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Title: Structure of Energetic Particle Mediated Shocks Revisited

Abstract

The structure of collisionless shock waves is often modified by the presence of energetic particles that are not equilibrated with the thermal plasma (such as pickup ions [PUIs] and solar energetic particles [SEPs]). This is relevant to the inner and outer heliosphere and the Very Local Interstellar Medium (VLISM), where observations of shock waves (e.g., in the inner heliosphere) show that both the magnetic field and thermal gas pressure are less than the energetic particle component pressures. Voyager 2 observations revealed that the heliospheric termination shock (HTS) is very broad and mediated by energetic particles. PUIs and SEPs contribute both a collisionless heat flux and a higher-order viscosity. We show that the incorporation of both effects can completely determine the structure of collisionless shocks mediated by energetic ions. Since the reduced form of the PUI-mediated plasma model is structurally identical to the classical cosmic ray two-fluid model, we note that the presence of viscosity, at least formally, eliminates the need for a gas sub-shock in the classical two-fluid model, including in that regime where three are possible. By considering parameters upstream of the HTS, we show that the thermal gas remains relatively cold and the shock is mediated by PUIs.more » We determine the structure of the weak interstellar shock observed by Voyager 1 . We consider the inclusion of the thermal heat flux and viscosity to address the most general form of an energetic particle-thermal plasma two-fluid model.« less

Authors:
;  [1];  [2]
  1. Department of Space Science, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)
  2. Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States)
Publication Date:
OSTI Identifier:
22663598
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 841; 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; ACCELERATION; COMPUTERIZED SIMULATION; COSMIC RADIATION; FLUIDS; HEAT FLUX; HELIOSPHERE; HYDRODYNAMICS; MAGNETIC FIELDS; PLASMA; SHOCK WAVES; SOLAR WIND; TAIL IONS; VISCOSITY; VOYAGER SPACE PROBES

Citation Formats

Mostafavi, P., Zank, G. P., and Webb, G. M. Structure of Energetic Particle Mediated Shocks Revisited. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA6F10.
Mostafavi, P., Zank, G. P., & Webb, G. M. Structure of Energetic Particle Mediated Shocks Revisited. United States. doi:10.3847/1538-4357/AA6F10.
Mostafavi, P., Zank, G. P., and Webb, G. M. Sat . "Structure of Energetic Particle Mediated Shocks Revisited". United States. doi:10.3847/1538-4357/AA6F10.
@article{osti_22663598,
title = {Structure of Energetic Particle Mediated Shocks Revisited},
author = {Mostafavi, P. and Zank, G. P. and Webb, G. M.},
abstractNote = {The structure of collisionless shock waves is often modified by the presence of energetic particles that are not equilibrated with the thermal plasma (such as pickup ions [PUIs] and solar energetic particles [SEPs]). This is relevant to the inner and outer heliosphere and the Very Local Interstellar Medium (VLISM), where observations of shock waves (e.g., in the inner heliosphere) show that both the magnetic field and thermal gas pressure are less than the energetic particle component pressures. Voyager 2 observations revealed that the heliospheric termination shock (HTS) is very broad and mediated by energetic particles. PUIs and SEPs contribute both a collisionless heat flux and a higher-order viscosity. We show that the incorporation of both effects can completely determine the structure of collisionless shocks mediated by energetic ions. Since the reduced form of the PUI-mediated plasma model is structurally identical to the classical cosmic ray two-fluid model, we note that the presence of viscosity, at least formally, eliminates the need for a gas sub-shock in the classical two-fluid model, including in that regime where three are possible. By considering parameters upstream of the HTS, we show that the thermal gas remains relatively cold and the shock is mediated by PUIs. We determine the structure of the weak interstellar shock observed by Voyager 1 . We consider the inclusion of the thermal heat flux and viscosity to address the most general form of an energetic particle-thermal plasma two-fluid model.},
doi = {10.3847/1538-4357/AA6F10},
journal = {Astrophysical Journal},
number = 1,
volume = 841,
place = {United States},
year = {Sat May 20 00:00:00 EDT 2017},
month = {Sat May 20 00:00:00 EDT 2017}
}