Ionospheric data of Islamabad (33.75ºN, 72.87ºE) have been used to study the correlation between annual means of foEs and that
of the Smoothed Sunspot Numbers (SSN) during the day and night-time over the solar cycle (1986-97). Also, the variations of seasonal means of foEs over this solar cycle have been studied. It is observed that the variations of annual means of foEs and SSN during the day-time are positively correlated over the period 1987-94, while they are overall negatively correlated at and near the solar minima (1986 & 1996). Moreover, the variations of annual means of foEs and SSN at night are also positively correlated over the period 1987-93, whereas negatively correlated at and near the solar minima (1986 & 1996). The comparison of the three seasons has shown that the maximum of seasonal means of foEs occurs in summer and the minimum in winter, both for day and night-time during the complete solar cycle. |
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