Measurements of galactic hydrogen and helium isotopes from 1978 through 1983

The differential flux of the hydrogen and helium isotopes was measured using an instrument on the ISEE-3 spacecraft during solar quiet time periods from August 1978 through December 1983. These measurements cover the energy range from 26 MeV/nucleon through 138 MeV/nucleon for both H-1 and He-4, from 24 to 89 MeV/nucleon for H-2, and from 43 to 146 solar activity varied from near minimum to maximum conditions causing the observed flux of galactic cosmic rays to modulate by an order of magnitude. To describe the propagation in the galaxy, it was found that the standard leaky box approximation with an escape path length of 6.7 g/sq cms forms a self consistent model for the light cosmic ray nuclei at the observed energies.