Fig. 1: Event rate (day^-1 m^-2 sr^-1) in horizontal coordinates. The dotted curves indicate contours of constant declination, while the arrows indicate the apparent motion of stars with the rotation of Earth.
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Fig. 1: Event rate (day^-1 m^-2 sr^-1) in horizontal coordinates. The dotted curves indicate contours of constant declination, while the arrows indicate the apparent motion of stars with the rotation of Earth. |
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| 1d_anisotropy_v10_deg_mod.eps |
| Fig. 2: (a) Track-type right ascension projection plot. (b) Zenith-type plot. The error bars represent statistical error. The solid curve in each frame is the best fit of the first two harmonic functions. The dashed curve (almost overlapping the solid curve) is the first two harmonics after subtracting the atmospheric contribution. |
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| amp_phase_vs_energy_v7.eps |
| Fig. 3: Amplitude and phase of the first harmonic fit to the zenith-type plots from various cosmic ray experiments. The energy in the horizontal axis is either the median or the log-mean energy. Circles: muon detectors. Squares: extensive air shower array. Filled circles: SK-I. |
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| skymap_eq_and_gal_v2.eps |
| Fig. 4: (a) & (b) Sky map of the anisotropy in equatorial coordinates. (c) & (d) in galactic coordinates. The first column -- (a) & (c) -- show the fractional deviation from isotropy, while the second column -- (b) & (d) is the standard deviation of this variation. The sky is divided into 10x10 degree cells in equatorial coordinates; the galactic plot is obtained by a transformation of the equatorial map to galactic coordinates. Gouraud smoothing was applied to make the trends visually clear. Declination below 53.58 degrees south always lie below the horizon and are thus invisible to the detector. The solid red and blue curves show the excess and deficit cones obtained using a clustering algorithm applied to the data. The dashed curves in (a) and (b) show the excess and deficit cones from the NFJ model. The red, dashed, horizontal line in (c) and (d) indicates the direction of the orion arm. |
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| amp_vs_phase_chi2_1sigma_contour_yearly_polar_v3.eps |
| Fig. 5: The w-parameter 68% confidence level regions (delta-chi^2 = 2.3) of the amplitude and phase of the first harmonic function fit to yearly track-type anisotropy plots. The radial distance from the origin is the first harmonic amplitued, while the counterclockwise angle from RA = 0 deg. is the right ascension at maximum. The regions are labeled by the corresponding year. The label "Combined" indicates the contour from the 5-year combined data set. |
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| 1d_anisotropy_v10_hr.eps |
| Fig. 6: (a) Relative muon rate as a function of local sidereal time (i.e. zenith-type map), in hours right ascension. (b) Relative muon rate as a function of local solar hour. (c) Relative muon rate as a function of hours, pseudo-sidereal time. The curve in each frame is the best fit of the first two harmonic functions to the data. |
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| phasor_cg_v8.eps |
| Fig. 7: Phasor diagrams showing the result of subtracting the atmospheric and Compton-Getting effects. The length of an arrow represents the amplitude of the first harmonic component, while the angle measured counter clockwise from phi = 0 deg. is the phase at maximum. (a) Atmospheric effect, (b) Compton-Getting effect assuming cosmic ray rest frame moving with the local standard of rest, and (c) same as (b), but moving with the local interstellar medium. In each plot, the vector D indicates the uncorrected amplitude and phase, while the vector -B^prime, -V_LSR, and -V_ISM are corrections for the atmospheric and Compton-Getting effects. The vector A is the amplitude of the solar variation, B is that of the pseudo-sidereal variation, and C is the amplitude of the true sidereal variation (i.e. corrected for various effects). |
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| 2d_ps_and_cg_correction_v3.eps |
| Fig. 8: Anisotropy introduced by: (a) the atmospheric effect; (b) the Compton-Getting effect assuming that the bulk cosmic ray motion is the same as the local standard of rest; (c) same as (b), but the motion is assumed to be the same as that of the the neutral interstellar matter. The contour values indicate fractional deviation from isotropy, in units of 10^-4. The white region below declination -53.58 deg. is always below the horizon. Note that the filter applied to the data projects the anisotropy shown in (b) and (c) onto the equatorial plane. |
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| muon_rate_vs_yymm_obs_and_calc_muyn_eq_1.eps |
| Fig. 9: (a) Variation in the muon rate relative to the mean for each month of SK-I. (b) The variation seen at Matsushiro during the same period. The solid curve in each frame is the predicted rate variation based on a numerical model with input data from profile atmospheric temperature measurement. |
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| change_in_rel_rate_sk_mat_muyn_eq_1.eps |
| Fig. 10: The correlation between (delta-I / I)n,n-1 in SK vs. Matsushiro. Delta-I / I is the relative rate variation of a given month; the notation (delta-I / I)n,n-1 indicates the difference of this quantity between month n and n-1. Gamma = 0.855 is the linear correlation coefficient between the two data (60 degrees of freedom), while beta = 2.03 +/- 0.05 is the best fit slope. |