Transfer integrals for fully ionized gases

Fichtner, H.; Sreenivasn, S. Ranga; Vormbrock, N.

doi:10.1017/s0022377800018699

Cited by 5 publications

(2 citation statements)

References 27 publications

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“…Thus higher order approximations of the Taylor expansions are required. Because this leads to clumsy expressions, which also need a lot of computational effort, it may be better for practical purposes to solve the collision integrals numerically as in Fichtner et al (1996).…”

Section: Charge Exchange With Particles Of Different Massesmentioning

confidence: 99%

Ionization rates in the heliosheath and in astrosheaths

Scherer

Fichtner

Ferreira

et al. 2014

A&A

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Context. In the heliosphere, especially in the inner heliosheath, mass-, momentum-, and energy-loading induced by the ionization of neutral interstellar species plays an important, but for some species, especially helium, an underestimated role. Aims. We discuss the implementation of charge exchange and electron impact processes for interstellar neutral hydrogen and helium and their implications for the subsequent modeling. We especially emphasize the importance of electron impact and a more sophisticated numerical treatment of the charge exchange reactions. Moreover, we discuss the nonresonant charge exchange effects. Methods. We discuss rate coefficients and revise the influence of the cross-sections in the (magneto-)hydrodynamic equations for different reactions and also their representation in the collision integrals. Results. Electron impact is in some regions of the heliosphere, particularly in the heliotail, more effective than charge exchange, and the ionization of neutral interstellar helium contributes about 40% to the mass-and momentum-loading in the heliosheath. The charge exchange cross-sections need to be modeled with higher accuracy, especially in view of the latest developments made in describing them. Conclusions. The ionization of helium and the electron impact ionization of hydrogen need to be taken into account in modeling the heliosheath and, in general, astrosheaths. Moreover, the charge exchange cross-sections need to be handled in a more sophisticated way, either by developing better analytic approximations or by numerically solving the collision integrals.

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Section: Charge Exchange With Particles Of Different Massesmentioning

confidence: 99%

Ionization rates in the heliosheath and in astrosheaths

Scherer

Fichtner

Ferreira

et al. 2014

A&A

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“…These collisional values, therefore, do not take into account the transfer between the ions and the suprathermal electrons. Fichtner et al (1996) studied the collisional transfers based on a number of distribution functions. Their results indicated that the transfer values for some non-Maxwellian distributions could be significantly different from those for a Maxwellian.…”

Section: Kinetic Suprathermal Electron Effectsmentioning

confidence: 99%

Comparison of the effects of wave-particle interactions and the kinetic suprathermal electron population on the acceleration of the solar wind

Tam

Chang

2002

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Abstract. Kinetic effects due to wave-particle interactions and suprathermal electrons have been suggested in the literature as possible solar wind acceleration mechanisms. Ion cyclotron resonant heating, in particular, has been associated with some qualitative features observed in the solar wind. In terms of solar wind acceleration, however, it is interesting to compare the kinetic effects of suprathermal electrons with those due to the wave-particle interactions. The combined effects of the two acceleration mechanisms on the fast solar wind have been studied by Tam & Chang (1999a,b). In this study, we investigate the role of the suprathermal electron population in the acceleration of the solar wind. Our model follows the global kinetic evolution of the fast solar wind under the influence of ion cyclotron resonant heating, while taking into account Coulomb collisions, and the ambipolar electric field that is consistent with the particle distributions themselves. The kinetic effects due to the suprathermal electrons, which we define to be the tail of the electron distributions, can be included in the model as an option. By comparing the results with and without the inclusion of the suprathermal electron effects, we determine the relative importance of suprathermal electrons and wave-particle interactions in driving the solar wind. We find that although suprathermal electrons enhance the ambipolar electric potential in the solar wind considerably, their overall influence as an acceleration mechanism is relatively insignificant in a wave-driven solar wind.

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