Driven Alfven waves and electron acceleration: A FAST case study

Chaston, C. C.

doi:10.1029/2001gl013842

Cited by 127 publications

(159 citation statements)

References 18 publications

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“…However, the FAST spacecraft [e.g., Chaston et al, 2000Chaston et al, , 2002aChaston et al, , 2003Chaston et al, , 2006Chaston et al, , 2007 has observed these broadband distributions in conjunction with Alfvénic fluctuations, suggesting that these electrons are accelerated by parallel electric fields in kinetic Alfvén waves. This conclusion was supported by models for the Alfvén wave acceleration of these electrons [e.g., Kletzing, 1994;Thompson and Lysak, 1996;Chaston et al, 1999Chaston et al, , 2000Chaston et al, , 2002aChaston et al, , 2002bKletzing and Hu, 2001;Lysak and Song, 2003a, 2003b, which gave results consistent with observation. Thus, such events have been termed the "Alfvénic aurora.…”

Section: Introductionmentioning

confidence: 99%

Development of parallel electric fields at the plasma sheet boundary layer

Lysak

Song

2011

J. Geophys. Res.

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[1] Many measurements of auroral particles, in particular recent measurements from the FAST satellite, indicate that the auroral electron distribution is often broad in energy and field-aligned in pitch angle. Such electrons are seen in conjunction with strong kinetic Alfvén waves with small perpendicular wavelength, and so the aurora produced by these electrons has been termed the "Alfvénic aurora." The Alfvénic aurora is predominant at the polar cap boundary of the aurora as well as in the auroral arc that brightens during substorm onset. The process of forming parallel electric fields in Alfvén waves has been investigated by means of three-dimensional two-fluid simulations. Waves with small perpendicular wavelengths can be produced by phase mixing when perpendicular gradients are present in the plasma. At lower altitudes, Alfvén waves can interact with the ionospheric Alfvén resonator and phase mix to scales of a few kilometers. At higher altitudes, the electron thermal speed becomes comparable or larger than the Alfvén speed, and parallel electric fields due to the Landau resonance can develop. This has been modeled in the fluid code by an approximation to the plasma dispersion function used in kinetic theory. Phase mixing is most effective when there are strong gradients, such as at the plasma sheet boundary layer. Simulations indicate that these processes can produce parallel electric fields on scales of a few kilometers (in the cold plasma case) to a few tens of kilometers (in the warm plasma case), comparable to the scale sizes of auroral arcs.

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Section: Introductionmentioning

confidence: 99%

Development of parallel electric fields at the plasma sheet boundary layer

Lysak

Song

2011

J. Geophys. Res.

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“…Lysak (1993) included electron inertia and a more realistic V A profile based on a dipole magnetic field to show that effects from the resonator persisted when parallel electric fields were present. This model was used to investigate electron acceleration through test particle models (Thompson and Lysak, 1996;Chaston et al, 2000Chaston et al, , 2002a, indicating that field aligned beams of electrons observed from the FAST satellite were consistent with acceleration due to parallel electric fields in the resonator.…”

Section: Discussionmentioning

confidence: 99%

On the coupling of fast and shear Alfvén wave modes by the ionospheric Hall conductance

2013

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There are two low frequency, magnetised, cold plasma wave modes that propagate through the Earth's magnetosphere. These are the compressional (fast) and the shear Alfvén modes. The fast mode distributes energy throughout the magnetosphere with the ability to propagate across the magnetic field. Previous studies of coupling between these two modes have often focussed on conditions necessary for mode coupling to occur in the magnetosphere. However, Kato and Tamao (1956) predicted mode coupling would occur for non-zero Hall currents. Recently, the importance of the Hall conductance in the ionosphere for low frequency wave propagation has been studied using one dimensional (1-D) models. In this paper we describe effects of the ionosphere Hall conductance on field line resonance and higher frequency, 0.1-5 Hz waves associated with the Ionospheric Alfvén Resonator (IAR). The Hall conductance reduces the damping time of field line resonances and Joule dissipation into the ionosphere. The Hall conductance also couples shear Alfvén waves trapped in the IAR to fast mode waves that propagate across the ambient magnetic field in an ionospheric waveguide. This coupling leads to the production of low frequency magnetic fields on the ground that can be observed by magnetometers.

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“…Broadband acceleration in upward, downward, or no FAC regions can be attributed to small-scale dispersive Alfvén waves that create time-varying field-aligned electric field that disperses electron energy [e.g., Chaston et al, 2002;Watt and Rankin, 2009;Wing et al, 2013]. On the other hand, monoenergetic electrons are usually attributed to quasi-static potential drops, which are typically associated with upward FAC regions and global magnetic field configuration or low-frequency waves [Damiano and Johnson, 2012].…”

Section: 1002/2015gl064229mentioning

confidence: 99%

On the field‐aligned electric field in the polar cap

Wing

Fairfield

Ohtani

2015

Geophysical Research Letters

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The Johns Hopkins University Applied Physics Laboratory open‐field line particle precipitation model predicts downward field‐aligned electric field to maintain charge quasi‐neutrality. Previous studies confirmed the existence of such electric fields. However, the present study shows that upward field‐aligned electric field can be found within upward field‐aligned current (FAC) region. In the upward FAC region, upward electric field that accelerates electron downward is seen with the occurrence rates of 82%–96%. In contrast, the occurrence rates in the downward FAC regions are 3%–11%. Polar rain electrons located in the upward FAC region adjacent to closed field lines often show a ramping up of energy with increasing latitude before reaching a plateau. This plateau may be attributed to the magnetosheath electrons that progressively have higher antisunward velocity and lower density with increasing distance from the subsolar point before they asymptotically reach the solar wind values.

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Driven Alfven waves and electron acceleration: A FAST case study

Cited by 127 publications

References 18 publications

Development of parallel electric fields at the plasma sheet boundary layer

Development of parallel electric fields at the plasma sheet boundary layer

On the coupling of fast and shear Alfvén wave modes by the ionospheric Hall conductance

On the field‐aligned electric field in the polar cap

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