The Acceleration of Energetic Particles at Coronal Shocks and Emergence of a Double Power-law Feature in Particle Energy Spectra
AffiliationUniv Arizona, Dept Planetary Sci
Keywordsacceleration of particles
Sun: coronal mass ejections (CMEs)
Sun: magnetic fields
Sun: particle emission
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationXiangliang Kong et al 2019 ApJ 883 49
RightsCopyright © 2019. The American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.
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AbstractWe present numerical modeling of particle acceleration at coronal shocks propagating through a streamer-like magnetic field by solving the Parker transport equation with spatial diffusion both along and across the magnetic field. We show that the location on the shock where the high-energy particle intensity is the largest, depends on the energy of the particles and on time. The acceleration of particles to more than 100 MeV mainly occurs in the shock-streamer interaction region, due to perpendicular shock geometry and the trapping effect of closed magnetic fields. A comparison of the particle spectra to that in a radial magnetic field shows that the intensity at 100 MeV (200 MeV) is enhanced by more than one order (two orders) of magnitude. This indicates that the streamer-like magnetic field can be an important factor in producing large solar energetic particle events. We also show that the energy spectrum integrated over the simulation domain consists of two different power laws. Further analysis suggests that it may be a mixture of two distinct populations accelerated in the streamer and open field regions, where the acceleration rate differs substantially. Our calculations also show that the particle spectra are affected considerably by a number of parameters, such as the streamer tilt angle, particle spatial diffusion coefficient, and shock compression ratio. While the low-energy spectra agree well with standard diffusive shock acceleration theory, the break energy ranges from similar to 1 MeV to similar to 90 MeV and the high-energy spectra can extend to similar to 1 GeV with a slope of similar to 2-3.
NoteOpen access article
VersionFinal published version
SponsorsNational Natural Science Foundation of ChinaNational Natural Science Foundation of China [11873036, 11503014, 11790303, 11790300]; Young Elite Scientists Sponsorship Program by China Association for Science and Technology; Young Scholars Program of Shandong University, Weihai; Specialized Research Fund for State Key Laboratories; National Science FoundationNational Science Foundation (NSF) ; U.S. Department of Energy, Office of Science, Office of Fusion Energy ScienceUnited States Department of Energy (DOE) [DE-SC0018240]; NSFNational Science Foundation (NSF) 
Except where otherwise noted, this item's license is described as Copyright © 2019. The American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.