DROPOUT OF DIRECTIONAL ELECTRON INTENSITIES IN LARGE SOLAR ENERGETIC PARTICLE EVENTS

ABSTRACT In the "gradual" solar energetic particle (SEP) event during solar cycle 23 we have observed the dispersionless modulation ("dropout") in directional intensities of nonrelativistic electrons. The average duration of dropout periods is ∼0.8 hr, which is consistent with th...

Full description

Saved in:
Bibliographic Details
Published in:The Astrophysical journal 2016-01, Vol.816 (2), p.1-21, Article 93
Main Authors: Tan, Lun C., Reames, Donald V.
Format: Article
Language:English
Subjects:
ANISOTROPY
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
COMPUTERIZED SIMULATION
CORRELATIONS
Dropouts
Fluid dynamics
Fluid flow
HELIOSPHERE
IONS
MAGNETIC FIELDS
MAGNETIC FLUX
RESONANCE SCATTERING
Slabs
SOLAR CYCLE
SOLAR ELECTRONS
SOLAR WIND
SUN
Sun: heliosphere
Sun: magnetic fields
Sun: particle emission
TURBULENCE
Turbulent flow
waves
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:ABSTRACT In the "gradual" solar energetic particle (SEP) event during solar cycle 23 we have observed the dispersionless modulation ("dropout") in directional intensities of nonrelativistic electrons. The average duration of dropout periods is ∼0.8 hr, which is consistent with the correlation scale of solar wind turbulence. During the dropout period electrons could display scatter-free transport in an intermittent way. Also, we have observed a decrease in the anisotropic index of incident electrons with increasing electron energy (Ee), while the index of scattered/reflected electrons is nearly independent of Ee. We hence perform an observational examination of the correlation between the anisotropic index of low-energy scattered/reflected electrons and the signature of the locally measured solar wind turbulence in the dissipation range, which is responsible for resonant scattering of nonrelativistic electrons. Since during the dropout period the slab turbulence fraction is dominant (0.8 0.1), we pay close attention to the effect of slab fraction on the correlation examined. Our observation is consistent with the simulation result that in the dominance of the slab turbulence component there should exist a dispatched structure of magnetic flux tubes, along which electrons could be transported in a scatter-free manner. Since a similar phenomenon is exhibited in the "impulsive" SEP event, electron dropout should be a transport effect. Therefore, being different from most ion dropout events, which are due to a compact flare source, the dropout of directional electron intensities should be caused by the change of turbulence status in the solar wind.
ISSN:0004-637X
1538-4357
DOI:10.3847/0004-637X/816/2/93