Bay Disturbances Research Articles

Development and Decay Processes of the Bay Disturbances in Geomagnetic Field

In this study, the progressive change in the current system for the bay disturbance was chiefly examined in four examples with the aid of the world-wide magnetogram copies. The average current system corresponding to the maximum stage of the bay disturbance, which is given in Fig. 3, can be approximated as a result of the dynamo-theoretical calculation under the assumption on the distribution of the electric conductivity in the upper atmosphere such as that the ratio of the conductivity in the auroral zones to that i n the equatorial region is about 14 in the dark hemisphere and about 4 in the sunlit hemisphere. The development and decay processes of individual bay disturbances are not a simple intensification and diminution of the mean current system such as given in Fig. 3, It was noticed that the westward auroral zone current in the dark hemisphere seems to become most intense nearly at the same time when the disturbance force at most part of lower latitude regions reaches its maximum magnitude, and the eastward auroral zone current in the sunlit hemisphere does not yet fully develope by that time and becomes most intense a few tens minutes later.

Current System for SD-Field and the Bay Disturbance

The dynamo-theory for Sq has been proved to be applicable also for SD or the bay disturbance in the geomagnetic field. The disturbance field of SD or bay is generally larger in the dark hemisphere compared with that in the sunlit hemisphere. This fact can be interpreted as a result of the condition that the electric conductivity of the auroral zones is markedly large, especially in the dark hemisphere. In this paper, the current system derived from the dynamo-theory with such conditions is numerically computed for various probable cases with the aid of the perturbation method. The calculated current system, such as given in Fig. 5, is in fairly good agreement with the observed one.

On the Character of the Micropulsation in the Magnetic Storm

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.