GEOMAGNETIC VARIATIONS IN THE VICINITY OF TOTTORI, FACING THE JAPAN SEA, IN THE SOUTH-WESTERN JAPAN

Abstract

Observations of three components of geomagnetic variations were recently carried out by means of two flux-gate magnetometers in coastal areas of the Japan Sea in the South-western Japan. △Z in short-period geomagnetic variations is negative or upward when J H points to the north, while 」Z is positive or downward at observatories along the Pacific coast of the Central Japan. △Z/△H ratio follows to the period-dependency, amounting to -0.6 or more in short period at stations near the coast, and also to the dependency on the distance from the coast. Parkinson vectors at every station tend to point to the direction almost perpendicular to the coast line. In order to explain these facts, the influence of the undulation of conducting layer beneath the Japan islands and that of electric currents flowing in the Japan Sea (so-called the "coastal effect") are examined and discussed in the present article. Considering the period-dependency of △Z/△H, it may be concluded that the influence of currents in the sea is rather more important than that of the undulation of conducting layer as far as the coastal areas of the Japan Sea in the South-western Japan is concerned.