A study of daily variation in cosmic ray intensity during high/low amplitude days |
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Authors: | Rajesh K Mishra Rekha Agarwal Mishra |
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Institution: | (1) Computer and I.T. Section, Tropical Forest Research Institute, P.O. RFRC, Mandla Road, Jabalpur, 482 021, India;(2) Department of Physics, Govt. Model Science College (Autonomous), Jabalpur, 482 001, India |
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Abstract: | A detailed study has been conducted on the long-term changes in the diurnal, semi-diurnal and tri-diurnal anisotropies of
cosmic rays in terms of the high/low amplitude anisotropic wave train events (HAE/LAE) during the period 1981–94 using the
neutron monitor data from Deep River Neutron Monitoring Station. In all, 38 HAE and 28 LAE cases have been studied. An inter-comparison
of the first three harmonics during these events has been made so as to understand the basic reason for the occurrence of
these types of events. It has been observed that the phase of diurnal anisotropy shifts towards earlier hours for HAEs and
it shifts towards earlier hour as compared to 18-h direction for LAEs. For semi-diurnal anisotropy, phase remains statistically
the same for both HAE and LAE. In the case of tri-diurnal anisotropy, phase is evenly distributed for both types of events.
The interplanetary magnetic field (IMF) and solar wind plasma (SWP) parameters during these events are also investigated.
It has also been observed that HAE/LAEs are weakly dependent on high-speed solar wind velocity. The two types of solar wind
streams (corotating streams and flare-generated streams) produce significant deviations in cosmic ray intensity during HAE/LAE.
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Keywords: | Cosmic ray diurnal semi-diurnal anisotropy high-speed solar wind streams interplanetary magnetic field |
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