A.Khireddine and K. Benmahammed.

The solar radiation system arriving at the surface of the ground that is not emitted by the sun, because of the various phenomena of absorption, diffusion and filtering on the level of the various atmospheric layers, which returns the storage of difficult solar energy, for it fluctuates enormously in the course of time. Thus, the solar radiation varies at the same time periodically and by chance during the year the periodic variations are done at the rate/rhythm seasons which are due to the variations of the variation, while the random fluctuations are especially caused by the disorders atmospheric. In the majority of the weather stations, measurements of the insolation (or sunning) are done permanently whereas those of the solar irradiation are rather rare. However various approaches make it possible to correctly consider the flow of irradiation solar starting from the data of insolation at knowing the equation of angstrom. There are also methods which make it possible to describe or reproduce the time and daily variations of the insolation or the solar irradiation, it is those which are based on the use of autoregressive process.