On the model of the solar wind-interstellar medium interaction with two shock waves

Баранов, В. Б.; Krasnobaev, K. V.

doi:10.1007/bf00646195

Cited by 37 publications

(28 citation statements)

References 7 publications

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“…(1 b) Field-plasma interface according to Parker (1963). (1 c) Plasma-plasma interface for supersonic LISM flow according to Baranov et al, (1979). (ld) Plasma-plasma interface model with inclusion of plasma diffusion across the heliopause according to Neutsch and Fahr (1983).…”

Section: The Heliopause As a Tangential Discontinuitymentioning

confidence: 99%

Plasma transport across the heliopause

et al. 1986

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Existing heliopause models are critically rediscussed under the new aspect of possible plasma mixing between the solar wind and the ambient ionized component of the local interstellar medium (LISM). Based on current kinetic plasma theories, effective diffusion rates across the heliopause are evaluated for several models with turbulence caused by electrostatic or electromagnetic interactions that could be envisaged in this context. Some specific cases that may lead to high diffusion rates are investigated, especially in regard to their LISM magnetic field dependence.For weak fields (less than 10-7 G), macroscopic hydrodynamic instabilities, such as of Rayleigh-Taylor or Kelvin-Helmholtz-types, can be excited. The resulting plasma mixing rates at the heliopause may amount to 20-30% of the impinging mass flow.Recently, an unconventional new approach to the problem for the case of tangential magnetic fields at the heliopause was published in which a continuous change of the plasma properties within an extended boundary layer is described by a complete set of two-fluid plasma equations including a hybrid MHD-formnlation of wave-particle interaction effects. If a neutral sheet is assumed to exist within the boundary layer, the magnetic field direction is proven to be constant for a plane-parallel geometry. Considering the electric fields and currents in the layer, an interesting relationship between the field-reconnection probability and the electric conductivity can be derived, permitting a quantitative determination of either of these quantities.An actual value for the electrical conductivity is derived here on the basis of electron distribution functions given by a superposition of Maxwellians with different temperatures. Using two-stream instability theory and retaining only the most unstable modes, an exact solution for the density, velocity, and magnetic and electric fields can be obtained. The electrical conductivity is then shown to be six orders of magnitude lower than calculated by conventional formulas. Interestingly, this leads to an acceptable value of 0.1 for the reconnection coefficient.By analogy with the case of planetary magnetopauses, it is shown here for LISM magnetic fields of the order of 10-6 G or larger that field reconnection processes may also play an important role for the plasma mixing at the heliopause. The resulting plasma mixing rate is estimated to amount to an average value of 10 % of the incident mass flow. It is suggested here that the dependence of the cosmic-ray penetration into the heliosphere on the distribution of reconnecting areas at the heliopause may provide a means of deriving the strength and orientation of the LISM field.A series of observational implications for the expected plasma mixing at the heliopause is discussed in the last part of the paper. In particular, consequences are discussed for the generation of radio noise at the heliopause, for the penetration of LISM neutrals into the heliosphere, for the propagation of cosmic rays towards the inner part of the solar s...

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Section: The Heliopause As a Tangential Discontinuitymentioning

confidence: 99%

Plasma transport across the heliopause

et al. 1986

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“…Cantó & Raga (1998) and more recently in Schulreich & Breitschwerdt (2011); the physics of mixing layers is discussed in e.g. Baranov et al (1976), Cantó & Raga (1991) and Raga et al (1995).…”

Section: Introductionmentioning

confidence: 99%

Non-thermal processes in bowshocks of runaway stars

Valle¹,

Romero²

2012

A&A

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Context. Runaway massive stars are O-and B-type stars with high spatial velocities with respect to the interstellar medium. These stars can produce bowshocks in the surrounding gas. Bowshocks develop as arc-shaped structures, with bows pointing to the same direction as the stellar velocity, while the star moves supersonically through the interstellar gas. The piled-up shocked matter emits thermal radiation and a population of locally accelerated relativistic particles is expected to produce non-thermal emission over a wide range of energies. Aims. We aim to model the non-thermal radiation produced in these sources. Methods. Under some assumptions, we computed the non-thermal emission produced by the relativistic particles and the thermal radiation caused by free-free interactions, for O4I and O9I stars. We applied our model to ζ Oph (HD 149757), an intensively studied massive star seen from the northern hemisphere. This star has spectral type O9.5V and is a well-known runaway. Results. Spectral energy distributions of massive runaways are predicted for the whole electromagnetic spectrum. Conclusions. We conclude that the non-thermal radiation might be detectable at various energy bands for relatively nearby runaway stars, especially at high-energy gamma rays. Inverse Compton scattering with photons from the heated dust gives the most important contribution to the high-energy spectrum. This emission approaches Fermi sensitivities in the case of ζ Oph.

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“…This region is bounded by the bow shock that decelerates and compresses the interstellar medium flow and by the termination shock that decelerates and compresses the solar wind flow (see e.g. Baranov et al 1970Baranov et al , 1976Baranov 1990). Between these two shocks there is a region with a strong transverse gradient of the velocity component parallel to the shocks.…”

Section: √ S/(1 + S)mentioning

confidence: 99%

“…The velocity variation, V m , through the heliopause ranges from zero to about 75 km s −1 in the portion of the interaction region where the flow can be considered as incompressible (see e.g. Baranov et al 1976;Ruderman et al 2004). A typical value of the electron number density in the interstellar medium is about 0.1 cm −3 .…”

Section: √ S/(1 + S)mentioning

confidence: 99%

Stability of an MHD shear flow with a piecewise linear velocity profile

Brevdo

2006

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In this paper we present the results of the stability analysis of a simple shear flow of an incompressible fluid with a piecewise linear velocity profile in the presence of a magnetic field. In the flow, a finite transitional magnetic-free layer with a linear velocity profile is sandwiched by two semi-infinite regions. One of these regions is magnetic-free and the flow velocity in the region is constant. The other region is magnetic and the fluid in it is quiescent. The magnetic field is constant and parallel to the flow in the transitional layer. The fluid density is constant both in the magnetic as well as the magnetic-free regions, while it has a jump-type discontinuity at the boundary between the transitional layer and the magnetic region. The effect of gravity is included in the model, and it is assumed that the lighter fluid is overlaying the heavier one, thus no Rayleigh-Taylor instability is present. The dispersion equation governing the normal-mode stability of the flow is derived and its properties are analysed. We study stability of two cases: (i) magnetic-free flow in the presence of gravity, and (ii) magnetic flow without gravity. In the first case, the flow stability is controlled by the Rayleigh number, R. In the second case, the control parameter is the inverse squared Alfvénic Mach number, H. Stability of a particular monochromatic perturbation also depends on its dimensionless wavenumber α. We combine the analytical and numerical approaches to obtain the neutral stability curves in the (α, R)-plane in the case of the magnetic-free flow, and in the (α, H)-plane in the case of the magnetic flow. The dependence of the instability increment on R in the first case, and on H in the second case is treated. We apply the results of the analysis to the stability of a strongly subsonic portion of the heliopause. Our main conclusion is as follows: The inclusion of a transitional layer near the heliopause into the model increases by an order of magnitude the strength of the interstellar magnetic field required to stabilize this portion of the heliopause in comparison with the corresponding stabilizing strength of the magnetic field required when modelling the heliopause as a tangential discontinuity.

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On the model of the solar wind-interstellar medium interaction with two shock waves

Cited by 37 publications

References 7 publications

Plasma transport across the heliopause

Plasma transport across the heliopause

Non-thermal processes in bowshocks of runaway stars

Stability of an MHD shear flow with a piecewise linear velocity profile

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