Modeling the dominance of the gradient drift or Kelvin–Helmholtz instability in sheared ionospheric E × B flows

Rathod, Chirag; Srinivasan, Bhuvana; Scales, W. A.

doi:10.1063/5.0047807

Cited by 6 publications

(3 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The plasma loss creates the density trough, and the steep density gradient can be a source of the plasma instability. For weaker and latitudinally broader SAPS flows, the trough density gradient has been shown to create density irregularities through the gradient drift instability and Kelvin−Helmholtz instability (Rathod et al, 2021). Steeper density and velocity gradients for intense SAID may create an even stronger instability.…”

Section: Chemistry and Emission Mechanismsmentioning

confidence: 99%

Unsolved problems in Strong Thermal Emission Velocity Enhancement (STEVE) and the picket fence

Nishimura

Dyer

Kangas³

et al. 2023

Front. Astron. Space Sci.

View full text Add to dashboard Cite

This paper reviews key properties and major unsolved problems about Strong Thermal Emission Velocity Enhancement (STEVE) and the picket fence. We first introduce the basic characteristics of STEVE and historical observations of STEVE-like emissions, particularly the case on 11 September 1891. Then, we discuss major open questions about STEVE: 1) Why does STEVE preferentially occur in equinoxes? 2) How do the solar wind and storm/substorm conditions control STEVE? 3) Why is STEVE rare, despite that STEVE does not seem to require extreme driving conditions? 4) What are the multi-scale structures of STEVE? 5) What mechanisms determine the properties of the picket fence? 6) What are the chemistry and emission mechanisms of STEVE? 7) What are the impacts of STEVE on the ionosphere−thermosphere system? Also, 8) what is the relation between STEVE, stable auroral red (SAR) arcs, and the subauroral proton aurora? These issues largely concern how STEVE is created as a unique mode of response of the subauroral magnetosphere−ionosphere−thermosphere coupling system. STEVE, SAR arcs, and proton auroras, the three major types of subauroral emissions, require energetic particle injections to the pre-midnight inner magnetosphere and interaction with cold plasma. However, it is not understood why they occur at different times and why they can co-exist and transition from one to another. Strong electron injections into the pre-midnight sector are suggested to be important for driving intense subauroral ion drifts (SAID). A system-level understanding of how the magnetosphere creates distinct injection features, drives subauroral flows, and disturbs the thermosphere to create optical emissions is required to address the key questions about STEVE. The ionosphere−thermosphere modeling that considers the extreme velocity and heating should be conducted to answer what chemical and dynamical processes occur and how much the STEVE luminosity can be explained. Citizen scientist photographs and scientific instruments reveal the evolution of fine-scale structures of STEVE and their connection to the picket fence. Photographs also show the undulation of STEVE and the localized picket fence. High-resolution observations are required to resolve fine-scale structures of STEVE and the picket fence, and such observations are important to understand underlying processes in the ionosphere and thermosphere.

show abstract

Section: Chemistry and Emission Mechanismsmentioning

confidence: 99%

Unsolved problems in Strong Thermal Emission Velocity Enhancement (STEVE) and the picket fence

Nishimura

Dyer

Kangas³

et al. 2023

Front. Astron. Space Sci.

View full text Add to dashboard Cite

show abstract

“…The behavior of this phenomenon is typical of two-dimensional turbulence [82], especially for the Kelvin-Helmholtz type fluid instability [83]. In this context, the origin of the instability may be associated with drift velocity differences across the cathode plasma.…”

Section: Plasma Oscillationsmentioning

confidence: 97%

On a force balance and role of cathode plasma in Hall effect thrusters

Chernyshev¹,

Krivoruchko²

2022

Plasma Sources Sci. Technol.

View full text Add to dashboard Cite

The cathode plasma is a specific transition region in the Hall Effect Thruster (HET) discharge that localizes between the strongly magnetized acceleration layer (magnetic layer or B-layer) and non-magnetized exhaust plume. Cathode plasma provides a flow of electron current that supplies losses in the magnetic layer (due to ionization, excitation, electron-wall interactions, etc.). The electrons' transport in this region occurs in collisionless mode through the excitation of plasma instabilities. This effect is also known as "anomalous transport/conductivity". In this work, we present the results of a 2d (drift-plane) kinetic simulation of the HET discharge, including the outside region that contains cathode plasma. We discuss the process of cathode plasma formation and the mechanisms of "anomalous transport" inside it. We also analyze how fluid force balance emerges from collisionless kinetic approach. The acceleration mechanism in Hall Effect Thrusters (HETs) is commonly described in terms of force balance. Namely, the reactive force produced by accelerated ions has the same value as Ampère's force acting on a drift current loop. This balance written in integral form provides the basis for quantitative estimations of HETs' parameters and scaling models.

show abstract

“…Therefore, the charge exchange between the ions and neutrals will generate a drag force that decreases the strength of the sheared E × B flow. Previous studies (Keskinen et al 1988;Khomenko 2016;Rathod et al 2021) have reported that the electrostatic KHI can be damped by collisions and that ion-neutral interactions can lead to a modification of the onset criteria and the growth rates of KHI and Rayleigh-Taylor instability (RTI) encountered in chromospheric heating solar plasmas. Thus, the effect of ionneutral collisions on the sheared E × B flow and the accompanying plasma instabilities in the ion cyclotron frequency range has been investigated in order to interpret the dynamical processes in partially ionized plasma such as the solar chromosphere and planetary ionosphere in this work.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of the Response of Sheared E × B Flow to Varying Ion–Neutral Collisions

Zhang,

Liu,

Lei

et al. 2023

ApJ

View full text Add to dashboard Cite

Partially ionized plasma is a common occurrence in astrophysical and space environments. The emergence and development of plasma instabilities are significantly impacted by the inelastic collisions between the ions and neutrals in the partially ionized plasma, such as the charge exchange. In this study, the effect of the ion–neutral collisions on the sheared E × B flow was experimentally investigated. In the weak collision range, the shear-driven plasma instability, such as Kelvin–Helmholtz instability, was excited by the velocity-sheared flow. However, increasing ion–neutral collisions resulted in a decrease in the magnitude of the sheared E × B flow due to charge exchange–induced drag forces. Consequently, the Kelvin–Helmholtz instability is suppressed, and the Rayleigh–Taylor instability is triggered. The underlying mechanism was elucidated through experimental findings and numerical analysis. The result of this study proposes that a transition between the two modes occurred with increasing ion–neutral collision strength. It could be applied to the study of the solar chromosphere and prominence and planetary ionospheres, where plasma is partially ionized and the sheared E × B flow is often encountered.

show abstract

Modeling the dominance of the gradient drift or Kelvin–Helmholtz instability in sheared ionospheric E × B flows

Cited by 6 publications

References 47 publications

Unsolved problems in Strong Thermal Emission Velocity Enhancement (STEVE) and the picket fence

Unsolved problems in Strong Thermal Emission Velocity Enhancement (STEVE) and the picket fence

On a force balance and role of cathode plasma in Hall effect thrusters

Experimental Study of the Response of Sheared E × B Flow to Varying Ion–Neutral Collisions

Contact Info

Product

Resources

About