Solar and lunar magnetic tides at midnight

Abstract

The method of Winch (1981) is used to extract the annual and semi-annual components in the magnetic elements starting with hourly values. A series of coefficients of the form: [see full text for equation] are obtained for n = 1 to 4 and k = -2 to +2. Here t is the local time and h is the longitude of the mean sun (giving variation with season). These 20 coefficients can then be used to reconstitute the daily variation curve for any season h. This study investigates the variation ofthe midnight (t = 0) values with season.