A solar explosion, equal in violence to 100 million hydrogen bombs exploding simultaneously, was recorded on film by University observers, Donald H. Menzel, Director of the Harvard College Observatory, told the American Astronomical Society Saturday.

The flare, recorded last month, set a record for all such occurrences observed. The movies were taken with a coronograph, a special telescopic instrument, at the Air Force's Sacramento Observatory in New Mexico.

A bubble of gas expanding at 60 miles per second on the eastern edge of the sun opened the film. It grew steadily more brilliant for five to ten minutes. Suddenly part of the top broke off and sped upward at 700 miles per second or 2 1/2 million miles an hour.

The fragment, about 20,000 miles in diameter, shot out 200,000 miles before becoming too faint to see. The force necessary to produce this sudden acceleration was more than 1,000 times the pull of the earth's gravity, Menzel said.

A billion tons of gas, mainly hydrogen, was expelled. The radiated ultraviolet light energy disrupted radio transmission for a time by affecting the ionosphere, which usually bounces the radio waves back to the earth. The cause of the flares is not fully known, Menzel said. They could be caused by shock waves from tremendous upsurges of gas in the sun's atmosphere or because of electrical and magnetic forces near an active sunspot group.