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Persistent URL http://purl.org/net/epubs/work/51735
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Record Id 51735
Title Cross-field gradients : general concept, importance of multi-spacecraft measurements and study at 1 AU of the source intensity gradient for E>30 keV solar event electrons
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Abstract Three main physical processes (and associated properties) are currently used to describe the flux and anisotropy time profiles of solar energetic particle events, called SEP profiles. They are (1) the particle scattering (due to magnetic waves), (2) the particle focusing (due to the decrease of the amplitude of the nterplanetary magnetic field (IMF) with the radial distance to the Sun) and (3) the finite injection profile at the source. If their features change from one field line to another, i.e. if there is a cross IMF gradient (CFG), then the shape of the SEP profiles will depend, at onset time, on the relative position of the spacecraft to the IMF and might vary significantly on small distance scale (e.g. 106km). One type of CFG is studied in this paper. It is called intensity CFG and considers variations, at the solar surface, only of the intensity of the event. It is shown here that drops of about two orders of magnitude over distances of ~104km at the Sun (1o of angular distance) can influence dramatically the SEP profiles at 1AU. This CFG can lead to either an under or overestimation of both the parallel mean free path and of the injection parameters by factor up to, at least, ~2-3 and 18, respectively. Multi-spacecraft analysis can be used to identify CFG. Three basic requirements have been proposed to identify, from the observation, the type of the CFG being measured.
Organisation CCLRC , SSTD , SSTD-SDD
Keywords Physics , Astronomy , Astrophysics , Coronal mass ejections , Energetic particles , Flares , Solar physics , Space plasma physics , Transport processes
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Language English (EN)
Type Details URI(s) Local file(s) Year
Journal Article Annales Geophysicae 18 (2000): 263-276. doi:10.1007/s00585-000-0263-z angeo-18-263-2000.pdf 2000
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