Electron-Ion Intensity Dropouts in Gradual Solar Energetic Particle Events during Solar Cycle 23

Since the field-line mixing model of Giacalone et al. suggests that ion dropouts cannot happen in the "gradual" solar energetic particle (SEP) event because of the large size of the particle source region in the event, the observational evidence of ion dropouts in the gradual SEP event sho...

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Bibliographic Details
Published in:The Astrophysical journal 2017-09, Vol.846 (1), p.18
Main Author: Tan, Lun C.
Format: Article
Language:English
Subjects:
Astrophysics
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
CORRELATIONS
DISTRIBUTION
Dropouts
ELECTRONS
EMISSION
Energetic particles
HELIOSPHERE
IONS
Longitude
MAGNETIC FIELDS
SIMULATION
Slopes
SOLAR CYCLE
SOLAR PARTICLES
SOLAR WIND
Solar wind turbulence
Sun: heliosphere
Sun: magnetic fields
Sun: particle emission
TURBULENCE
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Summary:Since the field-line mixing model of Giacalone et al. suggests that ion dropouts cannot happen in the "gradual" solar energetic particle (SEP) event because of the large size of the particle source region in the event, the observational evidence of ion dropouts in the gradual SEP event should challenge the model. We have searched for the presence of ion dropouts in the gradual SEP event during solar cycle 23. From 10 SEP events the synchronized occurrence of ion and electron dropouts is identified in 12 periods. Our main observational facts, including the mean width of electron-ion dropout periods being consistent with the solar wind correlation scale, during the dropout period the dominance of the slab turbulence component and the enhanced turbulence power parallel to the mean magnetic field, and the ion gyroradius dependence of the edge steepness in dropout periods, are all in support of the solar wind turbulence origin of dropout events. Also, our observation indicates that a wide longitude distribution of SEP events could be due to the increase of slab turbulence fraction with the increased longitude distance from the flare-associated active region.
ISSN:0004-637X
1538-4357
1538-4357
DOI:10.3847/1538-4357/aa81d1