Interplanetary turbulences causing unusual anisotropic wave trains in cosmic rays

The various observed harmonics of the cosmic ray variation may be understood on a unified basis if the free space cosmic ray anisotropy is non-sinusoidal in form. The major objective of this paper is to study the first three harmonics of high amplitude wave trains of cosmic ray intensity over the period 1991-1994 for Deep River Neutron Monitoring Station. The main characteristic of these events is that the high amplitude wave trains shows a maximum intensity of diurnal component in a direction earlier than 1800 Hr/co-rotational direction. It is noticed that these events are not caused either by the high-speed solar wind streams or by the sources on the Sun responsible for producing these streams such as polar coronal holes. The direction of semi-diurnal anisotropy shows negative correlation with Bz. The occurrence of high amplitude events is dominant for the positive polarity of Bz component of IMF. The diurnal amplitude of these events shows a negative and the time of maximum shows a weak correlation with disturbance storm time index Dst. The direction of tri-diurnal anisotropy of these events is found to significantly correlate with geomagnetic activity index Ap.