The article formulates the analytic expression approximating the sequence of Gregorian 11-year solar cycles and the expression of solar activity within one cycle. The dependences of effective thermodynamic temperature of the Sun photosphere and the solar constant, and the solar illuminance constant at the upper border of Earth atmosphere on the year number within one solar cycle were obtained. The generalised analytic expression for integral transmittance of atmosphere (within its spectral window) on the Earth surface for the direct and diffuse components of solar radiation and their sums at different solar altitude angles is presented. The analytic expressions of dependences of irradiance and illuminance on the Earth surface within spectral window of atmosphere and within the visible region of solar radiation spectrum on the year number within a certain solar cycle at different solar altitude angles are obtained. The results of calculation of direct and diffuse components of irradiance and illuminance and their sums in the case of clear sky are presented for example. The proposed approach allows similar calculations to conduct for different types of sky cover. 1. Stanislav Darula “Review of the Current State and Future Development in Standardizing Natural Lighting in Interiors”// Light & Engineering Journal, 2018, Vol. 26, #4, pp. 5–26.
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• 11-year solar cycle
• solar constant
• solar illuminance constant
• solar altitude angle
• cyclic changes
• direct and diffuse components of irradiance and illuminance
• Earth surface