Electron Energy Partition across Interplanetary Shocks. III. Analysis

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http://hdl.handle.net/10138/314673

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Wilson , L B , Chen , L-J , Wang , S , Schwartz , S J , Turner , D L , Stevens , M L , Kasper , J C , Osmane , A , Caprioli , D , Bale , S D , Pulupa , M P , Salem , C S & Goodrich , K A 2020 , ' Electron Energy Partition across Interplanetary Shocks. III. Analysis ' , Astrophysical Journal , vol. 893 , no. 1 , 22 . https://doi.org/10.3847/1538-4357/ab7d39

Title: Electron Energy Partition across Interplanetary Shocks. III. Analysis
Author: Wilson, Lynn B.; Chen, Li-Jen; Wang, Shan; Schwartz, Steven J.; Turner, Drew L.; Stevens, Michael L.; Kasper, Justin C.; Osmane, Adnane; Caprioli, Damiano; Bale, Stuart D.; Pulupa, Marc P.; Salem, Chadi S.; Goodrich, Katherine A.
Other contributor: University of Helsinki, Department of Physics

Date: 2020-04-10
Language: eng
Number of pages: 21
Belongs to series: Astrophysical Journal
ISSN: 0004-637X
DOI: https://doi.org/10.3847/1538-4357/ab7d39
URI: http://hdl.handle.net/10138/314673
Abstract: An analysis of model fit results of 15,210 electron velocity distribution functions (VDFs), observed within 2 hr of 52 interplanetary (IP) shocks by the Wind spacecraft near 1 au, is presented as the third and final part on electron VDFs near IP shocks. The core electrons and protons dominate in the magnitude and change in the partial-to-total thermal pressure ratio, with the core electrons often gaining as much or more than the protons. Only a moderate positive correlation is observed between the electron temperature and the kinetic energy change across the shock, while weaker, if any, correlations were found with any other macroscopic shock parameter. No VDF parameter correlated with the shock normal angle. The electron VDF evolves from a narrowly peaked core with flaring suprathermal tails in the upstream to either a slightly hotter core with steeper tails or much hotter flattop core with even steeper tails downstream of the weaker and strongest shocks, respectively. Both quasi-static and fluctuating fields are examined as possible mechanisms modifying the VDF, but neither is sufficient alone. For instance, flattop VDFs can be generated by nonlinear ion acoustic wave stochastic acceleration (i.e., inelastic collisions), while other work suggested they result from the combination of quasi-static and fluctuating fields. This three-part study shows that not only are these systems not thermodynamic in nature; even kinetic models may require modification to include things like inelastic collision operators to properly model electron VDF evolution across shocks or in the solar wind.
Subject: Solar wind
Interplanetary shocks
Solar coronal mass ejections
Solar coronal mass ejection shocks
Space plasmas
Plasma astrophysics
Plasma physics
Interplanetary particle acceleration
QUASI-PERPENDICULAR SHOCKS
ION-ACOUSTIC INSTABILITY
HEAT-FLUX INSTABILITY
EARTHS BOW SHOCK
LOW-MACH-NUMBER
SOLAR-WIND
TEMPERATURE EQUILIBRATION
VELOCITY DISTRIBUTIONS
ANOMALOUS RESISTIVITY
COLLISIONLESS SHOCKS
115 Astronomy, Space science
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