Abstract:The cosmic ray (CR) intensity data recorded with Goose Bay Neutron Monitoring Station have been investigated on 60 quietest days (QD) in a year for studying the variation in tri diurnal anisotropy during solar cycle 21 and 22. It has been observed that in spite of abrupt change in the amplitude and phase of tri-diurnal anisotropy in CR intensity, the amplitude is quite significant throughout period of investigation with small amplitude during 1981 and 1990. Further, the phase shift to earlier hours during 1990-91 showing the dependence on the polarity of solar magnetic field, which is attributed to drift effect. Thus, the tri-diurnal anisotropy clearly shows 11 year type variation at mid-latitude neutron monitoring station.
The cosmic ray (CR) intensity data recorded in Deep River Neutron Monitoring Station have been investigated on quietest days (QD) for third harmonics of daily variation during solar cycles 21 and 22. It has been observed that in spite of abrupt change in the amplitude and phase of tri-diurnal anisotropy in CR intensity, the amplitude is quite significant throughout the period of investigation with larger amplitude during the years 1980 and 1985. Thus, tri-diurnal anisotropy clearly shows 11-year variation at the mid latitude neutron monitoring station.
The aim of this work is comparative study the long term variation in third and fourth harmonics of daily variation of cosmic intensity on sixty quietest days in a year using the data of equatorial and midlatitude neutron monitoring stations have been investigated for studying comparative variation in third harmonic of cosmic ray intensity during solar cycle twenty one and twenty two.It has been observed that in spite of the abrupt changes in the amplitude and phase of the tri-diurnal anisotropy in cosmic ray intensity, the amplitude of third harmonic is observed relatively larger during the declining phase of solar cycle twenty one and twenty two as it is observed during the declining phase of solar cycle twenty at equatorial stations. Further ,the amplitude of third harmonics of daily variation on quiet days in significantly low value during the 1981 and 1990 at mid-latitude stations. Furthermore the phase in third harmonics shift to earlier over during the period 1990-91 showing the dependence on the polarity of solar magnetic filed, which is attributed to drift effect at midlatitude neutron monitoring stations.
The aim of this work is to study the long term variation in third harmonics of cosmic ray intensity on sixty quietest days in a year using the data of high latitude and low latitude neutron monitoring stations during the solar cycle 20-22. It has been observed that in spite of the abrupt change in the amplitude and phase of third harmonic of cosmic ray intensity, the amplitude of third harmonics is relatively larger during the solar cycle 21 as it is observed during the declining phase of earlier solar cycle 20.Therefore this enhancement explicit point out 11 year periodicity in third harmonics of cosmic ray intensity at equatorial neutron monitoring stations. Further, the phase shift to later hours during the year 1990 showing the dependence on the polarity of solar magnetic field, which is attributed to drift effect at high latitude neutron monitoring station
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