Transport Phenomena in a Completely Ionized Gas

Spitzer, Lyman; Härm, Richard

doi:10.1103/physrev.89.977

Cited by 2,128 publications

(1,170 citation statements)

References 5 publications

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“…Compared to the transport coefficients computed by Spitzer and Härm [1953] using kinetic theory, the eight-moment value for the thermoelectric coefficient is very good, but the eight-moment value for the electron thermal conductivity is too small by more than a factor of 2 [Schunk, 1975]. Thus, while the model uses the eight-moment result for the thermoelectric term, it uses the widely used Banks [1966] expression for the electron thermal conductivity instead.…”

Section: Thermal Electron Equationsmentioning

confidence: 99%

Heating of the sunlit polar cap ionosphere by reflected photoelectrons

2014

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Photoelectrons escape from the ionosphere on sunlit polar cap field lines. In order for those field lines to carry zero current without significant heavy ion outflow or cold electron inflow, field-aligned potential drops must form to reflect a portion of the escaping photoelectron population back to the ionosphere. Using a 1-D ionosphere-polar wind model and measurements from the Resolute Bay Incoherent Scatter Radar (RISR-N), this paper shows that these reflected photoelectrons are a significant source of heat for the sunlit polar cap ionosphere. The model includes a kinetic suprathermal electron transport solver, and it allows energy input from the upper boundary in three different ways: thermal conduction, soft precipitation, and potentials that reflect photoelectrons. The simulations confirm that reflection potentials of several tens of eV are required to prevent cold electron inflow and demonstrate that the flux tube integrated change in electron heating rate (FTICEHR) associated with reflected photoelectrons can reach 10 9 eV cm −2 s −1 . Soft precipitation can produce FTICEHR of comparable magnitudes, but this extra heating is divided among more electrons as a result of electron impact ionization. Simulations with no reflected photoelectrons and with downward field-aligned currents (FAC) primarily carried by the escaping photoelectrons have electron temperatures which are ∼250-500 K lower than the RISR-N measurements in the 300-600 km region; however, simulations with reflected photoelectrons, zero FAC, and no other form of heat flux through the upper boundary can satisfactorily reproduce the RISR-N data.

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Section: Thermal Electron Equationsmentioning

confidence: 99%

Heating of the sunlit polar cap ionosphere by reflected photoelectrons

2014

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“…The modified thermal conductivity to be used in the simulations is then given by K C = e ; K SH , where K W is the classical SpitzerHarm thermal conductivity [Spitzer and Harm, 1953). By considering a dipole magnetic field, we can see that B L will vary somewhat with L-shell.…”

Section: Physical Mechanism and Mathematical Modelmentioning

confidence: 99%

A modified thermal conductivity for low density plasma magnetic flux tubes

Comfort

Craven

Richards

1995

Geophysical Research Letters

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Abstract. In response to inconsistencies which have arisen in results from a hydrodynamic model in simulations of high ion temperatures (1-2 eV) observed in low density, outer plasmasphere flux tubes, we postulate a reduced thermal conductivity coefficient in which only particles in the loss cone of the quasicollisionless plasma contribute to the thermal conduction. Other particles are assumed to magnetically mirror before they reach the topside ionosphere and therefore not to remove thermal energy from the plasmasphere. This concept is used to formulate a mathematically simple, but physically limiting model for a modified thermal conductivity coefficient. When this modified coefficient is employed in the hydrodynamic model in a case study, the inconsistencies between simulation results and observations are largely resolved. The high simulated ion temperatures are achieved with significantly less heat input, and result in substantially lower ion temperatures in the topside ionosphere. We suggest that this mechanism may be operative under the limited low density, refilling conditions in which high ion temperatures are observed.

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“…Binary mixtures in which the temperatures are equal have been treated in literature for dilute gases [1,2,3], both in the case of inert components as well as those composed by charged particles thus leading to the study of plasmas [4,5,6,7]. These have been studied with kinetic theory when temperatures of ions and electrons are equal [8,9,10,11], and other authors.…”

Section: Introductionmentioning

confidence: 99%

Relaxation time for the temperature in a dilute binary mixture from classical kinetic theory

Moratto¹,

García‐Colín²

2011

Journal of Non-Equilibrium Thermodynamics

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The system of our interest is a dilute binary mixture, in which we consider that the species have different temperatures as an initial condition. To study their time evolution, we use the full version of the Boltzmann equation, under the hypothesis of partial local equilibrium for both species. Neither a diffusion force nor mass diffusion appears in the system. We also estimate the time in which the temperatures of the components reach the full local equilibrium. In solving the Boltzmann equation, we imposed no assumptions on the collision term.We work out its solution by using the well known Chapman-Enskog method to first order in the gradients. The time in which the temperatures relax is obtained following Landau's original idea. The result is that the relaxation time for the temperatures is much smaller than the characteristic hydrodynamical times but greater than a collisional time. The main conclusion is that there is no need to study binary mixtures with different temperatures when hydrodynamical properties are sought.

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Transport Phenomena in a Completely Ionized Gas

Cited by 2,128 publications

References 5 publications

Heating of the sunlit polar cap ionosphere by reflected photoelectrons

Heating of the sunlit polar cap ionosphere by reflected photoelectrons

A modified thermal conductivity for low density plasma magnetic flux tubes

Relaxation time for the temperature in a dilute binary mixture from classical kinetic theory

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