Recurrent geomagnetic
storms, produced by coronal holes, overcome the effect of
solar irradiance on the
ionosphere during declining and minimum phases of
solar activity.
Section 1 contains five subsections with results on 27 - day response of low - latitude
ionosphere to
solar extreme - ultraviolet (EUV) radiation, response to the recurrent geomagnetic
storms, long - term trends in the upper atmosphere, latitudinal dependence of total electron content on EUV changes, and statistical analysis of ionospheric behavior
during prolonged period of
solar activity.