Charts of joint Kelvin‐Helmholtz and Rayleigh‐Taylor instabilites at the dayside magnetopause for strongly northward interplanetary magnetic field

Farrugia, C. J.; Gratton, F. T.; Bender, L.; Biernat, H. K.; Еркаев, Н. В.; Quinn, J. M.; Torbert, R. B.; Dennisenko, V.

doi:10.1029/97ja03248

Cited by 76 publications

(108 citation statements)

References 31 publications

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“…A derivation of the equation that governs the mode amplitude ζ(y) (omitted here for brevity) can be found, for instance, in Farrugia et al [7]. The equation is d dy…”

Section: The Basic Equation Of the Mhdmentioning

confidence: 99%

On the MHD boundary of Kelvin-Helmholtz stability diagram at large wavelengths

Gratton

Gnavi

Farrugia³

et al. 2004

Braz. J. Phys.

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Working within the domain of inviscid incompressible MHD theory, we found that a tangential discontinuity (TD) separating two uniform regions of different density, velocity and magnetic field may be Kelvin-Helmholtz (KH) stable and yet a study of a transition between the same constant regions given by a continuous velocity profile shows the presence of the instability with significant growth rates. Since the cause of the instability stems from the velocity gradient, and since a TD may be considered as the ultimate limit of such gradient, the statement comes as a surprise. In fact, a long wavelength (λ) boundary for the KH instability does not exist in ordinary liquids being instead a consequence of the presence of magnetic shear, a possibility that has passed unnoticed in the literature. It is shown that KH modes of a magnetic field configuration with constant direction do not have the long λ boundary. A theoretical explanation of this feature and examples of the violation of the TD stability condition are given using a model that can be solved in closed form. Stability diagrams in the (kd, MA) plane are given (where kd = 2πd/λ, 2d is the velocity gradient length scale, and MA is the Alfvénic Mach number) that show both the well-known limit at small λs and the boundary for large but finite λs noted here. Consequences of this issue are relevant for stability studies of the dayside magnetopause as the stability condition for a TD should be used with care in data analysis work.

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“…A derivation of the equation that governs the mode amplitude ζ(y) (omitted here for brevity) can be found, for instance, in Farrugia et al [7]. The equation is d dy…”

Section: The Basic Equation Of the Mhdmentioning

confidence: 99%

On the MHD boundary of Kelvin-Helmholtz stability diagram at large wavelengths

Gratton

Gnavi

Farrugia³

et al. 2004

Braz. J. Phys.

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“…However, the most favorable region in space for its multipoint in-situ observation and analysis is by far the outer boundary of the Earth's magnetosphere -the magnetopause -and its adjacent boundary layers [e.g. 2,3,4].…”

Section: Introductionmentioning

confidence: 99%

“…The size of this KH unstable domain may set an upper limit for the KH wavelength [2,4]. Figure 1 illustrates the relation between the regions satisfying the conditions for the KH instability onset, i.e.…”

mentioning

confidence: 99%

“…As the clock angle increases in absolute value (the case of negative clock angle is represented in Figure 1b), the regions of instability narrow and migrate away from the equator, southward on one flank and northward on the other, depending on the sign of the clock angle. Recent 3-D numerical simulations [16] show strong reconnection processes at the boundaries of the KH unstable domain, strongly enhanced plasma transport and, critically, the impact of the 3-D geometry on the wavelength of unstable modes, such that can be unveiled by changes in IMF clock angle [2,4]. Arguably, a key factor controlling the wavelengths, λ , is the distance of the observing site from the subsolar point, because the magnetosheath flow speed picks up as one moves tailward, leading to a λ -stretching effect.…”

mentioning

confidence: 99%

“…wave activity generation, and the IMF clock angle, defined as the polar angle of the IMF direction in the Geocentric Solar Magnetospheric (GSM) YZ plane. This figure is adapted from [2], who performed linear MHD simulations of the incompressible surface mode disturbances on a mesh covering the dayside of a model magnetopause. Regions of maximum KH growth rates on the dayside magnetopause correspond, as expected, to regions of high flow shear and low magnetic shear.…”

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confidence: 99%

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Kelvin-Helmholtz Multi-Spacecraft Studies at the Earth’s Magnetopause Boundaries

Foullon¹,

Farrugia²,

Owen³

et al. 2010

AIP Conference Proceedings

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Abstract. The Kelvin-Helmholtz (KH) instability can operate in various situations in the solar wind, but at the boundaries of planetary obstacles, for example the Earth's magnetopause, it is most amenable to investigation. Reliable estimates of wave characteristics are essential for comparison with theoretical and numerical models and for understanding the nonlinear development of KH waves and their role in the plasma entry into the magnetosphere. After discussing their typical conditions of appearance in KH unstable domains at the magnetopause, both theoretically and observationally, we outline recent results of multi-spacecraft analysis with Cluster giving accurate, albeit spatially limited, determination of surface wave characteristics. Those characteristics (wavelength and propagation direction), close to the terminator on the nightside, are likely to be prescribed by the 3-D geometry and the bending of field lines developed by the KH waves, rather than by the magnitude and the direction of the magnetosheath or background flow. An unprecedented number of satellites provides now the opportunity to extend the analysis of source regions of KH waves and their domains of development.

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Properties of Kelvin‐Helmholtz waves at the magnetopause under northward interplanetary magnetic field: Statistical study

Lin

Wang

et al. 2014

JGR Space Physics

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We search the plasma and magnetic field data of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes B and C during 2008 and 2009 for observation evidences of the Kelvin‐Helmholtz instability (KHI). Fourteen KHI events with rolled‐up vortices are identified under the northward interplanetary magnetic field (IMF) at the low‐latitude boundary layer (LLBL). We collect another 42 events reported from the observations of the Geotail, Double Star TC‐1, and Cluster for a statistical study of the KH wave properties. All the 56 rolled‐up KH wave events are quantitatively characterized by the dominant period, phase velocity, and the wavelength. We further explore the relationship between the KH wave period and the solar wind velocity (VSW) and the IMF clock angle. It is found that the KH period tends to be shorter under a higher VSW, and longer with a larger IMF clock angle. The spatial distribution of the KH wavelength shows a longitudinal growth with increasing distance from the subsolar point along the flank magnetopause. The statistical results provide new insights for the development of KH waves and their connection with the interplanetary conditions and deepen our understanding of the KHI at the magnetopause.

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Charts of joint Kelvin‐Helmholtz and Rayleigh‐Taylor instabilites at the dayside magnetopause for strongly northward interplanetary magnetic field

Cited by 76 publications

References 31 publications

On the MHD boundary of Kelvin-Helmholtz stability diagram at large wavelengths

On the MHD boundary of Kelvin-Helmholtz stability diagram at large wavelengths

Kelvin-Helmholtz Multi-Spacecraft Studies at the Earth’s Magnetopause Boundaries

Properties of Kelvin‐Helmholtz waves at the magnetopause under northward interplanetary magnetic field: Statistical study

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