Fundamental Technologies

ACE EPAM Pages

ACE EPAM Publications and Presentations Authored or Co-authored
by Fundamental Technologies Personnel

Publications

Patterson, J. D., MFSA background rates for ACE/EPAM and Ulysses/HISCALE, Fundamental Technologies in-house document, 2005.

Patterson, J. D., An analysis of solar energetic particle spectra throughout the inner heliosphere, Ph.D. dissertation, Univ. of Kansas, 2002.

Patterson, J. D., and T. P. Armstrong, Determination of HISCALE MFSA background rates using IMP-8 monitored omnidirectional galactic cosmic rays, Fundamental Technologies in-house document, 2001.

Gold, R. E., S. M. Krimigis, S. E. Hawkins III, D. K. Haggerty, D. A. Lohr, E. Fiore, T. P. Armstrong, G. Holland, and L. J. Lanzerotti, Electron, Proton, and Alpha Monitor on the Advanced Composition Explorer Spacecraft, Space Sci. Rev., 86, 541, 1998. Abstract, with link to full article.

Patterson, J. D., and T. P. Armstrong, Separation of proton and electron spectra for ACE/EPAM and Ulysses/HISCALE MFSA data, Fundamental Technologies in-house document.

AGU Abstracts

Armstrong, T. P., and G. G. Holland, Particle Acceleration at Interplanetary Shocks Observed with the Electron and Proton Anisotropy Monitor on the Advanced Composition Explorer, Spring AGU Meeting, May 1998, 1998 Spring Meeting Supplement to EOS, S262, 1998.

  Abstract (draft). The EPAM instrument observes energetic ions from 50 keV to 2 MeV in 32 energy channels and electrons from 50 keV up to about 400 keV in 14 channels with nearly full sky coverage at above 45 degrees of angular resolution. Observations made during a strong (B2/B1>3) forward shock that passed ACE at about 9:02 UT on Nov. 22 show a strong field aligned pre-shock anisotropy and a harder energy spectrum upstream than down. The shock spike enhancement occurred in all positive-ion species observed and extended to above several hundred keV. The event displays in strong fashion many of the attributes long known to occur when charged particles interact with propogating interplanetary shocks. There were small, fairly steady interplanetary charged particle fluxes before and after this event. We will attempt to establish the amount of energization that probably occurred to produce the intensity enhancement and to circumscribe the processes that might explain this energization.

Haggerty, D. K., R. Gold, S. M. Krimigis, S. E. Hawkins T. P. Armstrong, and G. G. Holland, Upstream Energetic Ion Events Observed by EPAM, Spring AGU Meeting, May 1998, 1998 Spring Meeting Supplement to EOS, S262, 1998.

  Abstract (draft). The EPAM instrument on the ACE mission measures protons, alpha particles, electrons and other ions through iron with energies from 46 keV to 5 MeV. EPAM has 5 apertures at various angles from the spacecraft spin axis that cover nearly the entire unit sphere. When combined with the magnetic field data on the same spacecraft, EPAM determines the full particle pitch angle distribution every 12 seconds. This report covers EPAM observations of over 100 energetic particle events, upstream from the earth’s bow shock in the first 100 days of the mission during the time the spacecraft moved from Earth to the L1 lagrange point, approximately 1.5x106 km upstream from earth toward the sun. Ion events from 47-580 keV, with very high anisotropies extending up to 2000:1 were observed. Detailed angular distributions show temporal effects during event onsets where over two minute delays were observed in ions of the same energy. Many events contain field-aligned, highly anisotropic ion fluxes with no electron contribution.

Krimigis, S. M., R. E. Gold, D. K. Haggerty, S. E. Hawkins II, T. P. Armstrong, and L. J. Lanzerotti, Early Results From the Electron, Proton and Alpha Monitor Instrument (EPAM) on the ACE Mission, Spring AGU Meeting, May 1998, 1998 Spring Meeting Supplement to EOS, S261, 1998.

  Abstract (draft). The EPAM instrument on the ACE mission measures ion and electron fluxes from ~50 keV to 5 MeV and ion composition from H to Fe with a time resolution of 1.5 s. The instrument covers the full unit sphere with 5 detector apertures at 30 deg., 60 deg., 120 deg. and 150 deg. from the spacecraft spin axis. With a total geometry factor of >2 cm2 sr, EPAM covers quiet time fluxes as well as large solar energetic particle events. It measures the full particle pitch angle distributions every 12 s. A spectrum accumulator circuit determines directional energy spectra at 32 logarithmically spaced energies every 128 s. The high time resolution and full sphere coverage are unique on ACE. EPAM was developed from the flight spare of the HI-SCALE instrument on Ulysses. The close similarity and intercalibration between EPAM and HI-SCALE provides an excellent basis for comparing particle environments at 1 AU with other regions of the heliosphere sampled by Ulysses. This report covers the period from launch out to orbit insertion into a halo about the L1 Lagrange point and the first 4 months of operation at L1. Spectra and composition are shown for a large solar energetic particle event in November, 1997. These are compared with quiet-times during the early orbit phase. During February and March, ACE and Ulysses were nearly radially aligned providing information about the propagation of energetic particles from 1 to 5 AU.

Gold, R. E., D. A. Lohr, D. K. Haggerty, S. M. Krimigis, T. P. Armstrong, and L. J. Lanzerotti, First Observations from the Electron, Proton, and Alpha Monitor (EPAM) on the ACE Spacecraft, Abstract SH52C-06, Fall AGU Meeting, December 1997, 1997 Fall Meeting Supplement to EOS, F562, 1997.

  Abstract (draft). The EPAM instrument on the Advanced Composition Explorer (ACE) measures the overall state of energetic particles between 50 keV and 5 MeV/nuc. With its full unit sphere coverage, atomic composition coverage from H to Fe, and dynamic range from low to very high flux levels, EPAM provides a monitor of the near-Earth interplanetary low energy particle populations. EPAM is also one of four instruments in the Real Time Solar Wind (RTSW) data stream that will provide 24 hour coverage of space weather phenomena of importance to telecommunications, electrical power transmission, and other technologies at Earth. EPAM was constructed from the flight spare of the HI-SCALE instrument on Ulysses; therefore, it is an excellent basis for comparisons of energetic particle populations in other regions of the heliosphere. This initial report of measurements from EPAM provides comparisons of low energy electrons (E > 50 keV) and ions (E > 50 keV), including composition data (E > 0.5 MeV/nuc), in the ecliptic as ACE approaches L1 with measurements presently being acquired by HI-SCALE at about 5 A.U. and 10 deg. heliographic latitude as Ulysses completes its first solar polar orbit.

For more EPAM publications, please visit the APL ACE EPAM website.

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Last modified March 8, 2011
T. Hunt-Ward
tizby@ftecs.com