Abstract
Abstract. An understanding of how the heliosphere modulates galactic cosmic ray (GCR) fluxes and spectra is important, not only for studies of their origin, acceleration and propagation in our galaxy, but also for predicting their effects (on technology and on the Earth's environment and organisms) and for interpreting abundances of cosmogenic isotopes in meteorites and terrestrial reservoirs. In contrast to the early interplanetary measurements, there is growing evidence for a dominant role in GCR shielding of the total open magnetic flux, which emerges from the solar atmosphere and enters the heliosphere. In this paper, we relate a strong 1.68-year oscillation in GCR fluxes to a corresponding oscillation in the open solar magnetic flux and infer cosmic-ray propagation paths confirming the predictions of theories in which drift is important in modulating the cosmic ray flux. Key words. Interplanetary physics (Cosmic rays, Interplanetary magnetic fields)
Highlights
The energy and composition spectra of Galactic Cosmic Rays (GCRs) provide unique information on astrophysical processes, but interpretation is complicated by the effects of magnetic fields which influence the particle’s trajectory, within the heliosphere (e.g. Ginzburg, 1996)
We notice an interesting fact, that is, the alternate peaked and rounded maxima seen in the neutron GCR flux time series, successfully attributed to the polarity-dependent drift component of the propagation mechanisms of cosmic rays in the heliosphere, is seen in the variation of the two 1-AU open flux estimates presented here
This implies that the Sun has, as well as a twenty-two-year cycle in the direction of its dipolar field, a twenty-two-year pattern in the quantity of open field lines threading a sphere passing at 1 AU
Summary
The energy and composition spectra of Galactic Cosmic Rays (GCRs) provide unique information on astrophysical processes, but interpretation is complicated by the effects of magnetic fields which influence the particle’s trajectory, within the heliosphere (e.g. Ginzburg, 1996). Wibberenz et al (2002) assumed that the radial diffusion coefficient scales as some power of the magnitude of the IMF and invoked continuous recovery processes (related to particle entry into depleted regions of the heliosphere by drift and diffusion), to develop a simple model which seems to map cosmic ray intensity variations very well over the last four solar cycles (Wibberenz and Cane, 2000; Wibberenz et al, 2002).
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