Modulation of cosmic ray protons and helium nuclei near solar maximum
Abstract
Balloon observations of proton and helium spectra in 1970, 1971, and 1972, which extend previous work for the period 1965-1969, reveal a factor of ∼1.85 deviation from a single-valued regression at low rigidities. This deviation decreases with increasing rigidity for both species. The period 1969-1970 is unique because time variations at low and high energies were anticorrelated. When satellite observations are used to extend the balloon observations to energies below 100 MeV/nucleon, the proton spectrum shows a steeper slope in 1970 and 1972 than the characteristic J=AT spectrum observed during 1965-1969. The slope of the helium spectrum became continuously flatter during the same period (1970-1972). Computer-generated spectra based on simple two-parameter modulation models describe the basic features of the observations if one of the variable parameters is used to characterize the rigidity dependence of the diffusion coefficient. On the other hand, models that do not allow such a variation are not consistent with the observations.
- Publication:
-
Journal of Geophysical Research
- Pub Date:
- October 1974
- DOI:
- 10.1029/JA079i028p04127
- Bibcode:
- 1974JGR....79.4127R
- Keywords:
-
- Alpha Particles;
- Cosmic Rays;
- Energy Spectra;
- Modulation;
- Proton Flux Density;
- Solar Activity Effects;
- Astronomical Models;
- Balloon-Borne Instruments;
- Computer Techniques;
- Hodoscopes;
- Hysteresis;
- Long Term Effects;
- Regression Analysis;
- Particles and Fields-Interplanetary Space: Cosmic rays;
- Particles and Fields-Interplanetary Space: Solar wind magnetic fields