Recovery of Cosmic-Ray Intensities after the “Forbush-Type Decrease”

Abstract

By use of Chree's superposed-epoch method, an investigation was made of the recoveries of cosmic-ray intensities, horizontal components of geomagnetic field and sunspot areas following remarkable Forbush-type decrease. Cosmic-ray intsnsities and horizontal components of the geomagnetic field show recovery curves which resemble each other, but the curve of sunspot areas remains as a lower level than those of the former two. Cosmic-ray intensities show an exponential recovery until the 26th day, with 14.7 days mean life. On the other hand, sunspot areas show such reoovery until only the llth day, with 7.3 days mean life. Can the recovery-curve of logarithms of cosmicray intensity decrements, there exists a knee at the 4th . day. It is proposed that this knee corresponds to the escape of the earth from the corpuscular stream ejected from the sun. (auth) With reference to solsr magnetic observstions, it is proposed that the sun has a magnetic field of dipole character such that the intensity is about one gauss in the polar latitude regions and its polarity is inverse of the earth's. If this field results from a magnetic dipole that the sun may have, the value of this dipole moment is estimated as about 5 xmore » l0/sup 22/ gauss/cm/sup 3/. On the assumption that the magnetic field from this dipole spreads to the outer space surrounding the sun, the orbits of solar cosmic particles were calculated. lt is concluded that a solar dipole magnetic field does not exist between the sun and the earth since the existence of this field can not explain cosmic-ray increases associated with large solar flares. Therefore, although the magnetic field extending from the polar regions into outer space is regarded as closing each other in this spate, the features of this field may be remarkably different from the dipole character. A probable configuration in the interplanetary space of the solar general magnetic field is introduced and discussed. (auth)« less