On the kinetic dispersion relation for shear Alfvén waves

Lysak, R. L.; Lotko, W.

doi:10.1029/95ja03712

Cited by 400 publications

(461 citation statements)

References 23 publications

(16 reference statements)

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“…[13] The dispersion relation for kinetic Alfvén waves has been derived by a number of authors [e.g., Lysak and Lotko, 1996;Gekelman et al, 1997;Lysak, 2008]. However, the dispersion relation is written in terms of frequency and wave number, and so is not appropriate for a time domain simulation that can treat the inhomogeneities of the system.…”

Section: Phase Mixing In the Ionospheric Alfvén Resonatormentioning

confidence: 99%

“…[22] Lysak and Lotko [1996] have shown that this twofluid description gives a good approximation to the real part of the full kinetic dispersion relation. However, the twofluid description does not include Landau damping, which can be significant for the warm plasma case and for short perpendicular wavelength.…”

Section: Kinetic Alfvén Waves In the Warm Plasma Regionmentioning

confidence: 99%

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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: Phase Mixing In the Ionospheric Alfvén Resonatormentioning

confidence: 99%

Section: Kinetic Alfvén Waves In the Warm Plasma Regionmentioning

confidence: 99%

Development of parallel electric fields at the plasma sheet boundary layer

Lysak

Song

2011

J. Geophys. Res.

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“…A dispersive Alfvén wave (DAW) (e.g. Lysak and Lotko, 1996;Stasiewicz et al, 2000, and references therein) may, therefore, enhance both its inertial and kinetic characteristics, and develop a field-aligned electric field in the wave front when it propagates at a small angle to the Earth's magnetic field. These Alfvén waves are, therefore, often suggested as candidates for auroral zone fieldaligned electron acceleration processes.…”

Section: Introductionmentioning

confidence: 99%

Electromagnetic waves and bursty electron acceleration: implications from Freja

et al. 2002

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Abstract. Dispersive Alfvén wave activity is identified in four dayside auroral oval events measured by the Freja satellite. The events are characterized by ion injection, bursty electron precipitation below about 1 keV, transverse ion heating and broadband extremely low frequency (ELF) emissions below the lower hybrid cutoff frequency (a few kHz). Largescale density depletions/cavities, as determined by the Langmuir probe measurements, and strong electrostatic emissions are often observed simultaneously. A correlation study has been carried out between the E and B field fluctuations below 64 Hz and 10 Hz, respectively, (the DC instruments upper threshold) and the characteristics of the precipitating electrons. This study revealed that the energisation of electrons is indeed related to the broadband ELF emissions and that the electrostatic component plays a predominant role during very active magnetospheric conditions. Furthermore, the effect of the ELF electromagnetic emissions on the larger scale field-aligned current systems has been investigated, and it is found that such an effect cannot be detected. Instead, the Alfvénic activity creates a local region of field-aligned currents. It is suggested that dispersive Alfvén waves set up these local field-aligned current regions and, in turn, trigger more electrostatic emissions during certain conditions. In these regions, ions are transversely heated, and large-scale density depletions/cavities may be created during especially active periods.

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“…[4] Therefore, most of the theories of auroral acceleration by waves are based on inertial Alfvén waves (see for instance Kletzing [1994], Lysak and Lotko [1996], and Watt and Rankin [2008]). Bridging with the early models cited at the beginning of the introduction, we can see now that the time varying electric fields associated to the non stationary acceleration structures [Hultqvist et al, 1988] are, in many cases, identified as inertial Alfvén wave electric fields.…”

Section: Introductionmentioning

confidence: 99%

Electron acceleration by an Alfvénic pulse propagating in an auroral plasma cavity

Mottez

Génot

2011

J. Geophys. Res.

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[1] With the help of a 2.5-D particle-in-cell simulation code, we investigate the physics of the acceleration of auroral electrons, through the interaction of an isolated Alfvén wave packet with a plasma density cavity. The cavity is edged by density gradients perpendicular to the magnetic field. We show that a single passing of an isolated wave packet over a (infinite) cavity creates an electron beam. It triggers local current and beam-plasma instabilities and small-scale coherent electric structures. The energy flux of downgoing electrons is significantly increased, whereas upgoing electrons are also accelerated, even if no beam is formed. Accelerated electrons remain after the passage of the Alfvénic pulse, allowing the observation of energetic particles without any significant electromagnetic perturbation. The dependence of this process on the electron to ion mass ratio is consistent with its control by inertial effects.Citation: Mottez, F., and V. Génot (2011), Electron acceleration by an Alfvénic pulse propagating in an auroral plasma cavity, J. Geophys. Res., 116,

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On the kinetic dispersion relation for shear Alfvén waves

Cited by 400 publications

References 23 publications

Development of parallel electric fields at the plasma sheet boundary layer

Development of parallel electric fields at the plasma sheet boundary layer

Electromagnetic waves and bursty electron acceleration: implications from Freja

Electron acceleration by an Alfvénic pulse propagating in an auroral plasma cavity

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