Enhanced Cosmic Ray Diurnal Variations in Mawson and Hobart Neutron Monitor and Underground Data Records

AbstractAnalysis of surface and underground detector data from Mawson and Hobart for the period 1982 to 1988 has revealed a number of episodes of enhanced diurnal variation lasting more than 5 days. A preliminary study of these enhancements shows that variations in the rigidity spectrum and in the upper limiting rigidity must be present to explain the phenomenon.

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PERIODICAL FLUCTUATION STUDIES OF COSMIC-RAY DIURNAL VARIATIONS DURING THE QUIET-SUN PERIOD 1962–64

Canadian Journal of Physics ◽

10.1139/p67-220 ◽

1967 ◽

Vol 45 (8) ◽

pp. 2733-2748 ◽

Cited By ~ 1

Author(s):

Masahiro Kodama

Keyword(s):

Diurnal Variation ◽

Solar Minimum ◽

Counting Rate ◽

Solar Rotation ◽

Rotation Period ◽

Cosmic Ray ◽

Diurnal Variations ◽

Statistical Studies ◽

Periodic Fluctuations ◽

Recurrence Tendency

Statistical studies of periodic fluctuations of the cosmic-ray diurnal variation have been performed, using neutron and meson component data obtained by the high-counting-rate cosmic-ray monitors at Deep River. The data cover an interval from May 1962 to October 1964, a period of descending solar activity ending near the solar minimum. It is shown that a 27-day recurrence tendency of the amplitude of the diurnal variation occasionally appears as well as shorter recurrent variations, ranging from one-half to one-sixth of the solar rotation period. The correlations of these fluctuations with some typical solar and terrestrial indices are examined in order to search for possible origins of the shorter recurrent variations. A possible connection with the Kp index exists.

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ATMOSPHERIC CONTRIBUTION TO THE DIURNAL VARIATION OF THE COSMIC-RAY MESON INTENSITY AT DEEP RIVER

Canadian Journal of Physics ◽

10.1139/p66-112 ◽

1966 ◽

Vol 44 (6) ◽

pp. 1329-1347 ◽

Cited By ~ 2

Author(s):

M. Bercovitch

Keyword(s):

Diurnal Variation ◽

Neutron Monitor ◽

Cosmic Ray ◽

Ground Level ◽

Barometric Pressure ◽

Atmospheric Temperature ◽

The Mean ◽

Variation Vector ◽

Best Fit ◽

Ground Level Air

We have established the correlation between the atmospheric temperature contribution to the diurnal variation observed by a meson monitor at Deep River and the diurnal variation of two easily and continuously observable atmospheric variables, the ground-level air temperature and the barometric pressure. The atmospheric meson diurnal variation vector is taken to be, on a statistical basis, A = M−RN, where M and N represent the observed meson-monitor and neutron-monitor diurnal variations and R is the factor of proportionality between the meson and neutron monitor responses to the primary anisotropy. It is found that A is proportional in amplitude to T, the ground-level temperature diurnal variation, and, further, that T and the barometric-pressure diurnal variation P are proportional in amplitude. The "best-fit" representation of A in terms of T and P is determined by minimizing the mean-square deviation between the daily vectors RN and (M−A). Where A = CtT + CpP, the best fit occurs when Ct = −0.0052%/ °C, Cp = 0.038%/mb, R = 0.47, and the phase of T is shifted by + 1.0 hour. These values apply to Deep River, where the original hourly meson data have been barometer-corrected using a coefficient of 0.16%/mb.

