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.
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 1.5x106km
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 cm2sr,
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.
