Cosmic Ray Neutron Monitor Data

This web page is under review

Descriptive text on cosmic rays.

Cosmic rays affect satellite electronics and ground-based computer systems at high altitudes -- see Terrestrial Cosmic Rays and Soft Errors, IBM experiments in soft fails in computer electronics, IBM Journal, Vol. 40, 1996. Engineers can find useful information about soft errors in electronics from cosmic rays on the Particle Interactions with Matter website. The high energy particles affect airplane passengers -- the FAA has an online cosmic ray airline flight profile calculation available. These effects are especially augmented during large solar particle events. During these times, polar flights are generally diverted to lower latitude flight paths.

1. Cosmic ray neutron monitor data -- daily and monthly averages from a worldwide network 1953-present ---- Download Data

COSMIC RAYS (from SGD Explanation of Data Reports)

Cosmic Ray Tabulated Observations -- The table presents the daily (UT) average counting rates per hour (scaled) for seven high counting rate neutron monitors: Thule, Deep River, Kiel, Climax, Beijing, Tokyo, and Haleakala. The characteristics of the stations are given below; the data are corrected applying the barometric coefficients to the listed standard station pressure.

The Climax, CO, USA, and Huancayo, Peru, (replaced by Haleakala, Hawaii) Neutron Monitor data are communicated by J.A. Simpson and G. Lentz of the Enrico Fermi Institute for Nuclear Studies, University of Chicago. The instruments are standard Chicago type neutron monitors, utilizing 12 BF3, counter tubes, divided into two identical and independent sections. For a more detailed description of the neutron intensity monitors see J.A. Simpson, Annals of the IGY, Vol. IV, Part VII, 351-373, 1957. The publication of these data in this monthly series began September 1960 for Climax and in January 1979 for Huancayo. Hourly averages, both corrected and uncorrected and local pressure data are available in both tabular and digital form for these stations from the WDC-A for Solar-Terrestrial Physics, Boulder, CO.

The Deep River, Ontario, Canada, neutron monitor, follows the IQSY design [IQSY Instruction Manual No. 7 which is published in the Annals of the IQSY, Vol 1, Chapter 13]. Publication of the daily rates in SGD began in January 1966 but a chart of hourly values from Deep River, described below, has been published in SGD since January 1959. Until December 31, 1972, the station was operated and maintained by Atomic Energy of Canada Ltd., but on January 1, 1973, the National Research Council of Canada took over the responsibility for maintenance of the station.

The 18-NM-64 neutron monitor located at Alert, Northwest Territories, Canada, was unique because its asymptotic cone of acceptance in space is less than 10 degrees wide and is aligned within 7 degrees of the spin axis of the Earth. Hence, unlike the stations whose cones of acceptance rotate with the Earth approximately in the plane of the ecliptic, Alert always "looks" into a fixed cone directed northward. It experiences negligible periodic diurnal intensity variation. The monitor at Alert was provided by Atomic Energy of Canada, Ltd., and housed in a building provided by National Research Council of Canada. It is the responsibility of the National Research Council; the day-to-day operation is by courtesy of the Canadian Meteorological Service. The data for Deep River and Alert are now provided by Margaret D. Wilson and M. Bercovitch of the National Research Council of Canada. The original data can be obtained from National Research Council of Canada, Ontario, Canada K1A OR6, or from any of the World Data Centers.

The Thule nucleonic intensity detector, of standard IQSY design, was originally located at the Geopole Station Greenland: latitude 76 degrees 36'N, longitude 68 degrees 48'W, altitude 260m, geomagnetic threshold rigidity essentially zero. At the end of 1976, it was moved to a new site on Thule Air Base. The coordinates are essentially unchanged except that the altitude is now close to sea level.

Data acquired after station relocation have been renormalized to be compatible with the earlier data. Thule data are communicated by John W. Bieber, Bartol Research Institute, University of Delaware, Newark, DE 19716 U.S.A. Thule data published in Solar Geophysical Data are preliminary. Final data are released to the World Data Centers and to the scientific community following an annual comprehensive review of instrument status and stability.

The Beijing superneutron monitor data are available from Prof. Du Heng, WDC-D Space Sciences, Center for Space and Applied Research, Beijing, China. The monitor was set up in 1983 and operated since early 1984. Its counting rate is 20 times as large as that of an IGY neutron monitor. Its statistical accuracy is 4.5 times as large as that of an IGY monitor. Data are exchanged routinely among the WDCs.

Two other monitors, at Kiel (18-NM-64) and Tokyo (36-NM-64), have asymptotic cones of acceptance much different from those given above. Therefore, they can be used to distinguish between UT-dependent and LT-dependent time variations. Higher cutoff rigidities also aid further estimation of rigidity dependence.