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The second spherical harmonic of the diurnal variation and the orientation of the interplanetary magnetic field

Canadian Journal of Physics ◽

10.1139/p68-397 ◽

1968 ◽

Vol 46 (10) ◽

pp. S973-S975 ◽

Cited By ~ 1

Author(s):

G. V. Skeipin ◽

P. A. Krivoshapkin ◽

G. F. Krymsky ◽

A. I. Kuzmin

Keyword(s):

Magnetic Field ◽

Diurnal Variation ◽

Interplanetary Magnetic Field ◽

Neutron Monitor ◽

Spherical Harmonic ◽

Cosmic Ray ◽

Vector Information ◽

Neutron Monitor Data ◽

Distribution Vector ◽

Monitor Data

The super neutron monitor data from Goose Bay and Deep River for 1965 have been analyzed to give month-to-month changes of the first and second harmonics of the solar-diurnal variation. Using these results together with various suppositions about the nature of the cosmic-ray distribution vector, information is obtained concerning the orientation of the interplanetary magnetic field.

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On the Rigidity Spectrum of Cosmic-Ray Variations within Propagating Interplanetary Disturbances: Neutron Monitor and SOHO/EPHIN Observations at ∼1–10 GV

The Astrophysical Journal ◽

10.3847/1538-4357/abd724 ◽

2021 ◽

Vol 908 (1) ◽

pp. 5

Author(s):

Anatoly Belov ◽

Athanasios Papaioannou ◽

Maria Abunina ◽

Mateja Dumbovic ◽

Ian G. Richardson ◽

...

Keyword(s):

Neutron Monitor ◽

Cosmic Ray ◽

Rigidity Spectrum

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On the possibility of a two-way solar anisotropy producing the cosmic-ray diurnal variation

Canadian Journal of Physics ◽

10.1139/p68-360 ◽

1968 ◽

Vol 46 (10) ◽

pp. S825-S827

Author(s):

M. Kodama ◽

K. Nagashima

Keyword(s):

Diurnal Variation ◽

High Altitude ◽

Experimental Evidence ◽

Sea Level ◽

Phase Difference ◽

Solar Rotation ◽

Theoretical Calculations ◽

Cosmic Ray ◽

Diurnal Variations ◽

Neutron Component

Two pieces of experimental evidence, which are inconsistent with the hypothesis of a one-way solar anisotropy as an interpretation of the cosmic-ray diurnal variation, are presented. The diurnal variation of the temperature-corrected meson component at Deep River was examined and compared with that of the neutron component. Both diurnal variations were averaged for each solar rotation from No. 1762 to No. 1787. If a one-way solar anisotropy is assumed, the time of maximum for neutrons should be about half an hour earlier than that for mesons at Deep River. However, the observations show that the phase difference between the two components is the reverse of that expected. Further evidence is obtained from a comparison of the diurnal variation on Mt. Norikura (2 770 m, 11.4 GeV) to that in Itabashi (20 m, 11.5 GeV). According to theoretical calculations based on a one-way solar anisotropy, the time of maximum at high altitude is earlier than or equal to that at sea level, but observations obtained during Dec. 1966 to Mar. 1967 suggest that the opposite is true.

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Decadal trends in the diurnal variation of galactic cosmic rays observed using neutron monitor data

Annales Geophysicae ◽

10.5194/angeo-35-825-2017 ◽

2017 ◽

Vol 35 (4) ◽

pp. 825-838 ◽

Cited By ~ 2

Author(s):

Simon Thomas ◽

Mathew Owens ◽

Mike Lockwood ◽

Chris Owen

Keyword(s):

