Ionospheric data of Islamabad (33.75șN, 72.87șE) have been used to study the seasonal and annual Es occurrences, using the ionospheric Es parameters foEs, fbEs and total blanketing due to Es over the period 1989 – 97. It is observed that the seasonal % occurrences of Es (foEs), blanketing frequency (fbEs) and total blanketing due to Es are maximum in summer and minimum in winter both for day and night – time throughout the period 1987 – 1997. The % occurrence of the first two parameters is greater at night than during the day in all the seasons, while a reverse trend exits for the third parameter. Therefore, the radio communicators are liable to face problems in HF communication during the season of summer irrespective of the solar epoch, Moreover, they are liable to face more problems during day – time than at night. Best conditions for HF communication prevail in winter. The annual % occurrence of Es (foEs) and blanketing frequency (fbEs) both for day and night – time are observed to be overall in phase with the solar cycle, while that of the total blanketing due to Es overall in anti phase. |
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