Characteristics of Solar Energetic Particles which Excite Polar-Cap Blackouts

Abstract

Ejection and prapagation of the particles which excite abnormal ionization in the polar upper atmosphere are investigated from some statistical considerations on ionospheric data f-min and cosmic radio observation by riometer.
Relations between the flares and the polar-cap blackouts insist the trapping of particles into the cloud which would be responsible for the geomagnetic disturbances; that is, a part of the energetic particles ejecting from the flare propagate with relativistic velocity in interplanetary space along the twisted solar magnetic line of force extending to the earth and excite the S-type polarcap blackouts having sudden onset within a few hours after flare; on the other hand, another part of the energetic particles ejecting from the flare is trapped into the cloud and is carried with rather low velocity, then the particles would reach the earth by leaking from the cloud and excite the G-type polar-cap blackouts having gradual onset about 10 hours before commencement of geomagnetic storms.