Evidence for generation of unstable suprathermal electron population in the auroral <i>F</i> region

Akbari, H.; Semeter, J. L.; Hirsch, Michael; Guio, P.; Nicolls, M. J.

doi:10.1002/2014gl062598

Cited by 5 publications

(7 citation statements)

References 31 publications

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“…ISR detections are much different from in situ measurements in that they indicate enhanced wave activities at a specific spatial scale, determined by the ISR probing wave number. This, in turn, puts additional requirements on the characteristic energy of the electron beams and/or the dynamics of turbulence (for more context see Akbari et al []).…”

Section: Introductionmentioning

confidence: 99%

Zakharov simulations of beam‐induced turbulence in the auroral ionosphere

et al. 2016

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Recent detections of strong incoherent scatter radar echoes from the auroral F region, which have been explained as the signature of naturally produced Langmuir turbulence, have motivated us to revisit the topic of beam‐generated Langmuir turbulence via simulation. Results from one‐dimensional Zakharov simulations are used to study the interaction of ionospheric electron beams with the background plasma at the F region peak. A broad range of beam parameters extending by more than 2 orders of magnitude in average energy and electron number density is considered. A range of wave interaction processes, from a single parametric decay, to a cascade of parametric decays, to formation of stationary density cavities in the condensate region, and to direct collapse at the initial stages of turbulence, is observed as we increase the input energy to the system. The effect of suprathermal electrons, produced by collisional interactions of auroral electrons with the neutral atmosphere, on the dynamics of Langmuir turbulence is also investigated. It is seen that the enhanced Landau damping introduced by the suprathermal electrons significantly weakens the turbulence and truncates the cascade of parametric decays.

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Section: Introductionmentioning

confidence: 99%

Zakharov simulations of beam‐induced turbulence in the auroral ionosphere

et al. 2016

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“…On the other hand, conjugate measurements by radars and high-resolution optical imagers have shown that LT echoes are associated with dynamic smallscale auroral structures likely related to dispersive-scale Alfvén waves (see Figures 9A,B). Results from one-dimensional Zakharov simulations suggest that the measured ISR spectra are best reproduced numerically when the modeled electron beams extend a positive slope to energies as low as 5 eV, such that ion-acoustic waves are induced by parametric decays at wavenumbers greater than k detection (Akbari et al, 2015). Such low energy components of an electron beam, however, would likely be significantly modified by collisions at altitudes of some radar observations between 180 and 300 km.…”

Section: Discussion Of Several Open Questionsmentioning

confidence: 97%

“…Such low energy components of an electron beam, however, would likely be significantly modified by collisions at altitudes of some radar observations between 180 and 300 km. This leads to a speculation that perhaps an unstable feature of the electron distribution function which eventually gives rise to LT echoes is produced locally at ionospheric heights in response to electron precipitation (Akbari et al, 2015). Such a speculation, however, is not backed with concrete evidence.…”

Section: Discussion Of Several Open Questionsmentioning

confidence: 98%

Langmuir Turbulence in the Auroral Ionosphere: Origins and Effects

Akbari

LaBelle

Newman

2021

Front. Astron. Space Sci.

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Theory and observations of Langmuir waves and turbulence induced in the auroral ionosphere by electron beams of magnetospheric-origin are reviewed. The theoretical discussions include a brief description of the electrostatic dispersion relation, excitation of Langmuir waves by electron beams, and the stability of beam distributions. The theory of Langmuir turbulence—including the parametric decay instability and wave collapse—is also briefly discussed. The main focus of the review, however, is on the observations of Langmuir waves and turbulence in the ionosphere by in-situ and ground-based sensors. A summary of five decades of in-situ wave and particle observations is presented and combined with a collection of more recent results from ground-based instruments. The ground-based observations include signatures of Langmuir turbulence in the form of coherent echoes in incoherent scatter radar measurements; signatures of electron beams in the form of auroral morphologies recorded by high-speed, high-resolution optical imagers; and electromagnetic emissions received on the ground at high latitudes. Uniting the various observations obtained by the vastly different sensors is shown to provide further insight into the micro-scale processes that occur in the ionosphere. Also discussed in this review is the potential of the ground-based sensors to provide a broader spatial and temporal context for single-point in-situ measurements of such processes.

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“…The SimISR tool is useful for identifying situations where assumptions in the parameter fitting break down. For example, a number of studies have explored the case where ISR parameter measurements and spectra show evidence of non‐Maxwellian plasma behavior [see, e.g., Akbari et al , , , for AMISR examples]. Future studies using the simulator could help create a training set that can be used with a pattern recognition algorithm to identify cases where normal fitting procedures may be incorrect due to violation of Maxwellian assumptions.…”

Section: Simulation Examplesmentioning

confidence: 99%

Observability of ionospheric space‐time structure with ISR: A simulation study

et al. 2017

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The sources of error from electronically steerable array (ESA) incoherent scatter radar (ISR) systems are investigated both theoretically and with use of an open‐source ISR simulator, developed by the authors, called Simulator for ISR (SimISR). The main sources of error incorporated in the simulator include statistical uncertainty, which arises due to nature of the measurement mechanism and the inherent space‐time ambiguity from the sensor. SimISR can take a field of plasma parameters, parameterized by time and space, and create simulated ISR data at the scattered electric field (i.e., complex receiver voltage) level, subsequently processing these data to show possible reconstructions of the original parameter field. To demonstrate general utility, we show a number of simulation examples, with two cases using data from a self‐consistent multifluid transport model. Results highlight the significant influence of the forward model of the ISR process and the resulting statistical uncertainty on plasma parameter measurements and the core experiment design trade‐offs that must be made when planning observations. These conclusions further underscore the utility of this class of measurement simulator as a design tool for more optimal experiment design efforts using flexible ESA class ISR systems.

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Evidence for generation of unstable suprathermal electron population in the auroral F region

Cited by 5 publications

References 31 publications

Zakharov simulations of beam‐induced turbulence in the auroral ionosphere

Zakharov simulations of beam‐induced turbulence in the auroral ionosphere

Langmuir Turbulence in the Auroral Ionosphere: Origins and Effects

Observability of ionospheric space‐time structure with ISR: A simulation study

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