Flux calculation
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Use this calculator to determine the relative neutron flux at a particular location. The output value is relative to the sea-level flux in New York City, New York, USA. This point has historically been the reference point for neutron flux measurements.

Instructions for use are here (opens a new window) and summarized at the bottom of this page.

Elevation, Pressure or Depth - Enter a single value and check the appropriate box
Station pressure
Atmospheric depth g/cm 2
Solar Modulation
Solar modulation % (0 is minimum flux / active sun,
100 is maximum flux / quiet sun)
Relative flux (NYC, NY, USA = 1.00)
The following parameters refer to values calculated in Annex A of JESD89A
Station pressure
Atmospheric depth g/cm 2
Fa parameter (NYC, NY, USA = 1.00)
Fb parameter (NYC, NY, USA = 1.00)
Rigidity cutoff (NYC, NY, USA = 2.08)

Last modified: 01/16/2019 11:06:17

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Enter latitude and longitude for the location of interest.  Enter either the elevation, barometric station pressure or the atmospheric depth of the location. Pressing Submit will validate the entered values and output the relative flux. 

NOTE: The "Station Pressure" is the mean, uncorrected barometer reading for the location. Values from the National Weather Service are generally corrected back to their equivalent value at sea-level and are unsuitable for this calculation.

Values of geomagnetic vertical cutoff rigidity used to calculate the relative neutron flux were provided by the Aerospace Medical Research Division of the Federal Aviation Administration's Civil Aerospace Medical Institute. The cutoff data were generated by M.A. Shea and D.F. Smart using the International Geomagnetic Reference Field for 1995.

Downloading or other commercial use of this cutoff data without written consent of the FAA is prohibited.


M. S. Gordon, P. Goldhagen, K. P. Rodbell, T. H. Zabel, H. H. K. Tang, J. M. Clem, and P. Bailey, "Measurement of the Flux and Energy Spectrum of Cosmic- Ray Induced Neutrons on the Ground," IEEE Transactions on Nuclear Science, vol. 51, no. 6, pp. 3427-3434, Dec. 2004.

J. Clem and L. Dorman, "Neutron monitor response functions," Space Sci. Rev., vol. 93, no. 1-2, pp. 335-363, 2000, and references therein.

A. Belov, A. Struminsky, and V. Yanke, "Neutron Monitor Response Functions for Galactic and Solar Cosmic Rays", 1999 ISSI Workshop on Cosmic Rays and Earth, poster presentation and personal communication, 1999.

M. A. Shea and D. F. Smart, "The Influence of the Changing Geomagnetic Field on Cosmic Ray Measurements," J. Geomag. Geoelectr., 62, 1107-1121, (1990).

M. E. Shea and D. F. Smart, "Tables of asymptotic directions and vertical cutoff rigidities for a five degree by fifteen degree world grid as calculated using the International Geomagnetic Reference Field for epoch 1975.0," Air Force Geophysics Laboratory, Report AFCRL-TR-75-0185, Hanscom AFB, Massachusetts, 1975. (AD-A012509)


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Last modified: September 15, 2006