Articles written in Proceedings – Section A
Volume 61 Issue 4 April 1965 pp 237-254
The effect of solar wind on the relative abundances of galactic cosmic rays is assessed using the theories proposed by Parker1 and Dorman.2 The modulation factors for the ratios of electrons, deuterons, tritons and helium nuclei to protons, helium-3 to helium-4 and light (Z=3–5) to medium nuclei (Z=6–9) are presented.
The effect of the modulation on the differential energy spectra is studied. The form of the spectra, the position of the maximum in the spectra and the relative reduction over a solar cycle place a restriction on the parameters in the solar wind theory. Starting with plausible galactic spectra and by varying the parameters it is possible to fit the form of the solar minimum spectrum but it does not seem possible to produce the relative reduction between minimum and maximum throughout the energy range, with in the framework of the present solar wind theory.
Volume 65 Issue 2 February 1967 pp 104-118
The flux of He3 nuclei and the ratio He3/(He3+He4) in the low energy primary cosmic radiation have been determined using a stack of nuclear emulsions exposed at 3·1 g. cm.−2 of atmospheric depth from Fort Churchill, Canada, in June 1963. The grain-density
Volume 65 Issue 4 April 1967 pp 219-226
The effect of ionisation loss, on the energy spectra of cosmic ray nuclei undergoing Fermi acceleration, has been studied using an analytic expression derived for the energy spectra of the nuclei undergoing acceleration. The spectra thus obtained have negative slopes which become steeper with increasing charge of the nucleus. In cases where the rate of acceleration is slow, solar modulation effects have been superimposed on the above spectra and it is found that the resulting spectral shapes can be fitted with recent satellite measurements for the energy spectra of various groups of cosmic ray nuclei at low energies.
Volume 70 Issue 5 November 1969 pp 201-220
A detailed study of the composition and energy spectra of heavy nuclei of charge Z⩾3 in the primary cosmic rays has been made during the period of low solar activity, using two stacks of nuclear emulsions exposed in balloon flights from Fort Churchill, Canada, in June 1963. Each of the stacks was composed of 120 nuclear emulsions of three different sensitivities and was exposed at about 3·5 g. cm.−2 of residual air for about 11.1 hr. Reliable resolution of charges of nuclei from lithium to oxygen was obtained; for heavier nuclei, charge groups were determined. From the analysis of 793 tracks of nuclei with Z⩾3, results on the following aspects were obtained:
The differential energy spectra of L (Z=3–5), M (Z=6–9) and H (Z=10–28) nuclei were measured in the energy intervel 150–600 MeV/nucleon; integral fluxes were obtained for energy >600 MeV/nucleon;
The energy dependence of the L/M ratio at the top of the atmosphere was determined; the ratios were obtained as 0·45 ± 0·06 and 0·29 ± 0·03 in the energy intervals of 200–575, and >575 MeV/nucleon respectively;
Relative abundances of individual nuclei of Li, Be, B, C, N and O at the top of the atmosphere were determined as 36, 29, 55, 100, 60 and 106 respectively in the energy interval 150–600 MeV/nucleon; corresponding values were also obtained for energy >600 MeV/nucleon.
The differential fluxes of multiply charged nuclei measured by us and by other investigators were used to determine the solar modulation between solar maximum to solar minimum. It was found that solar modulation of the fluxes of M and He nuclei were consistent with R
The implications of these results are discussed.