Beam effect on electromagnetic ion-cyclotron waves with general loss – cone distribution function in an anisotropic plasma-particle aspect analysis

Ahirwar, G.; Varma, P.; Tiwari, Meenakshi

doi:10.5194/angeo-25-557-2007

“…(4), (5), (6) and (9) for background plasma, (Ahirwar et al, 2006a(Ahirwar et al, , 2007Patel et al, 2011) W ||c,α = − λB 2 8π…”

Section: Energy Balancementioning

confidence: 99%

“…The perturbed density n 1 is obtained by the method outlined in reference (Ahirwar et al, 2006a(Ahirwar et al, , 2007 …”

Section: Density Perturbationsmentioning

confidence: 99%

“…Observations from Fast Auroral Snapshot (FAST) spacecraft at ∼4000 km altitude in ion beam region (Cattell et al, 1991;Ergun et al, 1998) show that these waves are electromagnetic. In past studies on EMIC instability, in auroral acceleration region have been performed by various authors (Gomberoff and Elgueta, 1991;Horne and Thorne, 1997;Ahirwar et al, 2006bAhirwar et al, , 2007. The up going ion beam are reported by the S3-3 satellite (Mozer et al, 1977) and by Polar satellite data (Mozer and Hull, 2001).…”

Section: Introductionmentioning

confidence: 99%

“…They have used the cold-plasma dispersion relation which may be inappropriate as plasma is thermalised and thermal anisotropies play a significant role. Ahirwar et al (2007) have not distinguished between the beam plasma and the background core plasma adopting the same distribution function for both the plasmas which may be inadequate for the analysis. In the present paper we have considered the hot plasma dispersion relation and have used separate distribution function for core plasma and the ion beam.…”

Section: Introductionmentioning

confidence: 99%

“…In the past Ahirwar et al (2007) have considered the effect of ion-beam velocities on EMIC waves with general loss-cone distribution function and have examine the effects of beam velocities and loss-cone distribution induces J . They have used the cold-plasma dispersion relation which may be inappropriate as plasma is thermalised and thermal anisotropies play a significant role.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Effect of ion beam on electromagnetic ion cyclotron instability in hot anisotropic plasma-particle aspect analysis

Patel

¹

,

Varma

²

,

Tiwari

³

et al. 2011

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Abstract. Using the general loss-cone distribution function electromagnetic ion cyclotron (EMIC) instability affected by up going ion beam has been studied by investigating the trajectories of charged particles. The plasma consisting of resonant and non-resonant particles has been considered. It is assumed that the resonant particles participate in energy exchange with the wave, whereas non-resonant particles support the oscillatory motion of the wave. The effect of ion beam velocity on the dispersion relation, growth rate, parallel and perpendicular resonant energy of the EMIC wave with general loss-cone distribution function in hot anisotropic plasma is described by particle aspect approach. The effect of beam anisotropy and beam density on electromagnetic ion cyclotron instabilities is investigated. Growth length is derived for EMIC waves in hot anisotropic plasma. It is found that the effect of the ion beam is to reduce the energy of transversely heated ions, whereas the thermal anisotropy of the background plasma acts as a source of free energy for the EMIC wave and enhances the growth rate. It is observed that ion beam velocity opposite to the wave propagation and its density reduces the growth rate and enhance the reduction in perpendicularly heated ions energy. The effect of ion beam anisotropy on EMIC wave is also discussed. These results are determined for auroral acceleration region. It is also found that the EMIC wave emissions occur by extracting energy of perpendicularly heated ions in the presence of an up flowing ion beam.

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Generation of turbulence in Kelvin-Helmholtz vortices at the Earth's magnetopause: Magnetospheric Multiscale observations

