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ACE Electron, Proton, & Alpha Monitor (EPAM) 27-Day Particle Fluxes, ASCII


Availability: At NSSDC, Ready for Electronic Access

Time span: 1997-08-14 to 2001-04-24


This data collection contains Bartels solar rotation (27-day) Level 2 data in ASCII text format from the Electron, Proton, and Alpha Monitor (EPAM) instrument on the Advanced Composition Explorer (ACE) spacecraft. This data set includes all measurements from solar quiet and active periods. One data file covers the present time span of the data set for all 27-day intervals. Data records contain 27-day time averages of fluxes in units of particles/(cm2*sr*sec*Mev/nucleon). 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. Current release notes on Level 2 processing are given in the text file epam_release_notes.txt.

Data parameters are acquired by the six EPAM sensors, including the Deflected Electrons (DE) spectrometer for pure measurements of electrons above 40 keV, two Low Energy Foil Spectrometers (LEFS) for the flux and direction of electrons above 30 keV, two Low Energy Magnetic Spectrometers (LEMS) for the flux and direction of ions greater than 50 keV, and the Composition Aperture (CA) for elemental composition of H, He, CNO, and heavier (9 < Z <= 26) ions at MeV/nucleon energies. DE30 measures only electrons at 30 degrees to the spacecraft spin axis in four energy channels at 0.04 - 3.1 MeV. LEMS30 and LEMS120 provide ion measurements at 0.05 - 5 MeV in eight identical energy channels from with apertures offset at 30 and 120 degrees to the spacecraft spin axis. LEFS60 and LEFS150 measure electron fluxes in seven energy channels at 0.045 - 5 MeV with apertures at 60 and 150 degrees to the spin axis. After DOY 78, 1998, the E1, E2 and E3 channels (0.05 - 0.2 MeV) from LEFS150 contain fill data (-999.9). This is due to a sudden noise increase in the detector, which makes the output from these channels unreliable. CA60 measures ions at 60 degrees in two channels each for H at 0.5 - 1.2 MeV, He at 0.4 - 7 MeV/nucl., O at 5 - 19 MeV/nucl., and Fe at 0.2 - 0.8 MeV/nucl. The oxygen channels also include C and N, while 9 < Z < 26 ions also contribute to the iron channel, but O and Fe respectively dominate these CNO and Fe ion group channels. The H channels from CA60 are not presently included in this data set. Four integral flux channels (Z > 1, E > 0.7 MeV; Z > 7, E > 7.5 MeV; Z > 5, E > 2.5 MeV; Z > 10, E > 9.0 MeV) are provided for heavier ions by the WARTD60 component of CA60.

This collection is available on-line at:

Alternate Names

  • EPAM Level-2 27-Day Flux, ASCII


  • Space Physics: Heliospheric Studies


  • 97-045A-08F

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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