Parallel inhomogeneous flows in a thermally anisotropic plasma: The electrostatic ion-acoustic branch

Spangler, Robert; Scime, Earl; Ganguli, G.

doi:10.1063/1.1480269

Cited by 21 publications

(39 citation statements)

References 32 publications

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“…Note that the previous dispersion relation is equivalent to the one presented by Spangler et al (2002). For the IA branch, b i 1 and, therefore, the n = 0 term dominates the series.…”

Section: Kinetic Theorymentioning

confidence: 84%

“…For the IA branch, b i 1 and, therefore, the n = 0 term dominates the series. In their analysis, Scime et al (2003), Spangler et al (2002) and Spangler (2001) reported that the k 2 λ Di⊥ term has a negligible effect on the dispersion relation solutions. We follow the same procedure and consider wavelengths much larger than the Debye radius in order to guarantee quasi-neutrality.…”

Section: Kinetic Theorymentioning

confidence: 99%

“…Later, Perron et al (2009) systematically studied the threshold solutions of St-Maurice et al (2007) kinetic dispersion relation for different ion to electron temperature ratios. Besides, the Gavrishchaka et al (1998) and Gavrishchaka et al (1999) work was extended by Spangler et al (2002) who derived a dispersion relation for a Maxwellian plasma which includes temperature anisotropy and shears. They showed that ion temperature anisotropy alters the frequency modes of the sheared CDEIA instability by solving numerically the dispersion equation.…”

Section: Introductionmentioning

confidence: 99%

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Ion temperature anisotropy effects on threshold conditions of a shear-modified current driven electrostatic ion-acoustic instability in the topside auroral ionosphere

et al. 2013

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Temperature anisotropies may be encountered in space plasmas when there is a preferred direction, for instance, a strong magnetic or electric field. In this paper, we study how ion temperature anisotropy can affect the threshold conditions of a shear-modified current driven electrostatic ion-acoustic (CDEIA) instability. In particular, this communication focuses on instabilities in the context of topside auroral F-region situations and in the limit where finite Larmor radius corrections are small. We derived a new fluid-like expression for the critical drift which depends explicitly on ion anisotropy. More importantly, for ion to electron temperature ratios typical of F-region, solutions of the kinetic dispersion relation show that ion temperature anisotropy may significantly lower the drift threshold required for instability. In some cases, a perpendicular to parallel ion temperature ratio of 2 and may reduce the relative drift required for the onset of instability by a factor of approximately 30, assuming the ion-acoustic speed of the medium remains constant. Therefore, the ion temperature anisotropy should be considered in future studies of ion-acoustic waves and instabilities in the high-latitude ionospheric F-region

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“…Note that the previous dispersion relation is equivalent to the one presented by Spangler et al (2002). For the IA branch, b i 1 and, therefore, the n = 0 term dominates the series.…”

Section: Kinetic Theorymentioning

confidence: 84%

Section: Kinetic Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Ion temperature anisotropy effects on threshold conditions of a shear-modified current driven electrostatic ion-acoustic instability in the topside auroral ionosphere

et al. 2013

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“…Therefore, according to the simulation results here and ignoring non-Maxwellian features of the particle distributions, the transient gradient in the relative magnetic field aligned drift as driven by the EIC wave has a negligible effect on the amplitude of IA oscillations. Additionally, the role of ion temperature anisotropy in the growth of shear-modified IA waves is to change the propagation direction or k z /k y , which is a critical term of Ganguli's generalized dispersion relation (Spangler et al, 2002;Teodorescu et al, 2003). As explained above, for a wide range of k z /k y values, the shear effect as part of EIC wave oscillations will be insignificant, and therefore ion temperature anisotropy needs to be addressed independently from the shear effect.…”

Section: Discussionmentioning

confidence: 99%

Enhanced ion acoustic lines due to strong ion cyclotron wave fields

Bahcivan

Cosgrove

2008

Ann. Geophys.

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Abstract. The Fast Auroral Snapshot Explorer (FAST) satellite detected intense and coherent 5-20 m electric field structures in the high-latitude topside auroral ionosphere between the altitudes of 350 km and 650 km. These electric fields appear to belong to electrostatic ion cyclotron (EIC) waves in terms of their frequency and wavelengths. Numerical simulations of the response of an electron plasma to the parallel components of these fields show that the waves are likely to excite a wave-driven parallel ion acoustic (IA) instability, through the creation of a highly non-Maxwellian electron distribution function, which when combined with the (assumed) Maxwellian ion distribution function provides inverse Landau damping. Because the counter-streaming threshold for excitation of EIC waves is well below that for excitation of IA waves (assuming Maxwellian statistics) our results suggest a possible two step mechanism for destabilization of IA waves. Combining this simulation result with the observational fact that these EIC waves share a common phenomenology with the naturally enhanced IA lines (NEIALS) observed by incoherent scatter radars, especially that they both occur near field-aligned currents, leads to the proposition that this two-step mechanism is an alternative path to NEIALS.

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“…For the strong shear limit, no field aligned current was required at all to destabilize ion-acoustic modes. This work was then extended by Scime et al (2002) to include thermal anisotropy and by Spangler et al (2002) who considered the effect of ion and electron temperature anisotropies. None of these extensions of the original study, however, included collisions, which raises the issue of their applicability to ionospheric situations.…”

Section: Introductionmentioning

confidence: 99%

Velocity shear and current driven instability in a collisional F-region

2009

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Abstract.We have studied how the presence of collisions affects the behavior of instabilities triggered by a combination of shears and parallel currents in the ionosphere under a variety of ion to electron temperature ratios. To this goal we have numerically solved a kinetic dispersion relation, using a relaxation model to describe the effects of ion and electron collisions. We have compared our solutions to expressions derived in a fluid limit which applied only to large electron to ion temperature ratios. We have limited our study to threshold conditions for the current density and the shears. We have studied how the threshold varies as a function of the wave-vector angle direction and as a function of frequency. As expected, we have found that for low frequencies and/or elevated ion to electron temperature ratios, the kinetic dispersion relation has to be used to evaluate the threshold conditions. We have also found that ion velocity shears can significantly lower the field-aligned threshold current needed to trigger the instability, especially for wave-vectors close to the perpendicular to the magnetic field. However the current density and shear requirements remain significantly higher than if collisions are neglected. Therefore, for ionospheric F-region applications, the effect of collisions should be included in the calculation of instabilities associated with horizontal shears in the vertical flow. Furthermore, in many situations of interest the kinetic solutions should be used instead of the fluid limit, in spite of the fact that the latter can be shown to produce qualitatively valid solutions.

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Parallel inhomogeneous flows in a thermally anisotropic plasma: The electrostatic ion-acoustic branch

Cited by 21 publications

References 32 publications

Ion temperature anisotropy effects on threshold conditions of a shear-modified current driven electrostatic ion-acoustic instability in the topside auroral ionosphere

Ion temperature anisotropy effects on threshold conditions of a shear-modified current driven electrostatic ion-acoustic instability in the topside auroral ionosphere

Enhanced ion acoustic lines due to strong ion cyclotron wave fields

Velocity shear and current driven instability in a collisional F-region

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