Time and other Variations in the Intensity of Cosmic Ray Neutrons

AbstractWe have measured the barometer coefficient of cosmic ray neutron production at sea level and find the value -9,25% ± 0,20/cmHg. We have shown that there is no diurnal variation of neutron production of amplitude greater than about 0,4 %. The effects of the large solar flare of November 19 th , 1949 on cosmic ray neutrons were much greater than on ionising cosmic rays at sea level; the maximum factor of increase was more than 5 and the intensity remained measurably above normal for about 12 hours. A small increase of neutron intensity is found, statistically, to be correlated with a number of recorded radio fade-outs. It is suggested that neutron measurements are particularly suitable for studying temporal variations of cosmic rays. The latitude increase of cosmic ray neutrons between geomagnetic latitude 54,5° and 56,5° was found to be about 2%. No certain increase was found between 56,5° and 59,5°.

Download Full-text

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.

Download Full-text

Neutron production by cosmic-ray particles at sea level and underground

Il Nuovo Cimento ◽

10.1007/bf02786101 ◽

1951 ◽

Vol 8 (5) ◽

pp. 326-340 ◽

Cited By ~ 11

Author(s):

R. D. Sard ◽

M. F. Crouch ◽

D. R. Jones ◽

A. M. Conforto ◽

B. F. Stearns

Keyword(s):

Sea Level ◽

Cosmic Ray ◽

Neutron Production

Download Full-text

A reevaluation of the atmospheric pressure dependence of secondary cosmic-ray neutrons in the context of Cosmic-Ray Neutron Sensing

10.5194/egusphere-egu21-10602 ◽

2021 ◽

Author(s):

Jannis Weimar ◽

Paul Schattan ◽

Martin Schrön ◽

Markus Köhli ◽

Rebecca Gugerli ◽

...

Keyword(s):

Cosmic Rays ◽

Hydrogen Content ◽

Atmospheric Pressure ◽

Cosmic Ray ◽

Galactic Cosmic Rays ◽

Atmospheric Air ◽

Neutron Intensity ◽

The Earth ◽

Wide Range ◽

Primary Cosmic Rays

Secondary cosmic-ray neutrons may be effectively used as a proxy for environmental hydrogen content at the hectare scale. These neutrons are generated mostly in the upper layers of the atmosphere within particle showers induced by galactic cosmic rays and other secondary particles. Below 15 km altitude their intensity declines as primary cosmic rays become less abundant and the generated neutrons are attenuated by the atmospheric air. At the earth surface, the intensity of secondary cosmic-ray neutrons heavily depends on their attenuation within the atmosphere, i.e. the amount of air the neutrons and their precursors pass through. Local atmospheric pressure measurements present an effective means to account for the varying neutron attenuation potential of the atmospheric air column above the neutron sensor. Pressure variations possess the second largest impact on the above-ground epithermal neutron intensity. Thus, using epithermal neutrons to infer environmental hydrogen content requires precise knowledge on how to correct for atmospheric pressure changes.We conducted several short-term field experiments in saturated environments and at different altitudes, i.e. different pressure states to observe the neutron intensity pressure relation over a wide range of pressure values. Moreover, we used long-term measurements above glaciers in order to monitor the local dependence of neutron intensities and pressure in a pressure range typically found in Cosmic-Ray Neutron Sensing. The results are presented along with a broad Monte Carlo simulation campaign using MCNP 6. In these simulations, primary cosmic rays are released above the earth atmosphere at different cut-off rigidities capturing the whole evolution of cosmic-ray neutrons from generation to attenuation and annihilation. The simulated and experimentally derived pressure relation of cosmic-ray neutrons is compared to those of similar studies and assessed in the light of an appropriate atmospheric pressure correction for Cosmic-Ray Neutron Sensing.

Download Full-text

Geomagnetic activity and diurnal variation of cosmic ray neutron intensity

Proceedings of the Indian Academy of Sciences - Section A ◽

10.1007/bf03047467 ◽

1965 ◽

Vol 62 (3) ◽

pp. 139-144

Author(s):

D. S. R. Murty ◽

Y. Nagabhushanam ◽

K. Ramanuja Rao

Keyword(s):

Diurnal Variation ◽

Geomagnetic Activity ◽

Cosmic Ray ◽

Neutron Intensity

Download Full-text

A Cloud-Chamber Study of Neutron Production by Sea-Level Cosmic Rays with Particular Reference toμ-Mesons Stopped in Lead

Physical Review ◽

10.1103/physrev.91.373 ◽

1953 ◽

Vol 91 (2) ◽

pp. 373-384 ◽

Cited By ~ 6

Author(s):

E. J. Althaus ◽

R. D. Sard

Keyword(s):

Cosmic Rays ◽

Sea Level ◽

Neutron Production ◽

Cloud Chamber ◽

Chamber Study

Download Full-text

The North–South Anisotropy and the Radial Density Gradient of Galactic Cosmic Rays at 1 AU

Publications of the Astronomical Society of Australia ◽

10.1017/s1323358000020191 ◽

1995 ◽

Vol 12 (2) ◽

pp. 153-158 ◽

Cited By ~ 1

Author(s):

D. L. Hall ◽

M. L. Duldig ◽

J. E. Humble

Keyword(s):

Cosmic Rays ◽

Diurnal Variation ◽

Density Gradient ◽

Cosmic Ray ◽

Ecliptic Plane ◽

Galactic Cosmic Rays ◽

Radial Density ◽

Sidereal Time ◽

Direction Parallel ◽

The North

AbstractThe radial density gradient (Gr) of Galactic cosmic rays in the ecliptic plane points outward from the Sun. This indicates an increasing density of cosmic ray particles beyond the Earth’s orbit. Due to this gradient and the direction of the Sun’s interplanetary magnetic field (IMF) above and below the IMF wavy neutral sheet, there exists an anisotropic flow of cosmic ray particles approximately perpendicular to the ecliptic plane (i.e. in the direction parallel to BIMF × Gr). This effect is called the north–south anisotropy (ξNS) and manifests as a diurnal variation in sidereal time in the particle intensity recorded by a cosmic ray detector. By analysing the yearly averaged sidereal diurnal variation recorded by five neutron monitors and six muon telescopes from 1957 to 1990, we have deduced probable values of the average rigidity spectrum and magnitude of ξNS. Furthermore, we have used determined yearly amplitudes of ξNS to infer the magnitude of Gr for particles with rigidities in excess of 10 GV.

Download Full-text