抄録
By using data of the ground-level-enhancement (GLE), of solar cosmic rays observed with the neutron and muon monitors in the period 1942-1990, it is shown that the solar proton eruptions producible GLE are forbidden during the transition phase of the heliomagnetic polarity reversal, near the period of the maximum solar activity. It is suggested that the quiescence of GLE is not due to the suppression effect of the proton eruption from the Sun by the strong solar magnetic field, but is due to the deterioration of the proton acceleration efficiency by the structual change of the field during the transition period.
