Energetic Particle Observations and Propagation in the Three-dimensional Heliosphere During the 2006 December Events

We report observations of solar energetic particles obtained by the HI-SCALE and COSPIN/LET instruments onboard Ulysses during the period of isolated but intense solar activity in 2006 December, in the declining phase of the solar activity cycle. We present measurements of particle intensities and a...

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Bibliographic Details
Published in:The Astrophysical journal 2009-10, Vol.704 (1), p.469-476
Main Authors: Malandraki, O. E, Marsden, R. G, Lario, D, Tranquille, C, Heber, B, Mewaldt, R. A, Cohen, C. M. S, Lanzerotti, L. J, Forsyth, R. J, Elliott, H. A, Vogiatzis, I. I, Geranios, A
Format: Article
Language:English
Subjects:
ANISOTROPY
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
ATMOSPHERES
EMISSION
ENERGY RANGE
HELIOSPHERE
MAGNETIC FIELDS
MAIN SEQUENCE STARS
MASS
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SOLAR FLARES
SOLAR WIND
STARS
STELLAR ACTIVITY
STELLAR ATMOSPHERES
STELLAR FLARES
STELLAR WINDS
SUN
THREE-DIMENSIONAL CALCULATIONS
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Summary:We report observations of solar energetic particles obtained by the HI-SCALE and COSPIN/LET instruments onboard Ulysses during the period of isolated but intense solar activity in 2006 December, in the declining phase of the solar activity cycle. We present measurements of particle intensities and also discuss observations of particle anisotropies and composition in selected energy ranges. Active Region 10930 produced a series of major solar flares with the strongest one (X9.0) recorded on December 5 after it rotated into view on the solar east limb. Located over the South Pole of the Sun, at >72 deg S heliographic latitude and 2.8 AU radial distance, Ulysses provided unique measurements for assessing the nature of particle propagation to high latitudes under near-minimum solar activity conditions, in a relatively undisturbed heliosphere. The observations seem to exclude the possibility that magnetic field lines originating at low latitudes reached Ulysses, suggesting either that the energetic particles observed as large solar energetic particle (SEP) events over the South Pole of the Sun in 2006 December were released when propagating coronal waves reached high-latitude field lines connected to Ulysses, or underwent perpendicular diffusion. We also discuss comparisons with energetic particle data acquired by the STEREO and Advanced Composition Explorer in the ecliptic plane near 1 AU during this period.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/704/1/469