The structure of Kelvin–Helmholtz vortices with super-sonic flow

Kobayashi, Yotaro; Kato, Mariko; Nakamura, Kei; Nakamura, Takashi; Fujimoto, M.

doi:10.1016/j.asr.2007.04.016

Cited by 14 publications

(14 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The sonic Mach number has an opposite effect, with higher growth rates for low M S . According to linear theory, flow shears with M S ≥ 2 should in principle be stable [e.g., Miura and Pritchett , 1982], but simulations by Miura [1990] and Kobayashi et al [2008] have shown that KH waves can develop no matter how large the sonic Mach number. Although the Mach numbers in the solar wind should be slightly lower at Mercury's orbit, the magnetosheath profile should follow a behavior similar to that given by Spreiter et al [1966], and the relative effect on the KH growth rates should be limited.…”

Section: Discussionmentioning

confidence: 99%

MESSENGER orbital observations of large‐amplitude Kelvin‐Helmholtz waves at Mercury's magnetopause

et al. 2012

View full text Add to dashboard Cite

[1] We present a survey of Kelvin-Helmholtz (KH) waves at Mercury's magnetopause during MESSENGER's first Mercury year in orbit. The waves were identified on the basis of the well-established sawtooth wave signatures that are associated with nonlinear KH vortices at the magnetopause. MESSENGER frequently observed such KH waves in the dayside region of the magnetosphere where the magnetosheath flow velocity is still subsonic, which implies that instability growth rates at Mercury's magnetopause are much larger than at Earth. We attribute these greater rates to the limited wave energy dissipation in Mercury's highly resistive regolith. The wave amplitude was often on the order of 100 nT or more, and the wave periods were $10-20 s. A clear dawn-dusk asymmetry is present in the data, in that all of the observed wave events occurred in the postnoon and duskside sectors of the magnetopause. This asymmetry is likely related to finite Larmor-radius effects and is in agreement with results from particle-in-cell simulations of the instability. The waves were observed almost exclusively during periods when the north-south component of the magnetosheath magnetic field was northward, a pattern similar to that for most terrestrial KH wave events. Accompanying plasma measurements show that the waves were associated with the transport of magnetosheath plasma into the magnetosphere.

show abstract

Section: Discussionmentioning

confidence: 99%

MESSENGER orbital observations of large‐amplitude Kelvin‐Helmholtz waves at Mercury's magnetopause

et al. 2012

View full text Add to dashboard Cite

show abstract

“…5,34 Recent hydrodynamical simulations, however, have suggested that even in the supersonic shearing flow, the KHI can grow in the subsonic downstream region of the shock wave. 35 Thus, the stronger shear case could be greatly complicated with direct coupling between the ion and electron kinetic equilibrium-associated processes, the shock wave, and the KHI.…”

Section: Some Remarks On the Future Workmentioning

confidence: 99%

Kinetic effects on the Kelvin–Helmholtz instability in ion-to-magnetohydrodynamic scale transverse velocity shear layers: Particle simulations

2010

View full text Add to dashboard Cite

Ion-to-magnetohydrodynamic scale physics of the transverse velocity shear layer and associated Kelvin-Helmholtz instability (KHI) in a homogeneous, collisionless plasma are investigated by means of full particle simulations. The shear layer is broadened to reach a kinetic equilibrium when its initial thickness is close to the gyrodiameter of ions crossing the layer, namely, of ion-kinetic scale. The broadened thickness is larger in B⋅Ω<0 case than in B⋅Ω>0 case, where Ω is the vorticity at the layer. This is because the convective electric field, which points out of (into) the layer for B⋅Ω<0 (B⋅Ω>0), extends (reduces) the gyrodiameters. Since the kinetic equilibrium is established before the KHI onset, the KHI growth rate depends on the broadened thickness. In the saturation phase of the KHI, the ion vortex flow is strengthened (weakened) for B⋅Ω<0 (B⋅Ω>0), due to ion centrifugal drift along the rotational plasma flow. In ion inertial scale vortices, this drift effect is crucial in altering the ion vortex size. These results indicate that the KHI at Mercury-like ion-scale magnetospheric boundaries could show clear dawn-dusk asymmetries in both its linear and nonlinear growth.

show abstract

“…Such configurations occur in a variety of space plasmas, and many theoretical investigations have been performed for different regions of applications. [1][2][3][4][5][6][7][8][9][10] An extensive list of references was given, for example, by Miura. 11 One of the most prominent occurrences of the KH instability in space plasmas is at Earth's magnetopause, and hence, many of the studies focus on this topic.…”

Section: Introductionmentioning

confidence: 99%

Influence of a density increase on the evolution of the Kelvin–Helmholtz instability and vortices

et al. 2010

View full text Add to dashboard Cite

Results of two-dimensional nonlinear numerical simulations of the magnetohydrodynamic KelvinHelmholtz instability are presented. A boundary layer of a certain width is assumed, which separates the plasma in the upper layer from the plasma in the lower layer. A special focus is given on the influence of a density increase toward the lower layer. The evolution of the Kelvin-Helmholtz instability can be divided into three different phases, namely, a linear growth phase at the beginning, followed by a nonlinear phase with regular structures of the vortices, and finally, a turbulent phase with nonregular structures. The spatial scales of the vortices are about five times the initial width of the boundary layer. The considered configuration is similar to the situation around unmagnetized planets, where the solar wind ͑upper plasma layer͒ streams past the ionosphere ͑lower plasma layer͒, and thus the plasma density increases toward the planet. The evolving vortices might detach around the terminator of the planet and eventually so-called plasma clouds might be formed, through which ionospheric material can be lost. For the special case of a Venus-like planet, loss rates are estimated, which are of the order of estimated loss rates from observations at Venus.

show abstract

The structure of Kelvin–Helmholtz vortices with super-sonic flow

Cited by 14 publications

References 16 publications

MESSENGER orbital observations of large‐amplitude Kelvin‐Helmholtz waves at Mercury's magnetopause

MESSENGER orbital observations of large‐amplitude Kelvin‐Helmholtz waves at Mercury's magnetopause

Kinetic effects on the Kelvin–Helmholtz instability in ion-to-magnetohydrodynamic scale transverse velocity shear layers: Particle simulations

Influence of a density increase on the evolution of the Kelvin–Helmholtz instability and vortices

Contact Info

Product

Resources

About