Microphysics of the Venusian and Martian mantles

Quest, K. B.; Shapiro, V. D.; Szegö, K.; Dóbé, Z.

doi:10.1029/96gl03972

Cited by 17 publications

(14 citation statements)

References 10 publications

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“…1. Smaller k values yield results similar to those obtained in [18], and will not be discussed here. Figure 2 illustrates an evolution in time of the bulk momentum of the solar-wind protons [ Fig.…”

supporting

confidence: 66%

“…The simulation results are obtained with a one-dimensional hybrid kinetic code described in Ref. [18]. The code treats the two ion species (protons and oxygen) using particle-in-cell methods while the electrons are modeled as a fluid in which inertial and electromagnetic effects are retained.…”

mentioning

confidence: 99%

“…frame, boundary conditions (periodic in x), and initialization (uniform relative drift between Maxwellian protons and ions) of the simulation are the same as that used in Ref. [18], with the difference that waves are allowed to propagate at an arbitrary angle with respect to the ambient magnetic field. The parameters used in the simulation are following.…”

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Interaction of the Solar Wind with Unmagnetized Planets

et al. 1999

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The results of a one-dimensional electromagnetic hybrid simulation of the interaction between the ionospheres of Venus and Mars and the solar wind are presented. Finite electron inertia is retained, allowing for the analysis of the lower hybrid waves propagating along an oblique but fixed angle to the shocked solar-wind magnetic field. The waves are excited by a relative drift between a cold electron beam, created by E 3 B pickup, and the planetary oxygen ions. The free energy source for instability is in the solar-wind proton flow supporting electron drift through the convective electric field. The waves generate a collective friction between the shocked solar-wind flow and planetary ions. PACS numbers: 96.50.Ek, Because Venus and Mars do not possess a significant intrinsic magnetic field, the ionosphere is the main, however weak, obstacle to the solar-wind flow, and the planetary bow shocks are located quite close to the planets. The ionospheres of both planets are directly exposed to the streaming shocked solar wind. Data from the particle and wave instruments onboard the Pioneer Venus Orbiter (PVO) and Phobos-2 spacecraft show the existence of a thin D ϳ 100 km turbulent transition region between the shocked solar wind and the ionospheres of Venus and Mars, referred to as the plasma mantle [1]. In the mantle, plasmas of both solar wind and ionospheric origin are present in comparable densities n 10 2 cm 23 , but with very different temperatures. The solar-wind proton (electron) temperature is approximately 100 (30) eV, and the drift velocity is close to the proton thermal velocity. The planetary oxygen and electron temperature is close to 1 eV. There is also experimental evidence for the presence of superthermal oxygen [2] and electron populations [3,4] at Mars and Venus. Large tailward escape of planetary ions, most probably originating from the dayside mantle, was also observed at Mars [5].Since the mantle thickness is much less than the ion gyroradius, the usual scheme of E 3 B pickup of the planetary ions by the solar wind is not applicable. The scenario that collective friction due to waves must be responsible for the observed tailward ion escape was formulated first for the Mars mantle in [6], and then for the Venus mantle [7]. This point of view is now widely accepted in other papers [8][9][10]. Intense wave activity was observed at the dayside Venusian mantle by the 100 Hz channel of the electric field detector on the PVO, with typical average amplitudes around tens of mV͞m [11]. Even stronger wave activity in the 5 50 Hz frequency range was measured at the boundary of the Mars ionosphere [12].The modified two stream instability (MTSI) [6][7][8] and the ion acoustic current driven instability [13] have both been suggested as explanations of the observed wave activ-ity. The scenarios of wave activity developing from these two instabilities are quite different. The MTSI results in the excitation of sufficiently long wavelength oscillations with the typical wavelength of the order of the solar-wind elect...

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Interaction of the Solar Wind with Unmagnetized Planets

et al. 1999

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“…Efforts in this direction have been advanced by Shapiro et al [1995] and Dobe et al [1999] through studies of the Landau damping in nonlinear interactions of unstable hydrodynamic waves with planetary ions; they have also considered dissipation processes associated with the momentum transport [Quest et al, 1997]. At present there is only scant information available on the manner in which electric and magnetic field fluctuations serve in the direct exchange of plasma momentum between the solar wind and the ionospheric particles.…”

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confidence: 99%

Plasma transition at the flanks of the Venus ionosheath: Evidence from the Venus Express data

et al. 2011

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[1] Measurements conducted with the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-4) instrument in the Venus Express spacecraft reveal the presence of a plasma transition within a boundary layer that extends along at the flanks of the Venus ionosheath and where the solar wind exhibits changes similar to those reported from previous missions (Mariner 5, Venera, and Pioneer Venus). At the plasma transition there is a sharp downstream decrease in the density of the solar wind electrons and a sudden increase in their temperature embedded within the boundary layer where more gradual changes in the speed, temperature, and density of the solar wind ions are observed. The ASPERA-4 data also show important fluxes of planetary ions measured downstream from the plasma transition and whose dominant velocity component is in the Sun-Venus direction. The speed of those ions is slower than the local solar wind speed and thus is different from that expected from the convective electric field acceleration in which both speed values should be comparable. The boundary layer is interpreted as representing a feature that results from the transport of solar wind momentum to the Venus upper ionosphere, and the ASPERA-4 data provide information on the kinetic properties of the eroded planetary ion population that is seen to stream mostly in the Sun-Venus direction. From the comparison of the ASPERA-4 measurements with those of the magnetic field obtained with the magnetometer of the Venus Express, it is found that in the near wake crossing of the plasma transition the magnetic field intensity decreases to lower values with downstream distance from the planet in agreement with measurements conducted with the Mariner 5 and the PVO. From the analysis of data for orbits with evidence of the plasma transition within the boundary layer, it is found that the momentum flux of planetary ions measured in the wake can be accounted for from the incident momentum flux of the solar wind protons implying an approximate balance as would result from the transport of solar wind momentum to the planetary particles.

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“…The precise mechanisms responsible for the momentum transport processes we describe in terms of an anomalous viscosity have been addressed by Shapiro et al (1995) and Quest et al (1997). They propose that viscosity could be related to wave-particle interactions given the strongly fluctuating magnetic field in the ionosheath as measured by Mariner 5.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of the viscous interaction of the solar wind with the magnetic polar regions of Venus

Reyes-Ruiz

Díaz-Méndez

Pérez‐de‐Tejada

2008

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Aims. We aim to study the viscous interaction of the solar wind with the ionosphere of Venus in the magnetic polar regions by means of hydrodynamical computer simulations. Methods. We use a finite difference code developed for the solution of the Navier-Stokes, continuity and energy equations. Results. We have calculated the flow properties, the shape and location of the boundary layer and the shock formed as a consequence of the viscous interaction over the magnetic poles of the planet and advected downstream. By comparing our results to the flow properties measured by the Venera 10 and Mariner 5 spacecraft in the Venus ionosheath, we determine that a Reynolds number for the flow near the value Re = 20 is necessary to reproduce the position of the intermediate transition as well as the shock front. Also, on the basis of our results we predict the existence of a stagnation region for the solar wind flow extending considerably upstream from the viscous interaction region.

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Microphysics of the Venusian and Martian mantles

Cited by 17 publications

References 10 publications

Interaction of the Solar Wind with Unmagnetized Planets

Interaction of the Solar Wind with Unmagnetized Planets

Plasma transition at the flanks of the Venus ionosheath: Evidence from the Venus Express data

Numerical simulation of the viscous interaction of the solar wind with the magnetic polar regions of Venus

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