Concerning a problem on the Kelvin‐Helmholtz stability of the thin magnetopause

Gratton, F. T.; Bender, L.; Farrugia, Charles J.; Gnavi, G.

doi:10.1029/2003ja010146

Cited by 20 publications

(28 citation statements)

References 17 publications

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“…Theoretically, the KHI grows when the shear flow is larger than a certain threshold according to a linear inequality [ Hasegawa , ; Gratton et al , ]:

{(boldV \cdot boldk)}^{2} \geq \frac{ρ_{1} + ρ_{2}}{μ ρ_{1} ρ_{2}} ([], {(bold B_{1} \cdot boldk)}^{2} + {(bold B_{2} \cdot boldk)}^{2})

where k is the wave vector. V , B , and ρ denote the velocity difference between the two plasma, magnetic field, and total mass density.…”

Section: Discussionmentioning

confidence: 99%

Exploring the influence of ionospheric O⁺ outflow on magnetospheric dynamics: The effect of outflow intensity

Ridley

2013

JGR Space Physics

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[1] The ionospheric O + outflow varies dramatically during geomagnetic activities, but the influence of its initial characteristics on the magnetospheric dynamics has not been well established. To expand a previous study on the impact of ionospheric heavy ions outflow originating from different source regions on the magnetotail dynamics and dayside reconnection rate, this study conducts two idealized numerical experiments with different O + outflow densities to examine the consequent change in the magnetosphere system, especially on the solar wind-magnetosphere coupling efficiency. Results indicate that a larger O + outflow is capable of triggering the Kelvin-Helmholtz instability (KHI) on the magnetopause flanks. The subsequent surface waves enhance the solar wind-magnetosphere coupling efficiency by transmitting more solar wind energy into the magnetosphere-ionosphere system, increasing the cross polar cap potential index. This index is initially reduced after the ionospheric mass loading owing to the direct depression in the dayside reconnection rate as commonly reported from earlier literature. The above KHI is generated under steady state solar wind conditions, suggesting that besides the commonly recognized cause, the elevated solar wind speed, ionospheric heavy ions outflow is another potential factor in disturbing the boundary by enhancing the mass density near the magnetopause and thus lowering the threshold for generating KHI. During storms, the increased ionospheric mass source causes an increased probability of KHI, which allows more solar wind plasma into the magnetosphere. This implies there is a possibility of even further nonlinear coupling between the magnetosphere and solar wind.

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“…Theoretically, the KHI grows when the shear flow is larger than a certain threshold according to a linear inequality [ Hasegawa , ; Gratton et al , ]:

{(boldV \cdot boldk)}^{2} \geq \frac{ρ_{1} + ρ_{2}}{μ ρ_{1} ρ_{2}} ([], {(bold B_{1} \cdot boldk)}^{2} + {(bold B_{2} \cdot boldk)}^{2})

where k is the wave vector. V , B , and ρ denote the velocity difference between the two plasma, magnetic field, and total mass density.…”

Section: Discussionmentioning

confidence: 99%

Exploring the influence of ionospheric O⁺ outflow on magnetospheric dynamics: The effect of outflow intensity

Ridley

2013

JGR Space Physics

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“…where the subscripts 1 and 2 are defined to represent the magnetosheath and magnetosphere sides, respectively (note, however, that the above condition, derived for an infinitesimally thin shear layer, can be relaxed when the shear layer has a non-zero thickness (Gratton et al, 2004)). For ρ 2 ρ 1 , (ρ 1 + ρ 2 )/ρ 1 ρ 2 = (1 + ρ 2 /ρ 1 )/ρ 2 ∼ 1/ρ 2 , so it can be said that inequality (15) becomes more easily satisfied with increasing density ρ 2 on the magnetosphere side, i.e., the KHI can be excited thanks to the presence of the dense LLBL.…”

