Forbush decrease(FD),discovered by Scott E.Forbush about 80 years ago,is referred to as the non-repetitive short-term depression in Galactic cosmic ray(GCR)flux,presumed to be associated with large-scale perturbations...Forbush decrease(FD),discovered by Scott E.Forbush about 80 years ago,is referred to as the non-repetitive short-term depression in Galactic cosmic ray(GCR)flux,presumed to be associated with large-scale perturbations in solar wind and interplanetary magnetic field(IMF).It is the most spectacular variability in the GCR intensity which appears to be the compass for investigators seeking solar-terrestrial relationships.The method of selection and validation of FD events is very important to cosmic ray(CR)scientists.We have deployed new computer software to determine the amplitude and timing of FDs from daily-averaged CR data at Oulu Neutron Monitor station.The code selected 230 FDs between 1998 and 2002.In an attempt to validate the new FD automated catalog,the relationship between the amplitude of FDs,and IMF,solar wind speed(SWS)and geomagnetic storm indices(Dst,kp,ap)is tested here.A two-dimensional regression analysis indicates significant linear relationship between large FDs(CR(%)≤-3)and solar wind data and geomagnetic storm indices in the present sample.The implications of the relationship among these parameters are discussed.展开更多
The glitch size,△ν/ν, inter-glitch time interval, ti, and frequency of glitches in pulsars are key parameters in discussing glitch phenomena. In this paper, the glitch sizes and inter-glitch time intervals are stat...The glitch size,△ν/ν, inter-glitch time interval, ti, and frequency of glitches in pulsars are key parameters in discussing glitch phenomena. In this paper, the glitch sizes and inter-glitch time intervals are statistically analyzed in a sample of 168 pulsars with a total of 483 glitches. The glitches are broadly divided into two groups. Those with △ν/ν< 10^-7 are regarded as small size glitches, while those with△ν/ν≥ 10^-7 are considered as relatively large size glitches. In the ensemble of glitches, the distribution of△ν/ν is seen to be bimodal as usual. The distribution of inter-glitch time intervals is unimodal and the interglitch time intervals between small and large size glitches are not significantly different from each other.This observation shows that inter-glitch time intervals are size independent. In addition, the distribution of the ratio △ν/ν: tiin both small and large size glitches has the same pattern. This observation suggests that a parameter which depends on time, which could be the spin-down rate of a pulsar, plays a similar role in the processes that regulate both small and large size glitches. Equally, this could be an indication that a single physical mechanism, which could produce varying glitch sizes at similar time-intervals, could be responsible for both classes of glitch sizes.展开更多
We present the results of an investigation of the relation between space-weather parameters and cosmic ray(CR)intensity modulation using algorithm-selected Forbush decreases(FDs)from Moscow(MOSC)and Apatity(APTY)neutr...We present the results of an investigation of the relation between space-weather parameters and cosmic ray(CR)intensity modulation using algorithm-selected Forbush decreases(FDs)from Moscow(MOSC)and Apatity(APTY)neutron monitor(NM)stations during solar cycle 23.Our FD location program detected 408 and 383 FDs from MOSC and APTY NM stations respectively.A coincident computer code employed in this work detected 229 FDs that were observed at the same Universal Time(UT)at the two stations.Out of the 229 simultaneous FDs,we formed a subset of 139 large FDs(%)≤-4 at the MOSC station.We performed a two-dimensional regression analysis between the FD magnitudes and the space-weather data on the two samples.We find that there were significant space-weather disturbances at the time of the CR flux depressions.The correlation between the space-weather parameters and decreases in galactic cosmic ray(GCR)intensity at the two NM stations is statistically significant.The implications of the present space-weather data on CR intensity depressions are highlighted.展开更多
The abrupt aperiodic modulation of cosmic ray(CR)flux intensity,often referred to as Forbush decrease(FD),plays a significant role in our understanding of the Sun-Earth electrodynamics.Accurate and precise determinati...The abrupt aperiodic modulation of cosmic ray(CR)flux intensity,often referred to as Forbush decrease(FD),plays a significant role in our understanding of the Sun-Earth electrodynamics.Accurate and precise determinations of FD magnitude and timing are among the intractable problems in FD-based analysis.FD identification is complicated by CR diurnal anisotropy.CR anisotropy can increase or reduce the number and amplitude of FDs.It is therefore important to remove its contributions from CR raw data before FD identification.Recently,an attempt was made,using a combination of the Fourier transform technique and FD-location machine,to address this.Thus,two FD catalogs and amplitude diurnal variation(ADV)were calculated from filtered(FD1 and ADV)and raw(FD2)CR data.In the current work,we test the empirical relationship between FD1,FD2,ADV and solar-geophysical characteristics.Our analysis shows that two types of magnetic fields-interplanetary and geomagnetic(Dst)-govern the evolution of CR flux intensity reductions.展开更多
