Abstract(draft). The HISCALE
instrument on Ulysses has been able to study the
anisotropy of the electron intensity in the
energy region ~40 keV to ~300 keV; this energy
is well away from the regime where solar wind
convection effects could be important. We find
the largest anisotropies during the south and
north polar passes, where they occasionally
exceed a factor of three in the 2-day averages
at the lowest energy. These are most pronounced
in the lowest energy channels in foreward and
backward facing HISCALE telescopes (WART-B and
LEFS 150) during the high latitude polar passes
in 1994 and 1995. There is a marked asymmetry
beween the south and north polar passes. In the
south, the period of high anisotropy in the LEFS
150 detector lasted only around 4 months,
whereas in the north the electron intensity did
not return to isotropy (±3%) until early 1997,
which is a period of ~20 months. We have
correlated the anisotropy with the direction of
the interplanetary magnetic field, and we find
that over the poles electrons at small pitch
angles are depleted. This is unlikely to be a
loss-cone effect, as the solid angle for loss
into the corona is very small. However, it could
be the result of adiabatic energy loss.
Implications of these results for the
acceleration and transport of electrons
throughout the heliosphere, and the ingress of
galactic cosmic ray electrons, are discussed.
Abstract(draft). Low energy
(~>50 keV) charged particles measured by the
HISCALE instrument on the Ulysses spacecraft
provided unique information on the particle
composition and intensity in both polar regions
of the Sun. Further, the rapid 160 deg.
South-to-North solar transit of Ulysses in early
1995 yielded new information on heliospheric
structure. This paper reviews several of the key
HISCALE results, including the latitude
dependence of particle acceleration by
corotating interaction regions, particle
propagation from equatorial regions of the Sun
to high heliolatitudes, and the appearance of
numerous periodic components in the power specra
of the particle variations, the frequencies of
which are consistent with those estimated (but
not as yet confirmed) for gravity-mode
oscillations of the Sun.
M. Boufaida,Gradients
of 0.3 to 5 MeV Protons in the 1-5 AU In-Ecliptic Plane:
Propagation, Modulation and Acceleration, Ph.D.
dissertation, Univ. of Kansas, 1995.
Abstract. Low energy charged particles with
energies ranging from 0.3 to 2 MeV are nearly
always present in the environment of the Earth.
Specific solar flare events and interplanetary
shock waves are identified as producing or
enhancing these fluxes. However, interplanetary
particles are observed even in the absence of
solar flares. The explanation of the presence of
these proton fluxes in the interplanetary medium
and accounting for their variations is a major
problem in space physics.
Observations of interplanetary proton fluxes have been made
continuously at 1 AU with IMP 8 from 1973 to the
present and in the 1-5 AU range by Voyager 1 and
2 (1977-78) and Ulysses (1990-91).
Daily-averaged proton fluxes of IMP 8, Voyager 1
and 2, and Ulysses have been carefully
interpolated to matching energy passbands so
that fluxes in the same passbands at two radial
distances could be compared. These
daily-averaged fluxes were then compared as
ratios, autocorrelation, cross correlation as
functions of time delay. The radial gradient,
the energy spectra and the distribution of these
proton fluxes were also examined.
The results showed that protons in the 0.3 to 5 MeV energy range
using the Voyager 1/IMP 8, Voyager 2/IMP 8, and
Ulysses/IMP 8 paired observations in the 1 to 5
AU in-ecliptic region tend to "decorrelate"
within increasing radial separation and become
uncorrelated by about 4 or 5 AU. Higher energy
fluxes decorrelate less rapidly, and lower
energy proton fluxes have smaller radial
gradients than higher energy. The radial
gradient of 0.3 to 0.5 MeV proton fluxes is
dominantly positive for 1-5 AU, whereas the
radial gradient of 2 to 4 MeV proton fluxes is
negative. We conclude that 0.3 to 0.5 MeV
protons are much more subject to interplanetary
acceleration than 2 to 5 MeV protons. The
results also showed that radial gradients are
robust and persist even if all heliolongitude
coherence is purposely removed by shuffling the
time order.
Our interpretation of this is that modulation of particle fluxes
and spectra are dominated by interplanetary
acceleration. Interplanetary shocks are the most
likely agents to produce this acceleration. We
suspect that "SDA" (Shock Drift Acceleration) is
more effective here than diffusive shock
acceleration because of the IMF (Interplanetary
Magnetic Field) geometry producing the high
shock normal angle for which "SDA" is most
efficient. This interplanetary process or "SDA"
maintains and redistributes the intensities of
0.3 to 1 MeV protons, whereas most of the
intensities of higher energy protons (>1 MeV)
are unaffected by this mechanism and originate
within 1 AU (as would be due to solar flares).
Abstract(draft). We describe an
electron event associated with a type III burst
observed by Ulysses. This event was observed
when the spacecraft crossed the region of strong
compression between a fast and a slow solar wind
stream, characterized by a relatively high
density and a complex behavior of the plasma
density, magnetic field and energetic electron
anisotropy. There is a clear influence of the
local plasma frequency on the time profiles of
the type III burst, even at frequencies
significantly higher than the average local
plasma frequency, which can be interpreted as
due to the reflection of the electromagnetic
radiation by randomly distributed regions of
high density.