Phase Change ◽

Diurnal Variation ◽

Neutron Monitor ◽

Cosmic Ray ◽

Galactic Cosmic Rays ◽

Energetic Particles ◽

Magnetic Polarity ◽

Neutron Monitors ◽

Neutron Monitor Data ◽

Monitor Data

Abstract. The diurnal variation (DV) in galactic cosmic ray (GCR) flux is a widely observed phenomenon in neutron monitor data. The background variation considered primarily in this study is due to the balance between the convection of energetic particles away from the Sun and the inward diffusion of energetic particles along magnetic field lines. However, there are also times of enhanced DV following geomagnetic disturbances caused by coronal mass ejections or corotating interaction regions. In this study we investigate changes in the DV over four solar cycles using ground-based neutron monitors at different magnetic latitudes and longitudes at Earth. We divide all of the hourly neutron monitor data into magnetic polarity cycles to investigate cycle-to-cycle variations in the phase and amplitude of the DV. The results show, in general, a similarity between each of the A < 0 cycles and A > 0 cycles, but with a phase change between the two. To investigate this further, we split the neutron monitor data by solar magnetic polarity between times when the dominant polarity was either directed outward (positive) or inward (negative) at the northern solar pole. We find that the maxima and minima of the DV changes by, typically, 1–2 h between the two polarity states for all non-polar neutron monitors. This difference between cycles becomes even larger in amplitude and phase with the removal of periods with enhanced DV caused by solar wind transients. The time difference between polarity cycles is found to vary in a 22-year cycle for both the maximum and minimum times of the DV. The times of the maximum and minimum in the DV do not always vary in the same manner between A > 0 and A < 0 polarity cycles, suggesting a slight change in the anisotropy vector of GCRs arriving at Earth between polarity cycles. Polar neutron monitors show differences in phase between polarity cycles which have asymptotic directions at mid-to-high latitudes. All neutron monitors show changes in the amplitude of the DV with solar polarity, with the amplitude of the DV being a factor of 2 greater in A < 0 cycles than A > 0 cycles. In most cases the change in timing of the maximum /minimum is greatest with the stations' geomagnetic cut-off rigidity shows little variation in the DV phase with latitude. We conclude that the change in the DV with the dominant solar polar polarity is not as simple as a phase change, but rather an asymmetric variation which is sensitive to the neutron monitor's asymptotic viewing direction.

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Determination of the solar-flare cosmic-ray rigidity spectrum using the worldwide neutron monitor network

Canadian Journal of Physics ◽

10.1139/p70-057 ◽

1970 ◽

Vol 48 (4) ◽

pp. 419-431 ◽

Cited By ~ 6

Author(s):

R. A. R. Palmeira ◽

R. P. Bukata ◽

P. T. Gronstal

Keyword(s):

Cosmic Rays ◽

Solar Flare ◽

Neutron Monitor ◽

Cosmic Ray ◽

Spectral Exponent ◽

The Earth ◽

Rigidity Spectrum

The determination of the rigidity spectrum of solar-flare-produced cosmic rays is examined. A method based on the ratio of relative enhancements observed at two stations sufficiently separated in latitude is discussed, and graphs are presented showing the expected ratio of enhancements as a function of the spectral exponent of the flare-produced cosmic rays for 6 pairs of stations. This method, which assumes that the cosmic-ray particles arrive at the earth isotropically, is then applied to the 28 January 1967 event during which this condition of isotropy is shown to exist. An extension of this method to the case of anisotropic arrival of solar cosmic-ray particles using the concept of variational coefficient is outlined.

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Two anisotropies of the cosmic-ray particles producing the cosmic-ray diurnal variation

Canadian Journal of Physics ◽

10.1139/p68-361 ◽

1968 ◽

Vol 46 (10) ◽

pp. S828-S830

Author(s):

Masatoshi Kitamura

Keyword(s):

Cosmic Rays ◽

Diurnal Variation ◽

Interplanetary Space ◽

Geomagnetic Latitude ◽

Cosmic Ray ◽

Diurnal Variations ◽

Low Energy ◽

The Other ◽

Energy Spectra ◽

Cosmic Ray Intensity

The solar diurnal variations of both meson and nucleon components of cosmic rays at sea level at geomagnetic latitude 57.5° and geomagnetic longitude 0° are analyzed by the model in which two anisotropies of cosmic-ray particles (one of them, Δj1, from about 20 h L.T. and the other, Δj2, from about 8 h L.T. in interplanetary space) produce the solar diurnal variation of the cosmic-ray intensity on the earth.When the energy spectra of Δj1 and Δj2 are represented by [Formula: see text] and [Formula: see text], respectively, where j0(E) is the normal energy spectrum of the primary cosmic rays, it is shown that the evaluation for m1 = 1, 2, m2 = 0 and the cutoffs at 8 and 10 BeV on the low-energy side of spectra of both Δj1 and Δj2 agree well with the observational results at Deep River.

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