On the High Eruptive Solar Prominence of April 28, 1938
Koiwai, M.
Abstract
A remarkable eruptive prominence was visible on the east limb of the sun, about 30°south of the equator, on the morning of April 26, 1938.
The prominence ascended very quickly and reached a height about 330 thousand km at about 9h 35m (J.S.T.) and then an end of the prominence considerably curved toward the equator. A part of the prominence seemed to continue its ascending feature, and the other part began to descend.
Between 8h 35m and 9h 45m, 28 measurements were made every few minutes with the Zeiss 20cm equatorial, using the Ha line.
The mean ascending velocity of the prominence derived from the first 40 minutes, was 130 km/sec. At first the prominence rose slowly about 23km/sec. to a height 40,000 km, and then indicated a sudden acceleration increasing the velocity 850 km/sec. up to a height of 140,000 km. A final change gave a velocity of 120 km/sec. up to a height of 30,000 km.
For about fifteen minutes from 8h 45m corresponding to occur the great outburst, the moving gases presented a great negative radial velocity and at the same time attained its greatest brilliancy. Considering the tremendous velocity, the great brightness and the coincidence of the time, this spectacular eruption might be associated with the ratio fade-out occurring at 8h 45m.
It is known that radio transmission fade-outs to which was first called attention by Dr. T. H. Dellinger, are closely connected with bright hydrogen eruptions particularly located at central portions of the sun.
To make sure that any particular eruption might occur on the surface of the sun, the author asked to the astronomers at Tokyo Astronomical Observatory to examine their spectroheliograms for that dates in question and he was informed that there had been no unusual activity on the sun.
Therefore it is probable that the remarkable emptive prominence was closely connected with the radio fade-out.
Finally, the author treated the relation between the prominence and flocculi which appeared on the successive dates.
