Dawn–dusk asymmetry in the Kelvin–Helmholtz instability at Mercury

The NASA MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) spacecraft entered orbital phase around Mercury on 18 March 2011. A surprising consistent feature in the data returned is large-scale vortices that form exclusively on the dusk side of the magnetosphere. Here we presen...

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Veröffentlicht in:Nature communications 2013, Vol.4 (1), p.1645-1645, Article 1645
Hauptverfasser: Paral, Jan, Rankin, Robert
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Sprache:eng
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Zusammenfassung:The NASA MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) spacecraft entered orbital phase around Mercury on 18 March 2011. A surprising consistent feature in the data returned is large-scale vortices that form exclusively on the dusk side of the magnetosphere. Here we present global kinetic hybrid simulations that explain these observations. It is shown that vortices are excited by a Kelvin–Helmholtz instability near the subsolar point, which grows convectively along the dusk-side magnetopause. Virtual time series along a track approximating a flyby of the MESSENGER show correspondence with the satellite data; the data contain sawtooth oscillations in plasma density, flow and magnetic field, and exhibit the observed dawn–dusk asymmetry. It is shown that asymmetry between dawn and dusk at Mercury is controlled by the finite gyroradius of ions and by convection electric fields. Mercury’s magnetosphere offers a natural laboratory for studying plasma regimes not present in other planetary magnetospheres or the laboratory. Recently, the NASA MESSENGER mission reported signatures of Kelvin–Helmholtz instabilities in the magnetic environment of Mercury. Using global hybrid kinetic simulations, Paral and Rankin reproduce these observations, revealing a dawn–dusk asymmetry in the instability.
ISSN:2041-1723
2041-1723
DOI:10.1038/ncomms2676