A Time‐Dependent Two‐Dimensional Model Simulation of Lower Ionospheric Variations Under Intense SAID

Liang, J.; St.-Maurice, J.-P.; Donovan, E.

doi:10.1029/2021ja029756

Cited by 16 publications

(38 citation statements)

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“…SAID's have been investigated in both ground and space‐based observations (e.g., Anderson et al., 1991, 1993, 2001; Archer & Knudsen, 2018; Foster et al., 1994; Karlsson et al., 1998; He et al., 2014; Mishin, 2013; Puhl‐Quinn et al., 2007). Motivated by the observations, numerous models have been constructed to study the ionospheric processes (e.g., Heelis et al., 1993; Liang et al., 2021; Moffett et al., 1992, 1998) and magnetospheric processes (Nishimura, Yang, et al., 2020; Wang et al., 2021) involved with SAID. SAID shares some similar properties with, yet differ in a few key aspects from, another subauroral flow phenomenon called the “subauroral polarisation streams” (SAPS), which is usually weaker in flow magnitude and broader in latitudinal width than SAID (e.g., Foster & Burke, 2002; Mishin et al., 2017].…”

Section: Introductionmentioning

confidence: 99%

“…Recently, Liang et al. (2021) (hereafter referred to as LJ21) presented a comprehensive and dedicated study on the role of ion Pedersen transport in the dynamic variations of the lower ionosphere in a SAID channel. Using a two‐dimensional (2D) time‐dependent model tailored to SAID conditions, LJ21 found that the transport effect of ion Pedersen drifts leads to strong density depletion and conductance drop in the lower ionosphere over a large portion of SAID.…”

Section: Introductionmentioning

confidence: 99%

“…The role of ion Pedersen transport in the plasma density depletion in the lower ionosphere was 3 of 22 first studied with a simple model by Banks and Yasuhara (1978), and later also addressed in deBoer et al (2010) and Zettergren and Semeter (2012). Recently, Liang et al (2021) (hereafter referred to as LJ21) presented a comprehensive and dedicated study on the role of ion Pedersen transport in the dynamic variations of the lower ionosphere in a SAID channel. Using a two-dimensional (2D) time-dependent model tailored to SAID conditions, LJ21 found that the transport effect of ion Pedersen drifts leads to strong density depletion and conductance drop in the lower ionosphere over a large portion of SAID.…”

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confidence: 99%

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Model Simulation of SAID Intensification in the Ionosphere Under a Current Generator: The Role of Ion Pedersen Transport

2022

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During geomagnetically active intervals, latitudinally narrow channels of fast westward ion drifts were at times observed in the subauroral region. They are termed the “subauroral ion drifts” (SAID). The Strong Thermal Emission Velocity Enhancement (STEVE), a subauroral optical phenomenon, is intrinsically related to intense SAID. Recently, we had developed a two‐dimensional (2D) time‐dependent model to study the self‐consistent variations of the ionosphere under intense SAID. The present study further advances the model to a current generator scenario of SAID. By assuming magnetospheric field‐aligned current (FAC) inputs based on existing knowledge and observations, we model the self‐consistent variations of the ionosphere, with focus on the dynamic changes of the plasma density, the Pedersen conductance, and the electric field. We can reproduce the self‐consistent evolution of an intense SAID and its associated ionospheric dynamics such as extreme heating and depletion. We illustrate that the ion Pedersen drifts can cause dynamic density variations in the lower ionosphere. Positive feedback is found to exist between the self‐consistent variations of the electric field and the conductance: the ion Pedersen transport associated with the electric field leads to density depletion in the lower ionosphere, thus reducing the Pedersen conductance and further enhancing the electric field there. We conclude that such positive feedback is key to the formation of intense SAID's in the ionosphere.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Model Simulation of SAID Intensification in the Ionosphere Under a Current Generator: The Role of Ion Pedersen Transport

2022

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“…Related modeling indicating the coexistence of strong conductance gradients with the strong flows of sub auroral ionization drift, is shown recently in Liang et al. (2021). The resulting conductance structuring can be a source for field‐aligned currents; these ionospherically sourced field‐aligned currents can then be unstable to tearing modes and locally accelerate ambient thermal electrons, leading to the picket fence similarity to rayed auroral curtains.…”

Section: Introduction: Background and Premisementioning

confidence: 55%

“…The model includes self‐consistent electron energy descriptions, but does not include the kinetic turbulence effects discussed in Liang et al. (2021). However, our primary focus here is the Pedersen drift from multiple flow shears, which tends to dominate in these strong channels.…”

Section: Method: Gemini Model and Example Observational Driversmentioning

confidence: 99%

An Ionospheric Conductance Gradient Driver for Subauroral Picket Fence Visible Signatures Near STEVE Events

et al. 2022

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Reported observations of picket fence signatures associated with subauroral Strong Thermal Emission Velocity Enhancement (STEVE) emission events look strikingly similar to rayed auroral curtains. Rayed auroral curtains are often the visible signatures of tearing‐mode‐unstable current sheets with precipitating auroral electron current carriers. Picket fence signatures are not located where auroral precipitation explanations apply, and are closely collocated with STEVE emission events. A similar tearing‐mode‐instability explanation can be invoked with a different source for the originating field‐aligned current (FAC) sheet. In this explanation, the FAC sheet is sourced by ionospheric conductance gradients adjacent to the localized flows of the STEVE event. Geospace Environment Model of Ion‐Neutral Interactions (GEMINI) models of the 3D ionosphere near counterstreaming STEVE‐associated flow structures show the development of sufficiently strong current sheets for tearing mode instabilities to take hold. These instabilities can locally accelerate ambient ionospheric thermal electrons to the few eV needed for the reported observed green picket fence signatures.

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Model simulation of SAID intensification in the ionosphere under a current generator: the role of ion Pedersen transport

Liang

St.-Maurice

Donovan

2022

Preprint

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The sub-auroral ion drift (SAID) denotes a latitudinally narrow channel of fast westward ion drift in the sub-auroral region. The recently recognized sub-auroral optical phenomenon, the Strong Thermal Emission Velocity Enhancement (STEVE), is intrinsically related to intense SAIDs. Recently, we had developed a 2D time-dependent model to study the self-consistent variations of the ionosphere under intense SAID. The present study further advances the model to a current generator scenario of SAID. By assuming magnetospheric field-aligned current (FAC) inputs based on existing knowledge and observations, we model the self-consistent variations of the ionosphere, with focus on the dynamic changes of the plasma density, the Pedersen conductance, and the electric field. We can reproduce the self-consistent evolution of an intense SAID and its associated ionospheric dynamics such as extreme heating and depletion. We illustrate that the ion Pedersen drifts can cause dynamic density variations in the lower ionosphere. Positive feedback is found to exist between the self-consistent variations of the electric field and the conductance: the ion Pedersen transport associated with the electric field leads to density depletion in the lower ionosphere, thus reducing the Pedersen conductance and further enhancing the electric field there. We conclude that such positive feedback is key to the formation of intense SAID's in the ionosphere.

show abstract

A Time‐Dependent Two‐Dimensional Model Simulation of Lower Ionospheric Variations Under Intense SAID

Cited by 16 publications

References 96 publications

Model Simulation of SAID Intensification in the Ionosphere Under a Current Generator: The Role of Ion Pedersen Transport

Model Simulation of SAID Intensification in the Ionosphere Under a Current Generator: The Role of Ion Pedersen Transport

An Ionospheric Conductance Gradient Driver for Subauroral Picket Fence Visible Signatures Near STEVE Events

Model simulation of SAID intensification in the ionosphere under a current generator: the role of ion Pedersen transport

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