Hasegawa

¹

,

Nakamura²,

Gershman

³

et al. 2019

Preprint

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The Kelvin-Helmholtz instability (KHI) at Earth's magnetopause and associated turbulence are suggested to play a role in the transport of mass and momentum from the solar wind into Earth's magnetosphere. We investigate electromagnetic turbulence observed in Kelvin-Helmholtz vortices encountered at the dusk flank magnetopause by the Magnetospheric Multiscale (MMS) spacecraft under northward interplanetary magnetic field (IMF) conditions in order to reveal its generation process, mode properties, and role. A comparison with another MMS event at the dayside magnetopause with reconnection but no KHI signatures under a similar IMF condition indicates that while high-latitude magnetopause reconnection excites a modest level of turbulence in the dayside low-latitude boundary layer, the KHI further amplifies the turbulence, leading to magnetic energy spectra with a power law index −5/3 at magnetohydrodynamic scales even in its early nonlinear phase. The mode of the electromagnetic turbulence is analyzed with a single-spacecraft method based on Ampère's law, developed by Bellan (2016, https://doi. org/10.1002/2016JA022827), for estimating wave vectors as a function of spacecraft frame frequency. The results suggest that the turbulence does not consist of propagating normal-mode waves but is due to interlaced magnetic flux tubes advected by plasma flows in the vortices. The turbulence at sub-ion scales in the early nonlinear phase of the KHI may not be the cause of the plasma transport across the magnetopause but rather a consequence of three-dimensional vortex-induced reconnection, the process that can cause an efficient transport by producing tangled reconnected field lines. Plain Language SummaryTurbulence is ubiquitous in nature and plays an important role in material mixing and energy transport. Turbulence in space plasmas is characterized by fluctuations of flow velocity and/or electromagnetic fields over a broad frequency range and/or length scales and is believed to be the key to efficient plasma transport and heating. However, its generation mechanism is not fully understood because turbulence in space is often fully developed or already relaxed when observed. By analyzing high-resolution plasma and electromagnetic field data taken by the Magnetospheric Multiscale spacecraft, we study the generation process of electromagnetic turbulence at the outer boundary of Earth's magnetosphere, called the magnetopause, where either a flow shear-driven Kelvin-Helmholtz instability or magnetic reconnection or both could drive turbulence. It is shown that while dayside reconnection generates a modest level of turbulence at the magnetopause near noon, the flow shear instability further amplifies the turbulence at the flank magnetopause. Our analysis also suggests that the turbulence may not be the primary cause of plasma transport from solar wind into the magnetosphere but rather a consequence of the flow shear-induced reconnection that is likely the primary cause of plasma transport at the dayside flank under northward solar wi...

show abstract

Generation of turbulence in Kelvin-Helmholtz vortices at the Earth's magnetopause: Magnetospheric Multiscale observations

Hasegawa

¹

,

Nakamura²,

Gershman

³

et al. 2020

Preprint

View full text Add to dashboard Cite

The Kelvin-Helmholtz instability (KHI) at Earth's magnetopause and associated turbulence are suggested to play a role in the transport of mass and momentum from the solar wind into Earth's magnetosphere. We investigate electromagnetic turbulence observed in Kelvin-Helmholtz vortices encountered at the dusk flank magnetopause by the Magnetospheric Multiscale (MMS) spacecraft under northward interplanetary magnetic field (IMF) conditions in order to reveal its generation process, mode properties, and role. A comparison with another MMS event at the dayside magnetopause with reconnection but no KHI signatures under a similar IMF condition indicates that while high-latitude magnetopause reconnection excites a modest level of turbulence in the dayside low-latitude boundary layer, the KHI further amplifies the turbulence, leading to magnetic energy spectra with a power law index −5/3 at magnetohydrodynamic scales even in its early nonlinear phase. The mode of the electromagnetic turbulence is analyzed with a single-spacecraft method based on Ampère's law, developed by Bellan (2016, https://doi. org/10.1002/2016JA022827), for estimating wave vectors as a function of spacecraft frame frequency. The results suggest that the turbulence does not consist of propagating normal-mode waves but is due to interlaced magnetic flux tubes advected by plasma flows in the vortices. The turbulence at sub-ion scales in the early nonlinear phase of the KHI may not be the cause of the plasma transport across the magnetopause but rather a consequence of three-dimensional vortex-induced reconnection, the process that can cause an efficient transport by producing tangled reconnected field lines. Plain Language SummaryTurbulence is ubiquitous in nature and plays an important role in material mixing and energy transport. Turbulence in space plasmas is characterized by fluctuations of flow velocity and/or electromagnetic fields over a broad frequency range and/or length scales and is believed to be the key to efficient plasma transport and heating. However, its generation mechanism is not fully understood because turbulence in space is often fully developed or already relaxed when observed. By analyzing high-resolution plasma and electromagnetic field data taken by the Magnetospheric Multiscale spacecraft, we study the generation process of electromagnetic turbulence at the outer boundary of Earth's magnetosphere, called the magnetopause, where either a flow shear-driven Kelvin-Helmholtz instability or magnetic reconnection or both could drive turbulence. It is shown that while dayside reconnection generates a modest level of turbulence at the magnetopause near noon, the flow shear instability further amplifies the turbulence at the flank magnetopause. Our analysis also suggests that the turbulence may not be the primary cause of plasma transport from solar wind into the magnetosphere but rather a consequence of the flow shear-induced reconnection that is likely the primary cause of plasma transport at the dayside flank under northward solar wi...

show abstract

Beam effect on electromagnetic ion-cyclotron waves with general loss – cone distribution function in an anisotropic plasma-particle aspect analysis

Cited by 18 publications

References 60 publications

Effect of ion beam on electromagnetic ion cyclotron instability in hot anisotropic plasma-particle aspect analysis

Effect of ion beam on electromagnetic ion cyclotron instability in hot anisotropic plasma-particle aspect analysis

Generation of turbulence in Kelvin-Helmholtz vortices at the Earth's magnetopause: Magnetospheric Multiscale observations

Generation of turbulence in Kelvin-Helmholtz vortices at the Earth's magnetopause: Magnetospheric Multiscale observations

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