University of Tehran Press Journal of the Earth and Space Physics 2538-371X 33 2 2007 06 22 - - 18986 FA Journal Article Variations in the intensity of solar radiation and solar zenith angle related to the earth's surface during the daytime, night-time and also during a year cause some variations in ionospheric electron densities. In this study, the effect of solar radiation on the ionospheric F2 layer in one day is studied and the direct relation of ion production with solar variation is proved. Besides, ionospheric variations during a year, that are due to thermospheric circulation and atmospheric composition changes, are studied. Moreover, the relation between the 11 year sunspot cycle and long period variation in the ionosphere is proved. Variations in the intensity of solar radiation and solar zenith angle related to the earth's surface during the daytime, night-time and also during a year cause some variations in ionospheric electron densities. In this study, the effect of solar radiation on the ionospheric F2 layer in one day is studied and the direct relation of ion production with solar variation is proved. Besides, ionospheric variations during a year, that are due to thermospheric circulation and atmospheric composition changes, are studied. Moreover, the relation between the 11 year sunspot cycle and long period variation in the ionosphere is proved. https://jesphys.ut.ac.ir/article_18986_b5c480f68b9454070586dd8151546e16.pdf