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ACE Solar Isotope Spectrometer (SIS) Daily Average Cosmic Ray Fluxes, HDF


Availability: At NSSDC, Ready for Offline Distribution (or Staging if Digital)

Time span: 1997-08-14 to 2001-03-28


This data collection contains daily Level 2 data in binary Hierarchical Data Format (HDF) format from the Solar Isotope Spectrometer (SIS) instrument on the Advanced Composition Explorer (ACE) spacecraft. This data set includes all measurements from solar quiet and active periods. Each data file covers one 27-day Bartels interval of solar rotation. Data records contain daily time averages of fluxes in units of particles/(cm^2*sr*sec*Mev/nucleon) in eight energy bands within the overall range of ~ 3 to 170 MeV/nucleon for the following elements: He, C, N, O, Ne, Mg, Si, S, and Fe. Isotopic data are not included. Energy bands for each element are different and are listed in the text file sis_energy_bands.txt. SIS counts for He may be low during periods of high solar activity and of consequently reduced livetimes for He. A data value of -999.9 indicates bad or missing data for the given time period. The number of counts is also given from which the statistical uncertainties can be calculated. Statistical flux uncertainties are computed from flux/sqrt(N), where N is the number of counts or events during the averaging period. The SIS team currently recommends adding an additional 5% to the statistical uncertainties computed from the counts data for other instrumental effects. Current release notes on Level 2 processing are given in the text file sis_release_notes.txt.

This collection is available on-line at:

Alternate Names

  • SIS Level-2 Daily Fluxes, HDF


  • Space Physics: Heliospheric Studies


  • 97-045A-05E

Additional Information



Questions and comments about this data collection can be directed to: Dr. John F. Cooper



NameRoleOriginal AffiliationE-mail
Dr. Andrew J. DavisGeneral ContactCalifornia Institute of
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