The publication in SGD of the Kiel and Tokyo data began with the December 1973 data. The data from both neutron monitors are routinely submitted to the World Data Centers A, B, and C2 for Cosmic Rays as well as to listed researchers. Kiel data have been available since September 1964 and Tokyo (or Tokyo-Itabashi) data since January 1970. Since there were changes in the number of counters, a revision of pressure reduction, and so on, the level of Tokyo data has changed several times. The Kiel data are communicated to Solar-Geophysical Data by K. Takahashi after receiving the Kiel data from K. Rohrs.

Charts -- Variations of cosmic ray intensity are depicted in chart form in SGD for the above stations. The vertical scale lines mark the days of the month in Universal Time. The horizontal scale lines are in intervals of 5% deviation from the arbitrarily chosen 100% reference level for each station. The 100% reference levels are based upon (after barometric correction) 0.6740x106 counts per hour for Deep River, and 0.7132x106 for Alert. For Thule, Kiel, Climax, and Tokyo, the plots represent percentage deviation from the mean intensity of the corresponding 27 days which is taken to be the 100% level.

Cosmic Ray Tabulated Observations -- The tables present the daily (UT) average counting rates per hour (scaled) for about seven high counting rate neutron monitors: Thule, Deep River, Kiel, Climax, Beijing, Tokyo, and Haleakala. The characteristics of the stations are given below; the data are corrected applying the barometric coefficients to the listed standard station pressure.

Cosmic Ray Neutron Monitors

Station Lat. North Long. East Cutoff GV* Alt. m Scaling Type Scaling Factor Baro. coeff. %/mm Hg Standard press. mm Hg
Thule 76.50 291.30 0.00 44 NM 64 100 0.99 754
Deep River 46.10 282.50 1.07 145 NM 64 300 0.987 747
Calgary 51.08 245.87 1.09 1128 NM 64 300 1.0155 671.1
Kiel 54.34 10.12 2.32 54 NM 64 100 0.961 755
Climax 39.37 253.82 2.97 3400 IGY 100 0.962 504
Beijing 40.08 116.26 9.56 47 NM 64 256 0.75%/mb 624.8
Tokyo 35.75 139.72 11.50 20 NM 64 256 0.888 760.5
Haleakala 20.71 203.07 13.30 3052 NM 64 1000 0.962 518

Calculated by DGRF75 (COSMIC RAY TABLE No.1, ed. WDC-C2 Japan, March 1983).

Hourly data for many stations are available in the Space Physics Interactive Data Resource (SPIDR) database management system -- an inventory of the data is available.

2. Cosmic Ray Forbush Decreases (FDs) from Mt. Washington Observatory 1955-1995 data -- (N44.30 E288.70; Cut-off Rigidity = 1.24 GV; Altitude 1900 m) -- Forbush decreases are abrupt decreases of the background galactic cosmic ray intensity as observed by neutron monitors. They are associated with major plasma and magnetic field enhancements in the solar wind at or beyond the earth. These magnetic field enhancements deflect the background cosmic ray particles. The phenomenon is named after Scott Forbush who studied them extensively.

3. Cosmic Ray Ground Level Enhancements (GLEs) 1942-2001 -- M.A. Shea and D.F. Smart -- GLEs are sharp increases in the gound-level cosmic ray count to at least 10 percent above background, associated with solar protons of energies greater than 500 MeV. GLEs are relatively rare, occurring only a few times each solar cycle. When they occur, GLEs begin a few minutes after flare maximum and last for a few tens of minutes to hours. Intense particle fluxes at lower energies can be expected to follow this initial burst of relativistic particles. GLEs are detected by neutron monitors, e.g., the monitor at Thule, Greenland.
  • List of GLEs -- includes the event number (1 to 65), event date, and some information about the baseline data used to determine the magnitude of the event.

4. Annals of the IGY Data -- ANNALS OF THE INTERNATIONAL GEOPHYSICAL YEAR (IGY) Volumes XXVI, XXVII and XXVIII (26, 27, and 28), Editor J.A. Simpson, CSAGI Reporter for Cosmic Rays

NOTE: These cosmic ray data are published in three volumes of the Annals of the IGY. Data were stored on 5 1/4 inch floppy diskettes and converted in 2005 to more recent storage media. Originally they were stored on punched cards. Not all station data published in the Annals have been found.

These bihourly cosmic ray databases include Neutron Monitor (46 stations), Cubical Telescope (38 stations), Vertical Telescope (2 stations), Ion Chamber (16 stations), Underground Telescope and Shower Apparatus (1 station) data monitored during the July 1957-December 1959 IGY and International Geophysical Cooperation (IGC) time period.