# Accession Number:

## AD0614100

# Title:

## AN INTERPLANETARY DIFFUSION MODEL FOR THE TIME BEHAVIOR OF INTENSITY IN A SOLAR COSMIC RAY EVENT,

# Descriptive Note:

# Corporate Author:

## IOWA STATE UNIV IOWA CITY

# Personal Author(s):

# Report Date:

## 1965-04-01

# Pagination or Media Count:

## 63.0

# Abstract:

It is found possible to give a coherent interpretation of the time history of the intensity of several solar cosmic ray events in terms of a unified interplanetary diffusion model which assumes that the diffusion coeffieient D M r to the B power, where r is the heliocentric radial distance and M and B are parameters, which may be dependent on particle energy E. The model is particularly successful in accounting for the decay phases. For the September 28, 1961 event M varies as E to the 0.33 power and, assuming spherical geometry, B is equal to one for 55 E 500 MeV and decreases rapidly at lower energies. At r 1 A.U. the mean free path lambda is about 0.081 A.U. for E 200 MeV and 0.15 for E 23 MeV. The energy dependences of B and lambda suggest 0.006 A.U. as the order of magnitude of the scale size of irregularities in the interplanetary magnetic field. The source spectrum is inferred. The possibility of non-spherical geometry of diffusion is considered, as is the implication of the results with respect to the solar modulation of galactic cosmic radiation. Author