THE SIMULATED FEATURES OF HELIOSPHERIC COSMIC-RAY MODULATION WITH A TIME-DEPENDENT DRIFT MODEL .2. ON THE ENERGY-DEPENDENCE OF THE ONSET OF NEW MODULATION IN 1987

A time-dependent axially symmetric drift model with an emulated wavy heliospheric neutral sheet (HNS) is used to simulate time-dependent modulation for the period 1985-1989. In the first of this series of papers we showed very realistic intensity-time profiles for 1 GeV protons for this period. We illustrated that the observed time delays in the time of minimum modulation with increasing radial distances in 1987 could be simulated with our model. Radial and latitudinal gradients for these protons were found markedly compatible with observations. For this paper the same model is used to extend our calculations to other energies in order to study a possible energy-dependence of the onset of new modulation at various radial distances in 1987. It is found that the model, with the outward propagating changes of the HNS as the only time-dependent parameter, predicts essentially no energy-dependence in the time when new modulation started in the simulated 1987. However, when a more practical approach in defining " constant " modulation in 1987 is followed, our calculations can be interpreted to indicate that the end of the recovery period in 1987 happened progressively earlier and the onset of new modulation progressively later the higher the rigidity of the cosmic rays. This period of relatively unchanged modulation is predicted to last longer with increasing radial distance.