Electron energy partition across interplanetary shocks: III. Analysis. (arXiv:2001.09231v1 [physics.space-ph])
<a href="http://arxiv.org/find/physics/1/au:+Wilson_L/0/1/0/all/0/1">L.B. Wilson III</a>, <a href="http://arxiv.org/find/physics/1/au:+Chen_L/0/1/0/all/0/1">Li-Jen Chen</a>, <a href="http://arxiv.org/find/physics/1/au:+Wang_S/0/1/0/all/0/1">Shan Wang</a>, <a href="http://arxiv.org/find/physics/1/au:+Schwartz_S/0/1/0/all/0/1">Steven J. Schwartz</a>, <a href="http://arxiv.org/find/physics/1/au:+Turner_D/0/1/0/all/0/1">Drew L. Turner</a>, <a href="http://arxiv.org/find/physics/1/au:+Stevens_M/0/1/0/all/0/1">Michael L. Stevens</a>, <a href="http://arxiv.org/find/physics/1/au:+Kasper_J/0/1/0/all/0/1">Justin C. Kasper</a>, <a href="http://arxiv.org/find/physics/1/au:+Osmane_A/0/1/0/all/0/1">Adnane Osmane</a>, <a href="http://arxiv.org/find/physics/1/au:+Caprioli_D/0/1/0/all/0/1">Damiano Caprioli</a>, <a href="http://arxiv.org/find/physics/1/au:+Bale_S/0/1/0/all/0/1">Stuart D. Bale</a>, <a href="http://arxiv.org/find/physics/1/au:+Pulupa_M/0/1/0/all/0/1">Marc P. Pulupa</a>, <a href="http://arxiv.org/find/physics/1/au:+Salem_C/0/1/0/all/0/1">Chadi S. Salem</a>, <a href="http://arxiv.org/find/physics/1/au:+Goodrich_K/0/1/0/all/0/1">Katherine A. Goodrich</a>
Analysis of model fit results of 15,210 electron velocity distribution
functions (VDFs), observed within $pm$2 hours 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.
Analysis of model fit results of 15,210 electron velocity distribution
functions (VDFs), observed within $pm$2 hours 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.
http://arxiv.org/icons/sfx.gif
