Hα Observations of Flare-Initiated Disturbances with Velocities ~1000 km/sec.

During 1959 a program of six frame per minute Ha cinematography revealed four events where a flare unambiguously resulted in abrupt activation of one or more absorption filaments, situated in preferred directions, at distances of 150 000 to 700000 km from the flare. The flares have a distinct premaximum intensity "explosive" phase, at which time the luminous borders appear to suddenly expand at rates of several hundred km/sec. It was inferred that the filament activations resulted from a disturbance initiated at the explosive phase and propagated through the solar atmosphere to the filaments. The four cases indicated assignment of a velocity of 1000 km/sec to the disturbance. Since January 1960 observations have been conducted with the 0.5 A birefringent filter bandpass displaced 0.5 A to the blue wing of Ha resulting in greater sensitivity to Doppler-shifted absorption features; four additional such events have been detected. Three flares have been observed where direct measurement of Doppler-shifted features confirm the high velocities inferred from subsequent filament activations. At 2039 UT, June 25, 1960 an importance-2 flare initiated a disturbance which activated and reactivated five separate filaments. Direct measurement resulted in assignment of a minimum velocity of 2500 km/sec to a broad cloudlike feature. The eight flare-initiated disturbances detected to date have transverse velocity components ranging from 550 to 2500 km/sec, suggesting a close relation to flare associated disturbances thought to result in type-Il bursts and geomagnetic storms.