A FOCUSED TRANSPORT APPROACH TO THE TIMEDEPENDENT SHOCK ACCELERATION OF SOLAR ENERGETIC PARTICLES AT A FAST TRAVELING SHOCK
Abstract
Some of the most sophisticated models for solar energetic particle (SEP) acceleration at coronal mass ejection driven shocks are based on standard diffusive shock acceleration theory. However, this theory, which only applies when SEP pitchangle anisotropies are small, might have difficulty in describing firstorder Fermi acceleration or the shock preheating and injection of SEPs into firstorder Fermi acceleration accurately at lower SEP speeds where SEP pitchangle anisotropies upstream near the shock can be large. To avoid this problem, we use a timedependent focused transport model to reinvestigate firstorder Fermi acceleration at planar parallel and quasiparallel spherical traveling shocks between the Sun and Earth with high shock speeds associated with rare extreme gradual SEP events. The focused transport model is also used to investigate and compare three different shock preheating mechanisms associated with different aspects of the nonuniform crossshock solar wind flow, namely, the convergence of the flow (adiabatic compression), the shear tensor of the flow, and the acceleration of the flow, and a fourth shock preheating mechanism associated with the crossshock electric field, to determine which preheating mechanism contributes the most to injecting shock preheated source particles into the firstorder Fermi acceleration process. The effects of variations in traveling shockmore »
 Authors:
 Department of Physics, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)
 Publication Date:
 OSTI Identifier:
 22011755
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Astrophysical Journal; Journal Volume: 746; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANISOTROPY; ELECTRIC SHOCK; INCLINATION; MASS; SHOCK WAVES; SOLAR WIND; STEADYSTATE CONDITIONS; SUN; TIME DEPENDENCE; TRANSPORT THEORY
Citation Formats
Le Roux, J. A., and Webb, G. M. A FOCUSED TRANSPORT APPROACH TO THE TIMEDEPENDENT SHOCK ACCELERATION OF SOLAR ENERGETIC PARTICLES AT A FAST TRAVELING SHOCK. United States: N. p., 2012.
Web. doi:10.1088/0004637X/746/1/104.
Le Roux, J. A., & Webb, G. M. A FOCUSED TRANSPORT APPROACH TO THE TIMEDEPENDENT SHOCK ACCELERATION OF SOLAR ENERGETIC PARTICLES AT A FAST TRAVELING SHOCK. United States. doi:10.1088/0004637X/746/1/104.
Le Roux, J. A., and Webb, G. M. 2012.
"A FOCUSED TRANSPORT APPROACH TO THE TIMEDEPENDENT SHOCK ACCELERATION OF SOLAR ENERGETIC PARTICLES AT A FAST TRAVELING SHOCK". United States.
doi:10.1088/0004637X/746/1/104.
@article{osti_22011755,
title = {A FOCUSED TRANSPORT APPROACH TO THE TIMEDEPENDENT SHOCK ACCELERATION OF SOLAR ENERGETIC PARTICLES AT A FAST TRAVELING SHOCK},
author = {Le Roux, J. A. and Webb, G. M.},
abstractNote = {Some of the most sophisticated models for solar energetic particle (SEP) acceleration at coronal mass ejection driven shocks are based on standard diffusive shock acceleration theory. However, this theory, which only applies when SEP pitchangle anisotropies are small, might have difficulty in describing firstorder Fermi acceleration or the shock preheating and injection of SEPs into firstorder Fermi acceleration accurately at lower SEP speeds where SEP pitchangle anisotropies upstream near the shock can be large. To avoid this problem, we use a timedependent focused transport model to reinvestigate firstorder Fermi acceleration at planar parallel and quasiparallel spherical traveling shocks between the Sun and Earth with high shock speeds associated with rare extreme gradual SEP events. The focused transport model is also used to investigate and compare three different shock preheating mechanisms associated with different aspects of the nonuniform crossshock solar wind flow, namely, the convergence of the flow (adiabatic compression), the shear tensor of the flow, and the acceleration of the flow, and a fourth shock preheating mechanism associated with the crossshock electric field, to determine which preheating mechanism contributes the most to injecting shock preheated source particles into the firstorder Fermi acceleration process. The effects of variations in traveling shock conditions, such as increasing shock obliquity and shock slowdown, and variations in the SEP source with increasing shock distance from the Sun on the coupled processes of shock preheating, injection, and firstorder Fermi acceleration are analyzed. Besides the finding that the crossshock acceleration of the solar wind flow yields the dominant shock preheating mechanism at high shock speeds, we find that firstorder Fermi acceleration at fast traveling shocks differs in a number of respects from the predictions and assumptions of standard steadystate diffusive shock acceleration theory as is discussed below.},
doi = {10.1088/0004637X/746/1/104},
journal = {Astrophysical Journal},
number = 1,
volume = 746,
place = {United States},
year = 2012,
month = 2
}

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