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Measurement of the Low-Energy Portion of the Primary Cosmic Ray Spectrum

Entry ID: gov.noaa.ngdc.G00599

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Summary

Abstract: ABSTRACT: Most cosmic rays come from the galaxy, though some are produced by eruptive events on the Sun's surface. These high energy cosmic ray particles can affect satellites, causing single event upsets. Scientists have postulated that cosmic rays can affect the earth by causing changes in weather. Cosmic rays can cause clouds to form in the upper atmosphere, after the particles collide with ... other atmospheric particles in our troposphere. The process of a cosmic ray particle colliding with particles in our atmosphere and disintegrating into smaller pions, muons, and the like, is called a cosmic ray shower. These particles can be measured on the Earth's surface by neutron monitors.Ground-based neutron monitors detect variations in the approximately 500 Mev to 20 GeV (low energy) portion of the primary cosmic ray spectrum. This class of cosmic ray detector is more sensitive in the approximate 500 Mev to 4 GeV portion of the cosmic ray spectrum than are cosmic ray muon detectors. The portion of the cosmic ray spectrum that reaches the Earth's atmosphere is controlled by the geomagnetic cutoff which varies from a minimum (theoretically zero) at the magnetic poles to a vertical cosmic ray cutoff of about 15 GV (ranging from 13 to 17) in the equatorial regions. (Note: GeV is a unit of energy, GV is a unit of magnetic rigidity). The primary cosmic ray particles interact with the atmosphere and generate secondaries, some of which will reach the surface of the Earth. In high latitude regions of the Earth, where the geomagnetic cutoff is low, the lower threshold response of the neutron monitor is controlled by the atmospheric mass (about 1030 grams at sea level) which limits the response threshold of the neutron monitor to primary radiation of about 430 MeV. (At the South Pole, where the surface is 2820 M above sea level, the reduced atmospheric mass lowers the primary radiation detection threshold to about 300 MeV). At mid-latitudes or equatorial latitudes, the detection threshold is controlled by the geomagnetic cutoff. Neutron monitors at high altitudes have higher counting rates than neutron monitors at lower altitudes because of the atmospheric absorption of the cosmic ray secondaries generated near the top of the atmosphere. When the secondary cosmic rays interact in the monitor, (actually in lead surrounding the counters) they cause nuclear disintegrations, or stars. These stars are composed of charged fragments and neutrons typically in the energy range of tens to hundreds of MeV, even up to GeV energies. As a result of these high energy nuclear interactions, there will be more secondary fragments generated than incident particles and hence there is a multiplier effect for the counters. The neutrons are moderated and then counted using Boron tri-fluoride (BF3) proportional counters which are efficient thermal neutron detectors; hence the name neutron monitor. The original design is often designated as an IGY neutron monitor. A description of this type of instrument is given by Simpson, (Annals of the IGY, Vol. 4, pp. 351-373, 1957). The NM-64 or super neutron monitor was developed for the IQSY (International Quiet Sun Years 1964-65) when instruments with a higher counting capacity were required. A description of this type of neutron monitor is given by Carmichael (Annals of the IQSY, Vol. 1, pp. 178-197, 1968). Super neutron monitors are often designated as xx-NM-64 where xx is the number of tubes in the monitors. An 18-NM-64 at high latitude has a counting rate of approximately 1 million counts per hour or 0.1 percent statistics. The neutron monitor and supermonitor digital data for the time period 1953 to present are available at http://spidr.ngdc.noaa.gov and consist of over 100 stations' hourly (UT) values of: (a) counting rates corrected for atmospheric pressure effects; (b) uncorrected counting rates; and (c) atmospheric pressure data. If it is not possible to have all three types of data, the most important is the counting rate corrected for atmospheric pressure.NGDC also holds paper archives for some cosmic ray Ionization Chamber monitors and some meson telescopes, mostly during the period of the International Geophysical Year (IGY) and International Quiet Sun Years (IQSY) 1957-1968.

