Effect of Polarity Reversal on Third Harmonics of Cosmic Ray Intensity on Quiet Days

Abstract

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.

Comparative Study of Higher Harmonics of Cosmic Ray Intensity on Quiet Days Between Equatorial and Mid-Latitude Neutron Monitoring Stations

“…Whereas in both the cases during the succeeding years, i.e., 1980-81 and 1991-92, the change in the phase of tri-diurnal anisotropy of CR intensity has been found quite significant [14,15]. It is clear that there exist a 11 year type of variation in third harmonics of CR intensity on QD due to the variation of solar activity [16][17][18]. The polarity dependence of the phase shift change has been interpreted as a result due to the change of CR density distribution in space caused by the difference of CR drift motion in the positive and negative polarity state.…”

“…The polarity dependence of the phase shift change has been interpreted as a result due to the change of CR density distribution in space caused by the difference of CR drift motion in the positive and negative polarity state. The existence of polarity dependence in the tri-diurnal variation may be defined as the state is positive, when the magnetic field is away from the sun at the north pole and magnetic field toward the Sun at the south pole, the state is called negative, when the polar magnetic field are reversed [17,18].…”

Effect of solar Poloidal magnetic field reversal on tri-diurnal anisotropy of cosmic ray intensity on quiet days.

“…Furthermore, it is quite apparent from Fig. 4, that there is no systematic change in the phase of fourth harmonics, the phase in the year 1981 and 1992 has occurred in the same direction, which may be indicate likely 11 year type variation at Deep River Neutron monitoring station [16].…”

“…1980-81 and 1991-92, the change in the phase of tri-diurnal anisotropy of CR intensity has been found quite significant [14,15]. It is clear that there exist a 11 year type of variation in third harmonics of CR intensity on QD due to the variation of solar activity [16]. Furthermore, it is quite apparent from Fig.…”

“…The polarity dependence of the phase shift change has been interpreted as a result due to the change of CR density distribution in space caused by the difference of CR drift motion in the positive and negative polarity state. The existence of polarity dependence in the tri-diurnal variation may be defined as the state is positive, when the magnetic field is away from the sun at the north pole and toward the Sun at the south pole, while it is called negative, when the polar magnetic field are reversed[17].The yearly average amplitude and phase of fourth harmonics of daily variation on quiet days for Deep River and Goose Bay Neutron Monitoring station have been plotted inFig. 4during the period 1978-94.…”