On the Relationship of the 27-day Variations of the Solar Wind Velocity and Galactic Cosmic Ray Intensity in Minimum Epoch of Solar Activity |
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| Authors: | M V Alania R Modzelewska A Wawrzynczak |
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| Institution: | (1) Department of Physics, Govt. Model Science College (Autonomous), Jabalpur, Madya Pradesh, 482 001, India;(2) Computer and I.T. Section, Tropical Forest Research Institute, Mandla Road, P.O. RFRC, Jabalpur, 482 021, Madya Pradesh, India;(3) Present address: C-4, Anumit Enclave, Phase-I, Pachpedi, Near Maihar House, South Civil Line, Jabalpur, Madya Pradesh, 482 001, India; |
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| Abstract: | We study the relationship of the 27-day variations of the galactic cosmic ray intensity with similar variations of the solar
wind velocity and the interplanetary magnetic field based on observational data for the Bartels rotation period # 2379 of
23 November 2007 – 19 December 2007. We develop a three-dimensional (3-D) model of the 27-day variation of galactic cosmic
ray intensity based on the heliolongitudinally dependent solar wind velocity. A consistent, divergence-free interplanetary
magnetic field is derived by solving Maxwell’s equations with a heliolongitudinally dependent 27-day variation of the solar
wind velocity reproducing in situ observations. We consider two types of 3-D models of the 27-day variation of galactic cosmic ray intensity, i) with a plane heliospheric neutral sheet, and ii) with the sector structure of the interplanetary magnetic field. The theoretical calculations show that the sector structure
does not significantly influence the 27-day variation of galactic cosmic ray intensity, as had been shown before, based on
observational data. Furthermore, good agreement is found between the time profiles of the theoretically expected and experimentally
obtained first harmonic waves of the 27-day variation of the galactic cosmic ray intensity (with a correlation coefficient
of 0.98±0.02). The expected 27-day variation of the galactic cosmic ray intensity is inversely correlated with the modulation
parameter ζ (with a correlation coefficient of −0.91±0.05), which is proportional to the product of the solar wind velocity
V and the strength of the interplanetary magnetic field B (ζ∼VB). The high anticorrelation between these quantities indicates that the predicted 27-day variation of the galactic cosmic
ray intensity mainly is caused by this basic modulation effect. |
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