Anomalous helium component in the heliosphere: The 1965 versus the 1972-1977 solar minimum

Journal Article · Tue Nov 15 04:00:00 EST 1983 · Astrophys. J., Lett. Ed.; (United States)

DOI:https://doi.org/10.1086/184157· OSTI ID:5202945

Garcia-Munoz, M; Pyle, K R; Simpson, J A

The anomalous /sup 4/He component (hereafter He(A)) was first observed in the galactic cosmic-ray helium spectrum at energies below about 60 MeV per nucleon in 1972 at the beginning of the extended period of minimum solar modulation, 1972-1977, after which period it again disappeared as solar modulation increased in the new solar activity cycle. This component was not apparent during the 1965 solar minimum. We find that the helium spectrum measured during a short interval of enhanced modulation in 1974-1975 shows the same level as the He spectrum measured during 1965. This fact demonstrates that the absence of He(A) in 1965 can be explained as the consequence of a greater level of solar modulation at low energies in 1965 than in most of the 1972-1977 solar minimum. We conclude that He(A) may be present at all times in the outer heliosphere and be observable at successive solar minima if the residual solar modulation is sufficiently low, as in most of the 1972-1977 minimum.

• Research Organization: Enrico Fermi Institute, University of Chicago
• OSTI ID: 5202945
• Journal Information: Astrophys. J., Lett. Ed.; (United States), Journal Name: Astrophys. J., Lett. Ed.; (United States) Vol. 274:2; ISSN AJLEA
• Country of Publication: United States
• Language: English

Related Subjects

640101* -- Astrophysics & Cosmology-- Cosmic Radiation
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
COSMIC RADIATION
ENERGY SPECTRA
EVEN-EVEN NUCLEI
HELIUM 4
HELIUM ISOTOPES
IONIZING RADIATIONS
ISOTOPES
LIGHT NUCLEI
NUCLEI
RADIATIONS
SOLAR ACTIVITY
SOLAR WIND
SPECTRA
STABLE ISOTOPES
TELESCOPE COUNTERS