|
|
 |
|
|
Ann. Geophys., 21, 1383-1391, 2003
www.ann-geophys.net/21/1383/2003/
© European Geosciences Union 2003
From the Sun’s south to the north pole – Ulysses COSPIN/LET composition measurements at solar maximum
M. Y. Hofer, R. G. Marsden, T. R. Sanderson, and C. Tranquille
Research and Scientific Support Dept. of ESA, ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
Abstract. Based on elemental
abundance ratios derived from the Ulysses COSPIN/LET measurements, we
classified the energetic particle populations during and after the socalled
Fast Latitude Scan – the time period during which the Ulysses spacecraft
traveled from the highest heliolatitude south to maximum northern latitude,
i.e. 27 November 2000 to 13 October 2001 – as being mixed between solar
energetic particles (major component) and particles accelerated at stream
interaction regions. During the fast latitude scan, the Ulysses spacecraft made
the first transit in heliolatitude from pole to pole during solar activity
maximum conditions, providing a unique opportunity to acquire energetic
particle composition data over a maximum range of heliolatitudes in the inner
heliosphere. At low latitudes, based on our elemental abundance analysis, we
found that while solar energetic particles dominated, there were indications
for particle acceleration at single compression regions in a few instances. In
the high heliolatitude range the observed elemental particle compositions are
mainly of the solar energetic particle type. Within the statistical errors, the
observed abundance ratios were independent of latitude, and were characteristic
of solar energetic particles. These observations raise an important question
for the theories of particle propagation in the inner heliosphere. The daily
elemental abundance ratios of S/O, Mg/O and Si/O shown here are the first
measured ratios at high heliolatitudes in the energy range from 13.0 to 30.0
MeV/n.
Key words. Interplanetary physics
(energetic particles; interplanetary shocks) – Solar physics, astrophysics
and astronomy (flares and mass ejections)
Full Article in PDF (546 KB) |
|
|