CURRENTNESS REFERENCE: Ground Condition

DATA SET CREATORS: DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce (comp)

Purpose: PURPOSE: Cosmic Ray Research

Related URL

Link: GET DATA

Description: Get data

Geographic Coverage

(Click for Interactive Map)

Spatial coordinates

N: 90.0

S: -90.0

E: 180.0

W: -180.0

Data Set Citation

Dataset Originator/Creator: Please See Summary

Dataset Title: Measurement of the Low-Energy Portion of the Primary Cosmic Ray Spectrum

Dataset Series Name: Solar Terrestrial Physics

Dataset Release Date: 1953

Dataset Release Place: Boulder, CO

Dataset Publisher: National Geophysical Data Center

Version: First

Issue Identification: 'STP-93-3, Neutron Monitor Data on CD-ROM'

Online Resource: http://www.ngdc.noaa.gov/stp/SOLAR/COSMIC_RAYS/cosmic.html

Temporal Coverage

Start Date: 1953-01-01

Science Keywords

SUN-EARTH INTERACTIONS > SOLAR ENERGETIC PARTICLE PROPERTIES

ISO Topic Category

CLIMATOLOGY/METEOROLOGY/ATMOSPHERE

ENVIRONMENT

IMAGERY/BASE MAPS/EARTH COVER

OCEANS

Instrument

MODIS > Moderate-Resolution Imaging Spectroradiometer

SEAWIFS > Sea-Viewing Wide Field-of-View Sensor

Project

EOSDIS > Earth Observing System Data Information System

SEAWIFS > Sea-viewing Wide Field-of-view Sensor

Access Constraints SeaDAS is available for download via anonymous FTP from seadas.gsfc.nasa.gov. To connect to the SeaDAS ftp site and download the files, click here. The /seadas directory contains the following compressed tar files. The completed SeaDAS installation will require about 330MB without demo files and 950 MB with demo files. Using the embedded IDL runtime feature will add an additional 130MB to the installation.

Use Constraints SeaDAS is currently available for Linux Mac OS X (Intel and PowerPC), and also runs as a Vmware virtual appliance on Windows platforms. The SeaDAS source code is publicly available, and if any group is interested in porting SeaDAS to another platform, the development team will be happy to give any kind of assistance possible.

The Interactive Data Language (IDL) from ITT Visual ...

Service Provider

NASA/GSFC/SED/ESD/GCDC/OBPG > Ocean Biology Processing Group (OBPG), Global Change Data Center, Earth Sciences Division, Science and Exploration Directorate, Goddard Space Flight Center, NASA

Service Organization URL: http://oceancolor.gsfc.nasa.gov/

Service Provider Personnel
Name: GENE CARL FELDMAN Phone: (301) 286-9428 Fax: (301) 286-0268 Email: gene.c.feldman at nasa.gov Contact Address: Data System Manager NASA/Goddard Space Flight Center Mailstop 614.8 City: Greenbelt Province or State: MD Postal Code: 20771 Country: USA

Distribution

Distribution Media: FTP

Distribution Size: 950 MB

Fees: Free

Personnel

TYLER B. STEVENS

Role: SERF AUTHOR

Phone: (301) 614-6898

Fax: 301-614-5268

Email: Tyler.B.Stevens at nasa.gov

Contact Address:

NASA Goddard Space Flight Center

Global Change Master Directory

City: Greenbelt

Province or State: MD

Postal Code: 20771

Country: USA

Publications/References

Fu, G., Baith, K. S., and McClain, C. R., 1998, "SeaDAS: The SeaWiFS Data Analysis System", Proceedings of "The 4th Pacific Ocean Remote Sensing Conference", Qingdao, China, July 28-31, 1998, 73-79.

Creation and Review Dates

SERF Creation Date: 2002-11-09
SERF Last Revision Date: 2011-04-22

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