent background

We compare the field-fieldg((1))(tau), intensity-fieldg((3/2))(tau), and intensity-intensityg((2))(tau) correlation functions for models that are of relevance in astrophysics. We obtain expressions for the general case of a chaotic radiation, where the amplitude is Rician based on a model with an ensemble of harmonic oscillators in Brownian motion. We obtain the signal to noise ratios for two methods of measurement. The intensity-field correlation function signal to noise ratio scales with the first power of vertical bar g((1))(tau). This is in contrast with the well-established result of g((2))(t)((2))(tau) which goes as the square of vertical bar g((1))(tau)vertical bar.