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Title: Electron–Ion Intensity Dropouts in Gradual Solar Energetic Particle Events during Solar Cycle 23

Abstract

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.

Authors:
 [1]
  1. Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)
Publication Date:
OSTI Identifier:
22663193
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 846; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CORRELATIONS; DISTRIBUTION; ELECTRONS; EMISSION; HELIOSPHERE; IONS; MAGNETIC FIELDS; SIMULATION; SOLAR CYCLE; SOLAR PARTICLES; SOLAR WIND; TURBULENCE

Citation Formats

Tan, Lun C., E-mail: ltan@umd.edu. Electron–Ion Intensity Dropouts in Gradual Solar Energetic Particle Events during Solar Cycle 23. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA81D1.
Tan, Lun C., E-mail: ltan@umd.edu. Electron–Ion Intensity Dropouts in Gradual Solar Energetic Particle Events during Solar Cycle 23. United States. doi:10.3847/1538-4357/AA81D1.
Tan, Lun C., E-mail: ltan@umd.edu. Fri . "Electron–Ion Intensity Dropouts in Gradual Solar Energetic Particle Events during Solar Cycle 23". United States. doi:10.3847/1538-4357/AA81D1.
@article{osti_22663193,
title = {Electron–Ion Intensity Dropouts in Gradual Solar Energetic Particle Events during Solar Cycle 23},
author = {Tan, Lun C., E-mail: ltan@umd.edu},
abstractNote = {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.},
doi = {10.3847/1538-4357/AA81D1},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 846,
place = {United States},
year = {2017},
month = {9}
}