GEOMAGNETIC Sq-VARIATION DURING NIGHT-TIME By

Concerning the geomagnetic Sq-variation, many papers have discussed varia-tions during day-time. In fact, that is the main part of Sq-variation, but, on a close investigation, Sq-variation during night-time shows a systematic morphology. In this paper, using the data of the Second Polar Year, some special methods of statistical investigation on Sq are shown, and a distinct seasonal difference is detected. In the course of study, Non-Cyclic-Change and non-systematic errors are discussed from the stand-point of statistical investigation of geomagnetic variations. The research is not finished and investigations of the asymetric part centered at mid-night must be undertaken. This result of data-arrangement will serve to discuss the base-value of the geomagnetic field at the respective ob-servatories, and also to supply original data for theoretical investigations such as the wind-system in the ionosphere and the conductivity-anomaly of the earth's interior. 1