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Published 2001 | Published
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Are Solar Energetic Particles an Accelerated Sample of Solar Wind?


In the current picture of gradual solar energetic particle (SEP) events, the acceleration is believed to take place at a shock driven by a coronal mass ejection as it moves through the corona and out into the solar wind. It is often assumed that the solar wind provides the seed particles that are accelerated and later observed at 1 AU. We compare solar energetic particle and solar wind composition measurements, focusing on a comparison of the fractionation patterns with respect to first ionization potential. On the basis of several significant differences between the solar wind and SEP compositions, we conclude that most SEPs with energies >5 MeV/nucleon are not simply an accelerated sample of solar wind. Rather, SEPs and fast and slow solar wind appear to be distinct samples of coronal material with significantly different fractionation patterns. This implies that solar energetic particles must be accelerated within a few solar radii of the Sun.

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© Copernicus GmbH. This work was supported by NASA at the California Institute of Technology (under grant NAS5-6912), the Jet Propulsion Laboratory, and Goddard Space Flight Center.

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August 19, 2023
October 20, 2023