文摘Forbush decrease(FD),discovered by Scott E.Forbush about 80 years ago,is referred to as the non-repetitive short-term depression in Galactic cosmic ray(GCR)flux,presumed to be associated with large-scale perturbations in solar wind and interplanetary magnetic field(IMF).It is the most spectacular variability in the GCR intensity which appears to be the compass for investigators seeking solar-terrestrial relationships.The method of selection and validation of FD events is very important to cosmic ray(CR)scientists.We have deployed new computer software to determine the amplitude and timing of FDs from daily-averaged CR data at Oulu Neutron Monitor station.The code selected 230 FDs between 1998 and 2002.In an attempt to validate the new FD automated catalog,the relationship between the amplitude of FDs,and IMF,solar wind speed(SWS)and geomagnetic storm indices(Dst,kp,ap)is tested here.A two-dimensional regression analysis indicates significant linear relationship between large FDs(CR(%)≤-3)and solar wind data and geomagnetic storm indices in the present sample.The implications of the relationship among these parameters are discussed.
文摘The glitch size,△ν/ν, inter-glitch time interval, ti, and frequency of glitches in pulsars are key parameters in discussing glitch phenomena. In this paper, the glitch sizes and inter-glitch time intervals are statistically analyzed in a sample of 168 pulsars with a total of 483 glitches. The glitches are broadly divided into two groups. Those with △ν/ν< 10^-7 are regarded as small size glitches, while those with△ν/ν≥ 10^-7 are considered as relatively large size glitches. In the ensemble of glitches, the distribution of△ν/ν is seen to be bimodal as usual. The distribution of inter-glitch time intervals is unimodal and the interglitch time intervals between small and large size glitches are not significantly different from each other.This observation shows that inter-glitch time intervals are size independent. In addition, the distribution of the ratio △ν/ν: tiin both small and large size glitches has the same pattern. This observation suggests that a parameter which depends on time, which could be the spin-down rate of a pulsar, plays a similar role in the processes that regulate both small and large size glitches. Equally, this could be an indication that a single physical mechanism, which could produce varying glitch sizes at similar time-intervals, could be responsible for both classes of glitch sizes.
文摘We present the results of an investigation of the relation between space-weather parameters and cosmic ray(CR)intensity modulation using algorithm-selected Forbush decreases(FDs)from Moscow(MOSC)and Apatity(APTY)neutron monitor(NM)stations during solar cycle 23.Our FD location program detected 408 and 383 FDs from MOSC and APTY NM stations respectively.A coincident computer code employed in this work detected 229 FDs that were observed at the same Universal Time(UT)at the two stations.Out of the 229 simultaneous FDs,we formed a subset of 139 large FDs(%)≤-4 at the MOSC station.We performed a two-dimensional regression analysis between the FD magnitudes and the space-weather data on the two samples.We find that there were significant space-weather disturbances at the time of the CR flux depressions.The correlation between the space-weather parameters and decreases in galactic cosmic ray(GCR)intensity at the two NM stations is statistically significant.The implications of the present space-weather data on CR intensity depressions are highlighted.
文摘The abrupt aperiodic modulation of cosmic ray(CR)flux intensity,often referred to as Forbush decrease(FD),plays a significant role in our understanding of the Sun-Earth electrodynamics.Accurate and precise determinations of FD magnitude and timing are among the intractable problems in FD-based analysis.FD identification is complicated by CR diurnal anisotropy.CR anisotropy can increase or reduce the number and amplitude of FDs.It is therefore important to remove its contributions from CR raw data before FD identification.Recently,an attempt was made,using a combination of the Fourier transform technique and FD-location machine,to address this.Thus,two FD catalogs and amplitude diurnal variation(ADV)were calculated from filtered(FD1 and ADV)and raw(FD2)CR data.In the current work,we test the empirical relationship between FD1,FD2,ADV and solar-geophysical characteristics.Our analysis shows that two types of magnetic fields-interplanetary and geomagnetic(Dst)-govern the evolution of CR flux intensity reductions.
