Variations in solar luminosity from timescales of minutes to months

We present the power spectrum of solar irradiance during 1985 and 1987, obtained from the active cavity radiometer irradiance monitor project from timescales of minutes to months. At low frequency, the spectra are Lorentzian [proportional to 1/(f₂ + f₀²)]. At higher frequencies, they are proportional to f^-1/2. A linear, stochastic model of the turbulent heat transfer between the granulation layer (modeled as a homogeneous thin layer with a radiative boundary condition) and the rest of the convection zone (modeled as a homogeneous thick layer with thermal and diffusion constants appropriate the lower convection zone) explains the observed spectrum.