Some Investigations on Long-Wave Propagation

Abstract

The paper describes some experimental observations on the propagation of long waves (164 kc./s.) from Radio Tashkent (42°N, 69°E.) to Delhi (28°35'N., 77°5'E.) over a distance of 1650 km. The amplitude of the received wave is continuously recorded at Delhi. The recordings show well defined sudden increases in amplitude (and gradual fall) coincident with solar flares. The data from 9th August to 16th December 1958 have been analysed and 144 instances of sudden increase observed during the period. It is found that flares of all classes of importance give rise to sudden increases in amplitude (S I.L.). The times of beginning and maximum of these two events agree fairly well (within 5 to 10 minutes). The variation of Hα line width during a flare is also well correlated, in some instances, with the change in amplitude of the corresponding S.I.L. The height of reflection of this obliquely incident long wave is determined from sunrise effect and is 65 km. The usefulness of S.I.L. as a flare patrol and in the short-term forecasting of S.I.D.s is discussed.