Abstract
The results of a series of 6 Skyhook balloon flights with combination C̆erenkov-scintillation detectors, similar to ones previously described, are used to study spectral cutoffs as a function of latitude and to observe some aspects of temporal variations at high altitude of the alpha particles of the primary cosmic radiation. Observed cutoff energies are found to be in strong disagreement with geomagnetic theory. In one large cosmic-ray decrease the very low-energy portion of the cosmic-ray energy spectrum (300-600 Mev/nucleon) does not seem to be strongly affected.