Direct measurement of electron sloshing of an inertial Alfvén wave

Schroeder, James W.; Skiff, F.; Kletzing, C.; Howes, G. G.; Carter, T. A.; Dorfman, S.

doi:10.1002/2016gl068865

Cited by 10 publications

(7 citation statements)

References 21 publications

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“…2b, we plot measurements of the total perturbation δg e (v z ) = g e (v z ) − g e0 (v z ) over 2π of Alfvén wave phase, showing a signal along the vertical axis dominated by the fundamental mode of oscillations g e1 (v z ) at the frequency ω of the Alfvén wave. A previously derived analytical solution to the linearized Boltzmann equation 44,45 , shown in Fig. 2c, reproduces the dominant features of this pattern using only g e1 (v z ).…”

Section: Resultssupporting

confidence: 54%

Laboratory measurements of the physics of auroral electron acceleration by Alfvén waves

et al. 2021

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While the aurora has attracted attention for millennia, important questions remain unanswered. Foremost is how auroral electrons are accelerated before colliding with the ionosphere and producing auroral light. Powerful Alfvén waves are often found traveling Earthward above auroras with sufficient energy to generate auroras, but there has been no direct measurement of the processes by which Alfvén waves transfer their energy to auroral electrons. Here, we show laboratory measurements of the resonant transfer of energy from Alfvén waves to electrons under conditions relevant to the auroral zone. Experiments are performed by launching Alfvén waves and simultaneously recording the electron velocity distribution. Numerical simulations and analytical theory support that the measured energy transfer process produces accelerated electrons capable of reaching auroral energies. The experiments, theory, and simulations demonstrate a clear causal relationship between Alfvén waves and accelerated electrons that directly cause auroras.

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Section: Resultssupporting

confidence: 54%

Laboratory measurements of the physics of auroral electron acceleration by Alfvén waves

et al. 2021

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“…It can be widely used to estimate the local rate of transfer of energy density in phase space in kinetic numerical simulations not only of kinetic plasma turbulence , but also of collisionless magnetic reconnection and particle acceleration. And it can also be used to investigate the weakly collisional dynamics in spacecraft measurements and laboratory experiments (Schroeder et al 2016). A major motivation for the work presented here is to develop a mature field-particle correlation method that can be used as the primary tool for the analysis of measurements from current, upcoming and proposed spacecraft missions that are focused on the kinetic microphysics of weakly collisional heliospheric plasmas, including the Magnetospheric Multiscale (MMS), Solar Probe Plus, Solar Orbiter and Turbulent Heating ObserveR (THOR) missions.…”

Section: Resultsmentioning

confidence: 99%

Diagnosing collisionless energy transfer using field–particle correlations: Vlasov–Poisson plasmas

2017

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Turbulence plays a key role in the conversion of the energy of large-scale fields and flows to plasma heat, impacting the macroscopic evolution of the heliosphere and other astrophysical plasma systems. Although we have long been able to make direct spacecraft measurements of all aspects of the electromagnetic field and plasma fluctuations in near-Earth space, our understanding of the physical mechanisms responsible for the damping of the turbulent fluctuations in heliospheric plasmas remains incomplete. Here we propose an innovative field–particle correlation technique that can be used to measure directly the secular energy transfer from fields to particles associated with collisionless damping of the turbulent fluctuations. Furthermore, this novel procedure yields information about the collisionless energy transfer as a function of particle velocity, providing vital new information that can help to identify the dominant collisionless mechanism governing the damping of the turbulent fluctuations. Kinetic plasma theory is used to devise the appropriate correlation to diagnose Landau damping, and the field–particle correlation technique is thoroughly illustrated using the simplified case of the Landau damping of Langmuir waves in a 1D-1V (one dimension in physical space and one dimension in velocity space) Vlasov–Poisson plasma. Generalizations necessary to apply the field–particle correlation technique to diagnose the collisionless damping of turbulent fluctuations in the solar wind are discussed, highlighting several caveats. This novel field–particle correlation technique is intended to be used as a primary analysis tool for measurements from current, upcoming and proposed spacecraft missions that are focused on the kinetic microphysics of weakly collisional heliospheric plasmas, including the Magnetospheric Multiscale (MMS), Solar Probe Plus, Solar Orbiter and Turbulence Heating ObserveR (THOR) missions.

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“…Further analysis considers the importance of non-Alfv enic terms included in the model. While preliminary results were given in a letter by Schroeder et al, 13 this longer paper includes a more thorough discussion of the experiment, theory, and analysis, and also includes several more detailed results.…”

Section: Introductionmentioning

confidence: 99%

Linear theory and measurements of electron oscillations in an inertial Alfvén wave

et al. 2017

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The physics of the aurora is one of the foremost unsolved problems of space physics. The mechanisms responsible for accelerating electrons that precipitate onto the ionosphere are not fully understood. For more than three decades, particle interactions with inertial Alfv en waves have been proposed as a possible means for accelerating electrons and generating auroras. Inertial Alfv en waves have an electric field aligned with the background magnetic field that is expected to cause electron oscillations as well as electron acceleration. Due to the limitations of spacecraft conjunction studies and other multi-spacecraft approaches, it is unlikely that it will ever be possible, through spacecraft observations alone, to confirm definitively these fundamental properties of the inertial Alfv en wave by making simultaneous measurements of both the perturbed electron distribution function and the Alfv en wave responsible for the perturbations. In this laboratory experiment, the suprathermal tails of the reduced electron distribution function parallel to the mean magnetic field are measured with high precision as inertial Alfv en waves simultaneously propagate through the plasma. The results of this experiment identify, for the first time, the oscillations of suprathermal electrons associated with an inertial Alfv en wave. Despite complications due to boundary conditions and the finite size of the experiment, a linear model is produced that replicates the measured response of the electron distribution function. These results verify one of the fundamental properties of the inertial Alfv en wave, and they are also a prerequisite for future attempts to measure the acceleration of electrons by inertial Alfv en waves. Published by AIP Publishing.

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Direct measurement of electron sloshing of an inertial Alfvén wave

Cited by 10 publications

References 21 publications

Laboratory measurements of the physics of auroral electron acceleration by Alfvén waves

Laboratory measurements of the physics of auroral electron acceleration by Alfvén waves

Diagnosing collisionless energy transfer using field–particle correlations: Vlasov–Poisson plasmas

Linear theory and measurements of electron oscillations in an inertial Alfvén wave

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