Significance of interplanetary plasma and magnetic field features in modulating cosmic rays
نویسندگان
چکیده
Abstract This work deals with the time evolution of the three harmonics of the unusual diurnal variation of cosmic ray intensity during high amplitude anisotropic wave trains. The relation of these harmonics to interplanetary parameters such as Dst-index, Ap-index, solar wind speed and interplanetary magnetic field (Bz) is investigated in order to found the possible origin of these anisotropic wave trains and to develop a suitable theoretical model. The first three harmonics of high amplitude anisotropic wave trains of cosmic ray intensity over the period 1991-1994 have been investigated for Deep River neutron monitoring station. It is noteworthy that the amplitude of all the three harmonics remains high whereas, the direction of first harmonic shift towards earlier hours and towards later hours for second and third harmonic compared to quite day annual average. The Bz component of interplanetary magnetic field, the disturbance storm time index (Dst) and geomagnetic activity index (Ap) shows good impact on direction of first harmonic, amplitude of third harmonic and direction of third harmonic respectively. High amplitude anisotropic wave train events seem to weakly dependent on solar wind velocity.
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