Long-term modulation of cosmic rays in interplanetary magnetic turbulence

Miscellaneous · Sun Jan 01 00:00:00 EST 1989

OSTI ID:6003372

Chen, J

Long-term modulation of galactic cosmic rays in interplanetary magnetic field (IMF) turbulence is a fundamental subject for understanding the connection between cosmic ray transport and solar activity. The discovery of a new cosmic ray modulation phenomenon is reported. Analysis of neutron monitor data has revealed that the difference in amplitude of the cosmic ray diurnal anisotropy for IMF sectors directed toward and away from the Sun displays a solar cycle variation. Neutron monitor data recorded at Climax, Deep River, Hyancayo, Kiel, Mt. Washington, and Swarthmore/Newark over the period 1957 to 1988 show that the amplitude difference varied between approximately 0.1 to -0.1 percent, with peaks in 1960, 1972, and 1982. A theoretical expression for this difference was derived from a three-dimensional model. Analysis also showed that the latitudinal density gradient of cosmic rays changed between 1.6 and -1.6 percent/AU with a solar cycle variation, which may produce the variation of the amplitude difference of the cosmic ray diurnal anisotropy. In order to investigate the underlying physical mechanism which produces the observed effect, it was necessary to develop a new analytical technique for calculating energy spectra of the IMF turbulence. The cosmic ray scattering mean free path was calculated from the measured spectrum, solar wind speed, and mean magnetic field by using the quasilinear theory in the slab model. This transport parameter displays a solar cycle variation and is proportional to the amplitude difference of the cosmic-ray diurnal anisotropy.

• Research Organization: Delaware Univ., Newark, DE (USA)
• OSTI ID: 6003372
• Resource Relation: Other Information: Ph.D. Thesis
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC RADIATION
MODULATION
INTERPLANETARY MAGNETIC FIELDS
TURBULENCE
SOLAR ACTIVITY
RADIATION TRANSPORT
ANISOTROPY
DAILY VARIATIONS
ENERGY SPECTRA
EXPERIMENTAL DATA
MATHEMATICAL MODELS
MEAN FREE PATH
SCATTERING
SOLAR WIND
VELOCITY
DATA
INFORMATION
IONIZING RADIATIONS
MAGNETIC FIELDS
NUMERICAL DATA
RADIATIONS
SPECTRA
VARIATIONS
640101* - Astrophysics & Cosmology- Cosmic Radiation