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Variations of Focus Latitude and Intensity of Equivalent Current System of Geomagnetic Solar Daily Variation with a Period from about Ten to Thirty Days
An analysis of day-to-day change of geomagnetic solar daily variation in the west Pacific region was carried out.
First, using hourly mean value data of the horizontal intensity and the west declination at four stations from December in 1970 to February in 1972, focus latitude and measure of intensity were estimated day by day except extremely geomagnetically disturbed days. Day-to-day changes of focus latitude and measure of intensity show a variation with a period from about ten to thirty days as well as a variation with a period of few days. These variations are not due to geomagnetic disturbances.
Next, using the method of power spectral analysis, eminent peaks and their time variation was investigated. Peaks of the power spectral density of change of focus latitude are found at periods of about 33 days, 17 days, 10 days and 7 days. And those of measure of intensity are found at periods of about 25 days and 14 days. Each and al1 of these peaks are not always seen during the whole period of the analysis, but the eminent peaks are different for different partial periods of the whole.
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