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.

Ionospheric absorption of cosmic radio noise

“…For a discussion of the problems of identifying separate events the reader is referred to BASLER and OWREN (1964). Those authors took most of their information from the following sources: OBAYASHI and HAKURA (1960a, b), SINNO (1961), , KAHLE (1962), NOYES (1962), GREGORY (1963), JENKINS and PAGmS (1963), MALITSON (1963), andWARWICK andHAURWITZ (1963). A list of 48 "principal" PCA events in the period 1962-1963 can be found in the review by BAILEY (1964).…”

“…As mentioned in (I), SINNO (1961) and HAKURA (1961) have distinguished between slow and fast onset events. The fast class encompasses, according to Hakura, those events with time delays of less than five hours between the flare and the beginning of the PCA.…”

A Study of the Reliability of Polar Cap Absorption as a Predictor of Geomagnetic Storms

“…The type IV radio noise bursts which often accompany large flares are 80 percent correlated with polar-cap blackouts, according to Sinno (1962), who has tabulated the pre-SSC polar-cap blackouts for the period 1956 to 1960 and the associated solar and geophysical data. He has also discussed the cause of the phenomenon, and given references to the earlier literature.…”