The Kelvin–Helmholtz instability at Venus: What is the unstable boundary?
| Autor: | Daniil Korovinskiy, U. V. Möstl, Helfried K. Biernat, Nikolay Erkaev, Michael Zellinger, Hannes Gröller, Helmut Lammer |
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| Rok vydání: | 2011 |
| Předmět: |
Solar System
010504 meteorology & atmospheric sciences Solar wind Venus Astrophysics 01 natural sciences Instability Article 0103 physical sciences 010303 astronomy & astrophysics 0105 earth and related environmental sciences Physics biology Astronomy and Astrophysics Mechanics biology.organism_classification Vortex Boundary layer Magnetospheres Space and Planetary Science Physics::Space Physics Magnetopause Astrophysics::Earth and Planetary Astrophysics Magnetohydrodynamics |
| Zdroj: | Icarus |
| ISSN: | 0019-1035 |
| Popis: | Highlights ► We study the Kelvin–Helmholtz instability at boundary layers around of Venus. ► The stability of the induced magnetopause and the ionopause is examined. ► The ionopause seems to be stable due to a large density jump across this boundary. ► The instability evolves into its nonlinear phase on the magnetopause at solar maximum. ► Loss rates are therefore lower than previously assumed. The Kelvin–Helmholtz instability gained scientific attention after observations at Venus by the spacecraft Pioneer Venus Orbiter gave rise to speculations that the instability contributes to the loss of planetary ions through the formation of plasma clouds. Since then, a handful of studies were devoted to the Kelvin–Helmholtz instability at the ionopause and its implications for Venus. The aim of this study is to investigate the stability of the two instability-relevant boundary layers around Venus: the induced magnetopause and the ionopause. We solve the 2D magnetohydrodynamic equations with the total variation diminishing Lax–Friedrichs algorithm and perform simulation runs with different initial conditions representing the situation at the boundary layers around Venus. Our results show that the Kelvin–Helmholtz instability does not seem to be able to reach its nonlinear vortex phase at the ionopause due to the very effective stabilizing effect of a large density jump across this boundary layer. This seems also to be true for the induced magnetopause for low solar activity. During high solar activity, however, there could occur conditions at the induced magnetopause which are in favour of the nonlinear evolution of the instability. For this situation, we estimated roughly a growth rate for planetary oxygen ions of about 7.6 × 1025 s−1, which should be regarded as an upper limit for loss due to the Kelvin–Helmholtz instability. |
| Databáze: | OpenAIRE |
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