Seasonal Variations of Focus Latitude and Intensity of Sq Current System
Shiraki, M.
Abstract
Investigations on seasonal variations of focus latitude φ1 and a measure of intensity lΔγ１/Δφl of Sq current system are carried out using data of horizontal intensity in the west Pacific (1958-1969), the north American (1948-1962) and the Australasian (1949-1958) regions. The data are divided into two or three groups according to the yearly mean sunspot numbers, and φ1 and lΔγ１/Δφl are determined month by month for each group in each region. They show remarkable seasonal variations through a year and the following characteristics are found.
(1) Seasonal variations of φｆ show different aspects among groups of sunspot numbers, and these differences are due to changes of φｆin local winter in both hemispheres. φｆ in winter shifts polewards, according to the decrease of sunspot numbers.
(2) A difference ofφf is seen between the vernal and the autumnal equinoxes. φｆ in autumn is located in lower latitude relatively as compared with φｆ in spring in both hemispheres, and this phenomenon is not related to the sunspot numbers.
(3) Regional, dissimilarity of seasonal variation is very large between the west Pacific and the north American regions. The aspect in the Australasian region is rather similar to that in the west Pacific region.
(4) The aspects of seasonal variations of lΔγ１/Δφl are different among three regions. They are dissimilar to seasonal variations of daily range of declination in each region.
