Electric Currents as a Probable Cause of Daily Magnetic Variation

[摘要] In 1889 A. Schuster showed that daily magnetic variation could be divided into the magnetic variation coming from an external origin and that of internal origin. S. Chapman has concluded that the latter can be perfectly explained as an electro-magnetic induction of the former into a model earth having the following property: a uniform distribution of electric conductivity throughout a sphere concentric with the earth, but of radius 4 per cent. less than of the earth, the material in the outer 4 per cent. layer, about 250km thick, being non-conductive.The probable cause of the daily, magnetic variation of external origin has been believed to be some electric current flowing at some level above the earth's surface.The features of this current system were investigated by Bartels with great success, but the location of this current system still remained unknown.Recent investigations of the radio fade out showed us that this phenomenon is generally accompanied by the augmentation of the amplitude of the S field and that the radio fade out is due to the sudden increase of the ionization of the lower part of E layer, and possibly also in F1 layer.The present author deduced, with considerable success, new formulae to calculate the electric current and the vertical components of the magnetic force from the horizontal components. The horizontal distribution of the electric current obtained by the author's method coincides very well with that obtained by Bartels as shown in the figures. The vertical components calculated by the author's method explain the observed vertical component in a rate of about 75% and 55% for the external and internal magnetic variation respectively.Thus referring to the values obtained by Chapman of the location of the internal current system, we can evaluate the location of the external current system, with the result that it can be considered, without large error, to be E or F1 layer.Namely the situation of the external current was, first, given in this paper from the observed values of the magnetic forces and this result coincided very well with that estimated on the basis of wireless researches.Thus the result of this paper seems to be a valuable contribution and a strong support to the reconstruction of the theory of daily magnetic variation and also to the physical investigation of the ionosphere itself.

[学科分类] 大气科学