A possible closure relation for heat transport in the solar wind
Abstract
IMP electron data are studied with the aim of determining a closure relation describing heat transport in the solar wind. We have compared a simple model of the relative drift speed between coreelectron and proton populations, ∆V_{c}, with measured values. In this model, core electron acceleration responds to the superposition of two opposing forces. The first results from protonelectron Coulomb friction with is characterized by the slowing down time τ_{cp} and tends to accelerate the coreelectron population up to the proton bulk speed. Waveelectron collisions supplement this friction thereby increasing the coreelectron acceleration. The second force results from the macroscopic interplanetary electric and magnetic fields and tends to reduce the core speed to zero with a time constant, τ_{σ}, equal to the bounce preiod of a typical bound electron. At equilibrium, the two opposing forces balance yielding a relation between ∆V_{c} and the solar wind bulk speed in a corotating reference frame, U_{sw}:∆V_{c}=U_{sw}/[1+βτ_{σ}/τ<atother>@qL</atother> _{cp}]. The model predictions are found to agree best with measured values if β?4.5. A model for the heat flux, Q=γN_{c}kT_{c}U_{sw}/ [1+βτ_{σ}/τ_{cp}], with γ=10.7 and β=4.5, implied by the above and previous results, also fits measurements at 1 AU. The results suggest that the model may be useful for closing the Boltzmann moment equations describing the solar wind expansion.
 Publication:

Journal of Geophysical Research
 Pub Date:
 November 1979
 DOI:
 10.1029/JA084iA11p06621
 Bibcode:
 1979JGR....84.6621F
 Keywords:

 Closure Law;
 Heat Transfer;
 Solar Wind;
 Boltzmann Transport Equation;
 Core Flow;
 Coulomb Collisions;
 Electric Fields;
 Electron Energy;
 Electron Scattering;
 Flow Distribution;
 Imp;
 Interplanetary Magnetic Fields;
 Macroscopic Equations;
 Space Radiation