Eastern Longitude Research Articles

Solar longitude dependence of some characteristics of type III radio bursts from metric to hectometric wavelengths

Using the observed data for metric and hectometric type III radio bursts, the dependence of burst characteristics on the solar longitude has been examined over a wide frequency range. It is found that there exists an east-west asymmetry for the extension of metric type III bursts into hectometric wavelength range. In particular, hectometric bursts are rarely observed for solar flares associated with metric bursts eastward solar longitude 60°E. Furthermore, for eastern longitudes, the low frequency radio observations show a large dispersion in drift time interval.

Sidereal component of the diurnal variation of cosmic-ray intensity

Sidereal variation is studied for cosmic-ray intensity recorded during the last decade. The neutron monitors show a (6÷12) h sidereal component (roughly towards the Milky Way direction of 07 h) not only in 1954 as shown by Conforto and Simpson but throughout 1952–55 with a monthly average amplitude of about 0.05% in contrast to about 0.10% in 1954. A spectrum with negative exponent is indicated. In the peak solar activity period 1956–59, this direction was considerably disturbed and most of the sidereal vectors lay in the other three quadrants. Whereas no discernable latitude or altitude effect was observed, a striking longitude effect was noticed, European longitudes confining to (12÷18) h and Far Eastern longitudes to (18÷24) h. In 1960–64, most of the sidereal vectors lay in the (0÷6) h and (6÷12) h quadrants indicating revival of the 1954 conditions, but only partially. The 1964 minimum did not seem to be as deep as the 1954 minimum. The solar diurnal vector almost disappeared in 1954 but not in 1964. Hence, the problem raised by Dorman about the 22 year cycle in the phase of diurnal variation remains unresolved. A disconcerting feature about neutron monitor data was the inconsistency between the results of some nearby stations. A similar study of the temperature-corrected meson intensities revealed oppositely oriented sidereal vectors from the Northern and Southern hemispheres. It seems, therefore, that there are multiple sources of sidereal variation, some oriented towards the centre of the galaxy, some along the spiral arms and perhaps some others in other directions.