Partition of Temperature Between Electrons and Ions across Collisionless, Fast Mode Shocks
Abstract
A model for the partition of temperature between electrons and ions across collisionless, fast mode shocks is presented. Observations have shown that although the temperature of the electrons and ions increase across the shock, the ion temperature increase is substantially larger than that of the electrons. Understanding this problem is important for a complete understanding of the relationships between collisionless shock parameters and particle behavior across the shock layer. The results of the model may be used for further multifluid and kinetic models of particle entry to the Earth's magnetosphere, as in the polar rain. Our approach focuses on the much simpler behavior of magnetized electrons in the stationary macroscopic electric and magnetic fields of the shock layer. We solve the steady state electron Vlasov equation in the guiding center approximation. The discretionary parts of the upstream and downstream distribution functions f1 and f 2, respectively, are specified using observations as a guide. The shape parameters which characterize f1 and f2 are treated as free parameters in the model. Velocity moments of f1 and f2 provide a closed set of equations which are solved to yield the shape parameters of f1 and f2 with the help of the RankineHugoniot conservation equations and the specification of the deHoffmannTeller potential jump and a few upstream conditions. With the shape parameter solution, we compute the downstream electron temperature by numerical integration. The ion pressure jump and hence temperature is obtained by subtracting the electron pressure jump from the total pressure jump along the normal given by the RankineHugoniot conservation laws. The model recovers the electron temperature jumps of a new ISEE1 data base of 129 Earth bow shock crossings developed and analyzed for the purposes of this thesis. The model also recovers trends in ion temperature jumps at shocks observed by ISEE1 previously cataloged by Thomsen et al. 1987b . With the understanding provided by the Vlasov mapping of f in the coherent forces, a predictive empirical model for the partition of temperature is developed providing a new global view of the electronion downstream partition of temperature at the Earth's bow shock.
 Publication:

Ph.D. Thesis
 Pub Date:
 1998
 Bibcode:
 1998PhDT........20H
 Keywords:

 Physics: Fluid and Plasma, Physics: Astronomy and Astrophysics