Collisional Rayleigh-Taylor instability and shear-flow in equatorial Spread-F plasma

Chakrabarti, Nikhil; Lakhina, G. S.

doi:10.5194/angeo-21-1153-2003

Cited by 7 publications

(4 citation statements)

References 19 publications

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“…However, Fu et al (1986), Ronchi et al (1989), andFlaherty et al (1999) challenged this idea by pointing out the limitations of boundary value analysis, which is incomplete when applied to non-normal models like those describing sheared flows. The issue of shear flow stabilization remains contentious, and a number of recent theoretical and computational studies continue to support the idea (Hassam, 1992;Sekar and Kelley, 1998;Chakrabarti and Lakhina, 2003). Chakrabarti and Lakhina (2001) further showed that the nonlinear evolution of the Rayleigh-Taylor instability itself induces shear flow which contributes to the saturation of the instability.…”

Section: Discussionmentioning

confidence: 99%

Possible ionospheric preconditioning by shear flow leading to equatorial spread <i>F</i>

2005

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Abstract. Vertical shear in the zonal plasma drift speed is apparent in incoherent and coherent scatter radar observations of the bottomside F region ionosphere made at Jicamarca from about 1600-2200 LT. The relative importance of the factors controlling the shear, which include competition between the E and F region dynamos as well as vertical currents driven in the E and F regions at the dip equator, is presently unknown. Bottom-type scattering layers arise in strata where the neutral and plasma drifts differ widely, and periodic structuring of irregularities within the layers is telltale of intermediate-scale waves in the bottomside. These precursor waves appear to be able to seed ionospheric interchange instabilities and initiate full-blown equatorial spread F . The seed or precursor waves may be generated by a collisional shear instability. However, assessing the viability of shear instability requires measurements of the same parameters needed to understand shear flow quantitatively -thermospheric neutral wind and off-equatorial conductivity profiles.

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Section: Discussionmentioning

confidence: 99%

Possible ionospheric preconditioning by shear flow leading to equatorial spread <i>F</i>

2005

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“…Also, the CSI and GRT instabilities were treated separately and never together. Does the shear flow required by the former stabilize the latter, as linear, nonlocal theory predicts [ Guzdar et al , 1983; Satyanarayana et al , 1987; Hassam , 1992; Chakrabarti and Lakhina , 2003]? Does the former merely seed the latter?…”

Section: Introductionmentioning

confidence: 99%

Three‐dimensional numerical simulation of equatorial F region plasma irregularities with bottomside shear flow

Aveiro

Hysell

2010

J. Geophys. Res.

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[1] A three-dimensional numerical simulation of plasma density irregularities in the postsunset equatorial F region ionosphere leading to equatorial spread F (ESF) is described. The simulation advances the plasma number density and electrostatic potential forward in time by enforcing the constraints of quasi-neutrality and momentum conservation. The magnetic field lines are not modeled as equipotentials. Simulations are performed for cases with no background winds, with no background electric field or gravity, and with winds, a background electric field, and gravity all working in concert. The first run produced generalized Rayleigh Taylor (GRT) instability, and the second produced collisional shear instability (CSI). The combined run produced an instability which developed into an intense ESF event more quickly and with more realistic characteristics than the other two. Simulation results are compared with incoherent and coherent scatter radar data from the magnetic equator. A number of signature ESF characteristics are shown to be reproduced by the simulation.

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“…However, shear stabilization has been challenged by Fu et al [1986], Ronchi et al [1989], and Flaherty et al [1999], who pointed out the limitations of boundary value analyses, which neglect the so‐called transient response that can predominate in sheared flows and which overestimate the wavelength of the most unstable mode in the early stages of the flow. The issue of shear flow stabilization remains unresolved, and a number of recent theoretical and computational studies continue to support the premise [ Hassam , 1992; Sekar and Kelley , 1998; Chakrabarti and Lakhina , 2003]. Studies have also investigated the effects of shear on parallel electron dynamics important at high latitudes [e.g., Satyanarayana et al , 1987b; Shukla and Rahman , 1998] as well as the generation of kilometric plasma irregularities by parallel shear flow near auroral arcs [e.g., Basu et al , 1984; Basu and Coppi , 1988, 1989; Willig et al , 1997].…”

Section: Introductionmentioning

confidence: 99%

Collisional shear instability in the equatorial F region ionosphere

2004

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[1] A collisional shear instability in a magnetized plasma is described and evaluated. The instability is related to electrostatic Kelvin Helmholtz but operates in inhomogeneous plasmas in the collisional regime. Boundary value analysis predicts that the linear growth rate for the instability could be comparable to that of the collisional interchange instability in the equatorial F region ionosphere under ideal conditions. An initial value simulation of a nonlinear model of the instability run under realistic conditions produces growing waves with a relatively long growth time (50 min) and with an initial wavelength of about 30 km. The simulation results are consistent with recent radar observations showing large-scale plasma waves in the bottomside equatorial ionosphere at sunset prior to the onset of spread F conditions. The role of shear instability in preconditioning the F region for interchange instabilities to occur after sunset is discussed.

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Collisional Rayleigh-Taylor instability and shear-flow in equatorial Spread-F plasma

Cited by 7 publications

References 19 publications

Possible ionospheric preconditioning by shear flow leading to equatorial spread <i>F</i>

Possible ionospheric preconditioning by shear flow leading to equatorial spread <i>F</i>

Three‐dimensional numerical simulation of equatorial F region plasma irregularities with bottomside shear flow

Collisional shear instability in the equatorial F region ionosphere

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Collisional Rayleigh-Taylor instability and shear-flow in equatorial Spread-F plasma

Cited by 7 publications

References 19 publications

Possible ionospheric preconditioning by shear flow leading to equatorial spread &lt;i&gt;F&lt;/i&gt;

Possible ionospheric preconditioning by shear flow leading to equatorial spread &lt;i&gt;F&lt;/i&gt;

Three‐dimensional numerical simulation of equatorial F region plasma irregularities with bottomside shear flow

Collisional shear instability in the equatorial F region ionosphere

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Possible ionospheric preconditioning by shear flow leading to equatorial spread <i>F</i>

Possible ionospheric preconditioning by shear flow leading to equatorial spread <i>F</i>