The author observed the micropulsation of the terrestrial magnetism by the specially designed induction magnetometer at Onagawa, near Sendai, and studied the statistical investigation of the micropulsation which occured at the time of the magnetic disturbance.
Main results are as follows:
1) Micropulsations are accompanied by the magnetic disturbance, specially, the large amplitude of micropulsations occure at the time of the magnetic storm.
2) The sinusoidal regular micropulsations occur much more frequently in the daytime. The author considered that it occurred when the corpuscles coming from the sun penetrated into the ionosphere.
3) Though the sudden commencement occurs simultaneously over the whole area of the earth, the amplitude of the oscillation of
dH/
dt in the hemisphere at daytime is greater than that in the hemisphere at night. This character is very remarkable and occurs almost without exception. Also a remarkable micropulsation of
dH/
dt at the sudden commencement; frequently took places during the summer and equinox.
4) The author observed the variation of the magnetic micropulsation during the solar eclipse on May 9th, 1943, at wakkanai, Hokkaido and Onagawa, near Sendai, and found that the time variation on the terrestrial magnetic field at the time of solar eclipse is the effect of the neutral corpuscular eclipse, and the velocity of the corpuscle is supposed to be 34, 000Km/sec.
5) The current system of the magnetic disturbance accompnied by the irregular micropulsation at the time of the magnetic storm is the same as that of the “Positive Bay Disturbance”. The irregular micropulsation is very remarkable at the perid of the mainpllase of the magnetic storm, and its current system is situated in the auroral zone.
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