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Astrophys Space Sci (2010) 325: 185193 DOI 10.1007/s10509-009-0181-9
O R I G I NA L A RT I C L E
On the relationship of cosmic ray intensity with solar, interplanetary, and geophysical parameters
K.A. Firoz D.V. Phani Kumar K.-S. Cho
Received: 23 June 2009 / Accepted: 17 October 2009 / Published online: 12 November 2009 Springer Science+Business Media B.V. 2009
Abstract The ux rate of cosmic rays incident on the Earths upper atmosphere is modulated by the solar wind and the Earths magnetic eld. The amount of solar wind is not constant due to changes in solar activity in each solar cycle, and hence the level of cosmic ray modulation varies with solar activity. In this context, we have investigated the variability and the relationship of cosmic ray intensity with solar, interplanetary, and geophysical parameters from January 1982 through December 2008. Simultaneous observations have been made to quantify the exact relationship between the cosmic ray intensity and those parameters during the solar maxima and minima, respectively. It is found that the stronger the interplanetary magnetic eld, solar wind plasma velocity, and solar wind plasma temperature, the weaker the cosmic ray intensity. Hence, the lowest cosmic ray intensity has good correlations with simultaneous solar parameters, while the highest cosmic ray intensity does not. Our results show that higher solar activity is responsible for a higher geomagnetic effect and vice versa.
Keywords Cosmic ray intensity Solar parameters
Modulation
1 Introduction
The energetic particles traditionally known as cosmic rays are believed to be produced by a number of different sources, such as the remnants of supernovae, neutron stars,
K.A. Firoz ( ) D.V.P. Kumar K.-S. Cho
Solar and Space Weather Research Group, Korea Astronomy and Space Science Institute, 61-1, Whaam Dong, Yuseong-gu, Daejeon, 305-348, Republic of Koreae-mail: [email protected]
and black holes and sometimes from the more exotic objects from the sun and stars and also from the abandoned objects of radio galaxies. They undergo collisions with atoms of the upper atmosphere and produce a cascade of secondary particles that shower down through the atmosphere onto the surface of the Earth. Almost 90% of all the incoming cosmic ray particles are protons, about 9% are helium nuclei, and about 1% are electrons (see, e.g., Hess 1912; Kohlhorster 1913;...