Energy Spectra of Anomalous Cosmic-Ray Oxygen During 1977-1987

Abstract

We have previously reported that the energy of the peak intensity of the spectrum of anomalous cosmic-ray oxygen moved upwards by a factor of -2 near the time of the reversal of the solar magnetic field in 1980. An energy shift which persists into the next solar minimum period would agree with a key prediction of a theory of the acceleration and propagation of the anomalous component by Jokipii. That model also predicts distinctly different spectral shapes in the two halves of the solar magnetic cycle. Although we cannot yet rule out the possibility of a long-term hysteresis in the recovery of the low-rigidity particles, our spectral measurements through late 1986 agree remarkably well with these predictions.