ANALYTICAL THEORY OF FLUCTUATIONS IN THE INTEGRATED SOLAR FLUX IN THEEDDINGTON APPROXIMATION

Fluctuations in the integrated solar flux in a stratified atmosphere a re investigated. By solving the equations of radiation hydrodynamics a nalytically and justifying the boundary conditions, we develop a model of nonadiabatic oscillations that takes into account the interaction of thermal and acoustic waves and their transformation. The model prov ides the first explanation of the observed peak in the distribution of the fluctuations of the integrated solar flux at 3.3 mHz (oscillation s with a period of 5 min). At this frequency, the relative amplitude o f the flux fluctuations is similar to 10(-5), in agreement with spaceb orne observations. The contributions of thermal and acoustic oscillati ons to the integrated flux and the velocity of motion are determined. It is established that the oscillations observed in the integrated sol ar flux are thermal, while the oscillations in the the velocity of mot ion are acoustic p-modes. A theoretical spectrum of the phase shift be tween the brightness and velocity oscillations (I-V spectrum) is calcu lated; this phase shift is in agreement with the phase shift between t he thermal waves and acoustic waves at the same frequency.