Section: Excitation Of the Kelvin-helmholtz Instabilitymentioning

confidence: 99%

Structure and Dynamics of the Magnetopause and Its Boundary Layers

Hasegawa¹

2012

Monogr. Environ. Earth Planets

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The magnetopause is the key region in space for the transfer of solar wind mass, momentum, and energy into the magnetosphere. During the last decade, our understanding of the structure and dynamics of Earth's magnetopause and its boundary layers has advanced considerably, thanks largely to the advent of multi-spacecraft missions such as Cluster and THEMIS. Moreover, various types of physics-based techniques have been developed for visualizing two-or threedimensional plasma and field structures from data taken by one or more spacecraft, providing a new approach to the analysis of the spatiotemporal properties of magnetopause processes, such as magnetic reconnection and the Kelvin-Helmholtz instability (KHI). Information on the size, shape, orientation, and evolution of magnetic flux ropes or flow vortices generated by those processes can be extracted from in situ measurements. Observations show that magnetopause reconnection can be globally continuous for both southward and northward interplanetary magnetic field (IMF) conditions, but even under such circumstances, more than one X-line may exist within a certain (low-latitude or high-latitude) portion on the magnetopause and some X-lines may retreat anti-sunward. The potential global effects of such behavior are discussed. An overview is also given of the identification, excitation, evolution, and possible consequences of the magnetopause KHI: there is evidence for nonlinear KHI growth and associated vortex-induced reconnection under northward IMF. Observation-based estimates indicate that reconnection tailward of both polar cusps can be the dominant mechanism for solar wind plasma entry into the dayside magnetosphere under northward IMF. However, the mechanism by which the transferred plasma is transported into the central portion of the magnetotail, and the role of magnetopause processes in this transport, remain unclear. Future prospects of magnetopause and other relevant studies are also discussed.

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“…How does the broadening of the flank BL produced by the KH instability depend on (i) the local orientation of B and V; (ii) the physical conditions at the boundary; and (iii) its distance from the subsolar point? Some of these questions have been addressed by members of our team, and by coworkers in recent studies [1,23,24,26,27,28,29,30].…”

Section: The Aims Of This Workmentioning

confidence: 99%

“…In 1984, Miura [31] initiated the computational studies of KH in the MP context. Since then, the steady progress in this area can be appraised in a set of reviews (for instance [32,33,34,14]), and in recent research papers (among others: [1,12,13,15,16,17,18,19,20,22,23,24]). We base the large eddy simulations (LES) on non-dissipative, compressible, MHD equations in 3D and time.…”

Section: Les and Computational Codementioning

confidence: 99%

The Magnetosphere Mixing Layer: Observations, MHD Stability, and Large Eddy Simulations

Gratton

Bilbao

Gnavi

et al. 2011

J. Phys.: Conf. Ser.

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Abstract.The work is about the evolution of large vortices in the boundary layer of the terrestrial magnetopause studied by computational physics, in support of interpretive analysis of spacecraft data from an event observed on December 7, 2000. The distinctive features of the configuration examined are i) the very small magnetic shear across the boundary, and ii) the dynamics concerns mainly the vorticity. The magnetic field is only fluted during the process, but it determines the direction of the vortex axis. Considering new elements from computer simulations and observations, an extension of the research of a recent publication in this journal is reported. A magnetohydrodynamic code for large eddy simulations is used to examine the influence of supersonic, and superAlfvénic speeds, on the dynamics of the boundary layer. Correlations of data are studied to identify signatures of the Kelvin-Helmholtz instability, and the presence of whirling plasma. The aim is to improve the understanding of factors that govern the tailward growth of the low latitude boundary layer, and the potentiality of plasma entry into the magnetosphere, during periods of northward interplanetary magnetic field.

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Concerning a problem on the Kelvin‐Helmholtz stability of the thin magnetopause

Cited by 20 publications

References 17 publications

Exploring the influence of ionospheric O⁺ outflow on magnetospheric dynamics: The effect of outflow intensity

Exploring the influence of ionospheric O⁺ outflow on magnetospheric dynamics: The effect of outflow intensity

Structure and Dynamics of the Magnetopause and Its Boundary Layers

The Magnetosphere Mixing Layer: Observations, MHD Stability, and Large Eddy Simulations

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Concerning a problem on the Kelvin‐Helmholtz stability of the thin magnetopause

Cited by 20 publications

References 17 publications

Exploring the influence of ionospheric O+ outflow on magnetospheric dynamics: The effect of outflow intensity

Exploring the influence of ionospheric O+ outflow on magnetospheric dynamics: The effect of outflow intensity

Structure and Dynamics of the Magnetopause and Its Boundary Layers

The Magnetosphere Mixing Layer: Observations, MHD Stability, and Large Eddy Simulations

Contact Info

Product

Resources

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Exploring the influence of ionospheric O⁺ outflow on magnetospheric dynamics: The effect of outflow intensity

Exploring the influence of ionospheric O⁺ outflow on magnetospheric dynamics: The effect of outflow intensity