Date of Award

Winter 1984

Project Type

Dissertation

Program or Major

Physics

Degree Name

Doctor of Philosophy

Abstract

This thesis covers four topics in the theory of interplanetary cosmic-ray propagation:

The first part involves the time-dependent, spherically-symmetric, solar modulation of galactic cosmic rays. A numerical technique was introduced for the solution of this problem. A model for the solar-cycle variation in cosmic-ray intensity illustrated this method, using enhanced particle scattering regions. This model accounted for at least three key sets of observations: the cosmic-ray radial intensity gradients; the decrease in cosmic-ray intensity over the solar cycle; and the hysteresis between low and high-energy cosmic rays.

The second section contains an attempt to explain recent observations which show that cosmic-ray electrons are returning to higher intensities, characteristic of solar minimum, faster than cosmic-ray protons of about the same energy, the reverse of the previous eleven-year cycle. This section tests a suggested reason for the observations: velocity and rigidity differences between protons and electrons due to their different masses. The time-dependent, spherically-symmetric model of the first section generated the necessary lag in the relative recovery rates, but only as observed in the previous solar cycle.

The third section involves the solar modulation of galactic antiprotons. It appears that a recent low-energy measurement of these particles has given cosmic-ray theorists trouble devising an interstellar spectrum to fit the observations. Using a steady-state, spherically-symmetric, numerical modulation code, a solution that reasonably fits the observed 1980 galactic proton spectrum at 1 AU implied that the modulation used for the data interpretation has been significantly underestimated.

The final section contains a spherically-symmetric, steady-state calculation of the effects of a strong termination shock in the heliosphere. In the end, high-energy particles cooling down in the upstream solar wind overwhelmed any accelerated low-enegy particles, those which would be most affected by the shock. The overall effect of a shock on the near-Earth spectra seems negligible.

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