Abstract
HF Doppler data over two long low latitude radio paths (ATA-Haringhata and JJY-Haringhata) for the period June, 1966 to December 1972 has been examined for effects of sudden commencements. It is noticed that for the same type of sudden commencement, i. e., SC (+), four distinct types of ferequency deviations exist, designated as SCFD (+), SCFD (-), SCFD (+-) and SCFD (-+). The occurrence and the nature of the frequency deviation effect due to sudden commencement is independant of the amplitude of the sudden commencement. A positive correlation between the amplitude of the maximum positive frequency deviation and maximum negative frequency deviation is noticed in composite events: SCFD (+-) and SCFD (-+).
