A consistent thermodynamics of the MHD wave-heated two-fluid solar wind

Чашей, И. В.; Fahr, H. J.; Lay, G.

doi:10.5194/angeo-21-1405-2003

Cited by 20 publications

(18 citation statements)

References 52 publications

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“…They are, however, directed opposite to the solar wind flow direction, and hence are seen by the solar wind bulk with about twice the solar wind velocity. Since the solar wind carries with it co-convected and ion-selfgenerated magnetoacoustic turbulences (see Chashei et al 2003;Chalov et al 2004Chalov et al , 2006, these shock-reflected ions undergo pitchangle scattering by wave-plasma interactions with these turbulences (see e.g. Chashei et al 2003;Chashei & Fahr 2005).…”

Section: Discussionmentioning

confidence: 99%

“…Since the solar wind carries with it co-convected and ion-selfgenerated magnetoacoustic turbulences (see Chashei et al 2003;Chalov et al 2004Chalov et al , 2006, these shock-reflected ions undergo pitchangle scattering by wave-plasma interactions with these turbulences (see e.g. Chashei et al 2003;Chashei & Fahr 2005). The longer these reflected ions undergo those scattering processes, the more they are redistributed into a pitch-angle isotropic distribution function in which all of these ions are re-populated into a spherical shell in velocity space centred at the upstream solar wind bulk velocity with a shell radius of about twice the solar wind bulk velocity.…”

Section: Discussionmentioning

confidence: 99%

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Ion reflections from the parallel MHD termination shock and a possible injection mechanism into the Fermi-1 acceleration

Fahr¹,

Verscharen²

2008

A&A

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Context. The analysis with our recently developed kinetic solar wind termination shock model for a parallel magnetic field orientation has shown several interesting features of the ion distribution function at the downstream side of the magnetohydrodynamic shock. Among these results, it turned out that a certain amount of ions are provided with a velocity backwards into the shock transition layer by turbulent interaction. Aims. The behaviour of these reflected ions during their second shock transit towards the upstream side is investigated. The reflected particles become an additional ion species in the foreshock region, and their influence on the upstream plasma environment has to be studied and evaluated. Methods. Under the same shock conditions as adopted in our first paper, we treated these reflected ions kinetically with the methods of our model to solve the appropriate Boltzmann-Vlasov equation. The modified transport equation was solved with the help of stochastic differential equations. Results. The shock scenario leads to fast ion beams oriented backwards into the foreshock region. About 18% of the incoming solar wind ions are reflected and affect the upstream plasma flow. With these properties the treated processes clearly indicate an additional injection mechanism for ACRs.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Ion reflections from the parallel MHD termination shock and a possible injection mechanism into the Fermi-1 acceleration

Fahr¹,

Verscharen²

2008

A&A

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“…With respect to the proton bulk frame they thereby lose an energy ∆ f , taken as the pitch-angle average, given by (see Fahr & Chashei 2002;Chashei et al 2003):…”

Section: Outlook: Competing Proton Relaxation Processes In Heliosphermentioning

confidence: 99%

A kinetic control of the heliospheric interface hydrodynamics of charge-exchanging fluids

Fahr

Bzowski

2004

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Abstract.It is well known that the Solar System is presently moving through a partially ionized local interstellar medium. This gives rise to a counter-flow situation requiring a consistent description of behaviour of the two fluids -ions and neutral atoms -which are dynamically coupled by mutual charge exchange processes. Solutions to this problem have been offered in the literature, all relying on the assumption that the proton fluid, even under evidently nonequilibrium conditions, can be expected to stay in a highly-relaxated distribution function given by mono-Maxwellians shifted by the local proton bulk velocity. Here we check the validity of this assumption, calculating on the basis of a Boltzmann-kinetic approach the actually occurring deviations. As we show, especially for low degrees of ionization, ξ ≤ 0.3, both the H-atoms and protons involved do generate in the heliospheric interface clearly pronounced deviations from shifted Maxwellians with asymmetrically shaped distribution functions giving rise to non-convective transport processes and heat conduction flows. Also in the inner heliosheath region and in the heliotail deviations of the proton distribution from the hydrodynamic one must be expected. This sheds new light on the correctness of current calculations of H-atom distribution functions prevailing in the inner heliosphere and also of the Lyman-α absorption features in stellar spectra due to the presence of the hydrogen wall atoms. Deviations from LTE-functions would be even more pronounced in magnetic interfaces, which via CGL-effects cause temperature anisotropies to arise.

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“…With the free energy of this unstable distribution, these ions drive Alfvenic wave power enforcing pitch-angle isotropization of the initial velocity distribution (see Chalov & Fahr 1998. Due to wave-wave coupling, the wave energy generated by primary PUIs is transported diffusively in wave-vector space both to shorter wavelengths, where it can be absorbed by solar wind protons, and to longer wavelengths, where it is reabsorbed by all PUIs (Chashei et al 2003;Chalov et al 2006). It turns out that only a small fraction of about 5 percent of the PUI-generated wave energy reappears in the observed proton temperatures, while about 50 percent is reabsorbed by PUIs.…”

Section: Introduction: the Multi-fluid Character Of The Solar Windmentioning

confidence: 99%

Supersonic solar wind ion flows downstream of the termination shock explained by a two-fluid shock model

Fahr¹,

Chalov²

2008

A&A

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In the view of classic magnetohydrodynamics, it is generally expected that at a shock the supersonic upstream flow is converted into the subsonic downstream flow whereby the increased entropy appears in the increased downstream temperature. In the solar wind termination shock, it is expected that the supersonic upstream solar wind ion flow changes into a subsonic downstream ion flow. The Voyager-2 passage over this shock, however, demonstrated that the downstream solar wind ion flow still has a supersonic signature. In this paper, we present straightforward solution to this unexpected phenomenon by applying a two-fluid model to describe the passage of the solar wind over the termination shock. The two dynamically dependent, but thermodynamically independent fluids are the normal solar wind ions and the comoving suprathermal ions, or so-called pick-up ions. As we can show, the downstream solar wind ion flow can be either subsonic or supersonic depending on the upstream effective Mach number of the flow or the pick-up ion pressure. This is because most of the kinetic energy of the upstream flow is converted into thermal energy of the suprathermal ions, while the normal solar wind ions are heated only ineffectively, so that they can retain a supersonic signature even further downstream. With this two-fluid model, we can explain the main features of the shock structure observed by Voyager-2.

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A consistent thermodynamics of the MHD wave-heated two-fluid solar wind

Cited by 20 publications

References 52 publications

Ion reflections from the parallel MHD termination shock and a possible injection mechanism into the Fermi-1 acceleration

Ion reflections from the parallel MHD termination shock and a possible injection mechanism into the Fermi-1 acceleration

A kinetic control of the heliospheric interface hydrodynamics of charge-exchanging fluids

Supersonic solar wind ion flows downstream of the termination shock explained by a two-fluid shock model

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