The acceleration and propagation of solar cosmic rays as deduced from the relative abundance of protons to helium nuclei

✍ Scribed by Kunitomo Sakurai

• Publisher: Springer
• Year: 1971
• Tongue: English
• Weight: 488 KB
• Volume: 17
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00150047

✦ Synopsis

Except for protons, the chemical composition of solar cosmic rays is very similar to the abundance of the elements at the photosphere of the Sun. If we consider the relative abundance ratio of protons to a-particles (P/a) at constant rigidity, this ratio is highly variable from one solar cosmic ray event to another. This ratio observed at the Earth, however, decreases monotonically with time from the onset of solar flares and, furthermore, is dependent on the heliocentric distance of the parent flares from the central meridian of the solar disk. P/a's which have been measured before the onset of SC geomagnetic storms change from 1.5 to 50 or more, being a function of the westward position of the source from the east limb of the Sun. These variations with respect to time and heliocentric distance suggest that the propagation of solar cosmic rays is strongly modulated in the interplanetary space. The major part of the a-particles seem to propagate as if they are trapped within the magnetic clouds which produce SC geomagnetic and cosmic ray storms at the earth.

The chemical composition and rigidity spectra of solar cosmic rays suggest that solar cosmic rays are mainly accelerated by the Fermi mechanism in solar flares. The observed variation of P/c~'s is produced mainly through the difference between the propagation characteristics of protons and a-particles.

* NAS-NRC Associate with NASA.