Coherent structure generated in the boundary layer of a laboratory‐created ionospheric depletion

Liu, Yu; Cao, Jinxiang; Xu, Liukang; Zhang, Xiao; Wang, Pi; Wang, Jian; Du, Yinchang; Zheng, Zhe

doi:10.1002/2014gl059211

Cited by 16 publications

(7 citation statements)

References 31 publications

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“…The sheared flow has been frequently observed by satellites and rockets in solar‐terrestrial space plasmas (Ganguli et al, ; Miura, , ; Moore et al, ; Paschmann et al, ; Sundkvist et al, ), and it is widely taken as a dominant source of free energy for the excitation of the electrostatic and electromagnetic instability in a broadband frequency range (Amatucci, ; DuBois, Thomas Jr, et al, ; Ganguli et al, ; Liu et al, ; Liu et al, ; Tejero et al, ). The Kelvin‐Helmholtz instability (KHI) is one of the shear‐driven modes (Peñano & Ganguli, ), and it is frequently observed in the solar corona, solar wind, magnetopause, inner magnetosphere, and ionosphere of the Earth, planets, and comets (Fairfield et al, ; Johnson et al, ; Nykyri & Otto, ; Phan & Paschmann, ; Soler et al, ; Terada et al, ).…”

Section: Introductionmentioning

confidence: 99%

Laboratory Excitation of the Kelvin‐Helmholtz Instability in an Ionospheric‐Like Plasma

Liu

Lei

et al. 2018

Geophysical Research Letters

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In the work, laboratory experiments were designed to simulate the collisional plasma environment of the ionosphere. Neutral gas was injected to increase the ion-neutral collisions, and the ambient plasma subsequently transforms from the magnetospheric-like collisionless plasma to the ionospheric-like collisional one. In the collisionless plasma, the classical electrostatic Kelvin-Helmholtz instability (KHI) was generated using an interpenetrating plasma method. However, the collisionless KHI was dissipated in the collisional plasma and subsequently a new wave mode was excited. The mode was identified as the collisional KHI by comparing the experimental results with the theoretical wave dispersion relation. The result indicates that the KHI can be excited in the ionospheric-like collisional plasma, which could be applied to understand the generation mechanism of the ionospheric irregularities by the bottomside sheared flow.Plain Language Summary Ionospheric irregularities, in the form of density spikes and cavities, are universal in the ionosphere from low to high latitudes. The ionospheric irregularities have a significant impact on satellite radio communications. The Kelvin-Helmholtz instability (KHI) was considered to play a significant role in the generation of the ionospheric irregularities. However, a key issue is that the generation of KHI in a collisional plasma has not been experimentally verified. In the work, laboratory experiments were conducted to simulate the collisional environment of the ionosphere. The result suggests that the shear-driven KHIs can be generated in an ionospheric-like collisional plasma. Through our experimental work, the theoretical mechanism can be more confidently applied to explain the excitation of ionospheric irregularities.

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Section: Introductionmentioning

confidence: 99%

Laboratory Excitation of the Kelvin‐Helmholtz Instability in an Ionospheric‐Like Plasma

Liu

Lei

et al. 2018

Geophysical Research Letters

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“…In the experiment, the density, potential, and magnetic field all were disturbed by the velocity shear (see Figure S2 of supporting information). The time‐sampled data were transformed into the frequency domain via fast Fourier transform to obtain the auto power spectrum density (PSD) and cross‐power spectrum density (CSD) (Liu et al, ; Kim & Powers, ; Smith et al, ). Figure a shows the spectral information of these shear‐driven density and potential fluctuations.…”

Section: Resultsmentioning

confidence: 99%

Spontaneous Emission of Alfvénic Branch Oscillations From a Strong Inhomogeneous Plasma Flow

Liu

Lei

et al. 2018

Geophysical Research Letters

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Laboratory observations of spontaneous emission of Alfvénic branch oscillations generated by a strong inhomogeneous plasma flow are reported in this work. Electrostatic KH instabilities in the subcyclotron frequency range were excited using the interpenetrating plasma method. Experiments indicate that spontanegeous Alfvénic branch oscillations occur when the plasma inhomogeneity increases above a threshold. The electromagnetic wave amplitude spreads out radially over a much larger extent than the electrostatic mode. Theoretical calculations using the MHD method also support the experimental observation. The result has important application in understanding the cross‐scale transport of particles and energies in astrophysical, space, and laboratory plasmas.

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“…Specifically, the electron-ion hybrid (EIH) instability is driven by the transverse velocity shear with intermediate scale length ( e < L E < i ), when ions are effectively unmagnetized and electrons have shear corrected velocity distributions (e.g., Ganguli et al, 1988aGanguli et al, , 1988bRomero et al, 1992). The kinetic EIH modes have been verified in a number of space and laboratory experiments and numerical simulations (e.g., Amatucci et al, 1996;DuBois et al, 2014;Liu et al, 2014Liu et al, , 2017Romero & Ganguli, 1993;Scales, Bernhardt, Ganguli, Siefring, & Rodriguez, 1994) and are suggested to be important mechanisms for the generation of broadband electrostatic fluctuations. However, previous EIH studies have been mostly focused on the electrostatic emissions and assumed uniform magnetic field for simplicity (e.g., Romero & Ganguli, 1993;Romero et al, 1992).…”

Section: Introductionmentioning

confidence: 90%

A New Perspective for Dipolarization Front Dynamics: Electromagnetic Effects of Velocity Inhomogeneity

et al. 2019

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The stability of a quasi‐static near‐Earth dipolarization front (DF) is investigated with a two‐dimensional electromagnetic particle‐in‐cell model. Strongly localized ambipolar electric fields self‐consistently generate a highly sheared dawnward trueE→×trueB→ electron drift on the kinetic scale in the DF. Electromagnetic particle‐in‐cell simulations based on the observed DF thickness and gradients of plasma/magnetic field parameters reveal that the DF is susceptible to the kinetic electron‐ion hybrid (EIH) instability driven by the strong velocity inhomogeneity. The excited waves show a broadband spectrum in the lower hybrid (LH) frequency range, which has been often observed at DFs. The wavelength is comparable to the shear scale length, and the growth rate is also in the LH frequency range, which are consistent with the EIH theory. As a result of the LH wave emissions, the velocity shear is relaxed, and the DF is broadened. When the plasma beta increases, the wave mode shifts to longer wavelengths with reduced growth rates and enhanced magnetic fluctuations although the wave power is mostly in the electrostatic regime. This study highlights the role of velocity inhomogeneity in the dynamics of DF which has been long neglected. The EIH instability is suggested to be an important mechanism for the wave emissions and steady‐state structure at the DF.

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Coherent structure generated in the boundary layer of a laboratory‐created ionospheric depletion

Cited by 16 publications

References 31 publications

Laboratory Excitation of the Kelvin‐Helmholtz Instability in an Ionospheric‐Like Plasma

Laboratory Excitation of the Kelvin‐Helmholtz Instability in an Ionospheric‐Like Plasma

Spontaneous Emission of Alfvénic Branch Oscillations From a Strong Inhomogeneous Plasma Flow

A New Perspective for Dipolarization Front Dynamics: Electromagnetic Effects of Velocity Inhomogeneity

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