On the electron temperature downstream of the solar wind termination shock

Чашей, И. В.; Fahr, H. J.

doi:10.5194/angeo-31-1205-2013

Cited by 16 publications

(15 citation statements)

References 29 publications

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“…The problem with these models is that the electrons are important for the heat transfer. The behavior of the electrons is not well understood at the termination shock and beyond, but see Chashei & Fahr (2013, 2014. For O star astrospheres, Arthur (2007) included a heat transfer model to avoid too strong adiabatic cooling of the stellar wind at the TS.…”

Section: Heating and Coolingmentioning

confidence: 99%

Shock structures of astrospheres

Scherer

Fichtner

Kleimann

et al. 2016

A&A

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Context. The interaction between a supersonic stellar wind and a (super-)sonic interstellar wind has recently been viewed with new interest. We here first give an overview of the modeling, which includes the heliosphere as an example of a special astrosphere. Then we concentrate on the shock structures of fluid models, especially of hydrodynamic (HD) models. More involved models taking into account radiation transfer and magnetic fields are briefly sketched. Even the relatively simple HD models show a rich shock structure, which might be observable in some objects. Aims. We employ a single-fluid model to study these complex shock structures, and compare the results obtained including heating and cooling with results obtained without these effects. Furthermore, we show that in the hypersonic case valuable information of the shock structure can be obtained from the Rankine-Hugoniot equations. Methods. We solved the Euler equations for the single-fluid case and also for a case including cooling and heating. We also discuss the analytical Rankine-Hugoniot relations and their relevance to observations. Results. We show that the only obtainable length scale is the termination shock distance. Moreover, the so-called thin shell approximation is usually not valid. We present the shock structure in the model that includes heating and cooling, which differs remarkably from that of a single-fluid scenario in the region of the shocked interstellar medium. We find that the heating and cooling is mainly important in this region and is negligible in the regions dominated by the stellar wind beyond an inner boundary.

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Section: Heating and Coolingmentioning

confidence: 99%

Shock structures of astrospheres

Scherer

Fichtner

Kleimann

et al. 2016

A&A

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show abstract

“…The second term in Equation (1) describes the advection with the solar wind with velocity u , p the third term describes diffusion of particles in velocity space, the fourth term describes adiabatic heating/cooling, and the last term describes a source (or sink) for the distribution due to, for example, charge-exchange with interstellar neutral atoms. Other ionization processes are ignored, such as photoionization (which is negligible at large distances from the Sun) and electron-impact ionization (the distribution of electrons in the IHS is not known, even though it has had recent attention, see e.g., Chalov & Fahr 2013;Chashei & Fahr 2013;Scherer et al 2014;Fahr et al 2015;Gruntman 2015).…”

Section: Pui Transportmentioning

confidence: 99%

Using Kappa Functions to Characterize Outer Heliosphere Proton Distributions in the Presence of Charge-Exchange

Zirnstein

McComas

2015

ApJ

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Kappa functions have long been used in the analysis and modeling of suprathermal particles in various space plasmas. In situ observations of the supersonic solar wind show its distribution contains a cold ion core and powerlaw tail, which is well-represented by a kappa function. In situ plasma observations by Voyager, as well as observations of energetic neutral atom (ENA) spectra by the Interstellar Boundary Explorer (IBEX), showed that the compressed and heated inner heliosheath (IHS) plasma beyond the termination shock can also be represented by a kappa function. IBEX exposes the IHS plasma properties through the detection of ENAs generated by chargeexchange in the IHS. However, charge-exchange modifies the plasma as it flows through the IHS, and makes it difficult to ascertain the parent proton distribution. In this paper we investigate the evolution of proton distributions, initially represented by a kappa function, that experience losses due to charge-exchange in the IHS. In the absence of other processes, it is no longer representable by a single kappa function due to the energydependent, charge-exchange process. While one can still fit a kappa function to the evolving proton distribution over limited energy ranges, this yields fitting parameters (pseudo-density, pseudo-temperature, pseudo-kappa index) that depend on the energy range of the fit. We discuss the effects of fitting a kappa function to the IHS proton distribution over limited energy ranges, its dependence on the initial proton distribution properties at the termination shock, and implications for understanding the observations.

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“…The downstream magnetic field is frozen-in into the center-of-mass flow, and all plasma components are eventually comoving with the center-of-mass flow (Chashei & Fahr 2013). The electrons, on the other hand, react in a completely different way to this electric potential.…”

Section: Theoretical Description Of Downstream Electronsmentioning

confidence: 99%

The electron distribution function downstream of the solar-wind termination shock: Where are the hot electrons?

Fahr

Richardson

Verscharen

2015

A&A

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In the majority of the literature on plasma shock waves, electrons play the role of "ghost particles", since their contribution to mass and momentum flows is negligible, and they have been treated as only taking care of the electric plasma neutrality. In some more recent papers, however, electrons play a new important role in the shock dynamics and thermodynamics, especially at the solar-wind termination shock. They react on the shock electric field in a very specific way, leading to suprathermal nonequilibrium distributions of the downstream electrons, which can be represented by a kappa distribution function. In this paper, we discuss why this anticipated hot electron population has not been seen by the plasma detectors of the Voyager spacecraft downstream of the solar-wind termination shock. We show that hot nonequilibrium electrons induce a strong negative electric charge-up of any spacecraft cruising through this downstream plasma environment. This charge reduces electron fluxes at the spacecraft detectors to nondetectable intensities. 6 compared to the classical value λ D in this hot-electron environment. This unusual condition allows for the propagation of a certain type of electrostatic plasma waves that, at very large wavelengths, allow us to determine the effective temperature of the suprathermal electrons directly by means of the phase velocity of these waves. At moderate wavelengths, the electron-acoustic dispersion relation leads to nonpropagating oscillations with the ion-plasma frequency ω p , instead of the traditional electron plasma frequency.

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On the electron temperature downstream of the solar wind termination shock

Cited by 16 publications

References 29 publications

Shock structures of astrospheres

Shock structures of astrospheres

Using Kappa Functions to Characterize Outer Heliosphere Proton Distributions in the Presence of Charge-Exchange

The electron distribution function downstream of the solar-wind termination shock: Where are the hot electrons?

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