Cosmic-Ray Observations at Very High Altitudes During Periods of Intense Solar Activity

The records of a number of balloon flights which coincided with outstanding solar disturbances during the period 1947-1952 have been subjected to detailed statistical analysis in a search for associated fluctuations in the primary cosmic-ray flux. The intensity at very high altitudes was enhanced in four cases, and normal on five occasions when rf radio disturbances and/or visually-observed solar flares occurred. In some instances, outstanding chromospheric eruptions are not accompanied by any detectable increase in the flux of primary cosmic-ray particles even down to the very low energy required for just penetrating 10 g/${\mathrm{cm}}^2$ of matter. On the other hand, additional low-energy particles apparently associated with solar disturbances sometimes are detected at very high altitudes, even when the flares are small and the observing station is outside the morning impact zone.