The Hot Electrons in and Above the Auroral Ionosphere: Observations and Physical Implications

Bryant, D. A.

doi:10.1007/978-1-4613-3652-5_16

Cited by 13 publications

(2 citation statements)

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“…Wave generation has been tentatively linked to the gradients in density, mean energy, and magnetic field strength across the boundary layer between the plasma sheet and the tail lobe [ Bryant , 1983]. This view was prompted by the finding that accelerated electron streams occur at boundaries between plasmas of different properties [ Bryant et al , 1972] and the frequent observation that auroral arcs occur between weaker, diffuse aurora on the equatorward side and even weaker aurora on the poleward side [ Bryant , 1994; Stenbaek‐Nielsen et al , 1998].…”

Section: Acceleration By Dynamic Electric Fieldsmentioning

confidence: 99%

The roles of static and dynamic electric fields in the auroral acceleration region

Bryant¹

2002

J. Geophys. Res.

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[1] Charged particles and electric fields measured by the Fast Auroral Snapshot satellite (FAST) are being widely interpreted as final vindication of the theory that the electrons responsible for the brightest and most highly structured forms of aurora gain their energy by being accelerated in static electric fields. However, measurements of electrostatic waves from the same satellite also give further impetus to the opposing theory that the electrons are energized by the dynamic electric fields of plasma waves. Consideration of the different capabilities of static and dynamic electric fields leads to a model of the auroral electron acceleration region incorporating acceleration by both types of fields. An experimental test of the model is suggested.

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Section: Acceleration By Dynamic Electric Fieldsmentioning

confidence: 99%

The roles of static and dynamic electric fields in the auroral acceleration region

Bryant¹

2002

J. Geophys. Res.

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“…Consideration of the energetics of the process leads to the suggestion that the acceleration may be essentially a plasma boundary phenomenon. for a wave interpretation of the phenomenon have developed over a number of years in parallel with an emerging wave theory [Bryant, 1981[Bryant, , 1983[Bryant, , 1990; Bingham et al, 1984, 1988; Bryant et al, 1991a, hi. The possibility of the process being universal throughout space platohas has also been discussed [Bryant, 1987, 1990].…”

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confidence: 99%

Velocity‐space distributions of wave‐accelerated auroral electrons

Bryant¹,

Perry²

1995

J. Geophys. Res.

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The possibility that auroral electrons might be accelerated by electrostatic wave turbulence is further explored. Electron velocity distributions resulting from lower hybrid wave turbulence are modeled as functions of velocities parallel and perpendicular to the magnetic vector. The model, which is highly stylized with focus on the underlying physics, is found to account readily for the wide range of experimentally observed features such as "beams," "conics," and "widened loss cones." Consideration of the energetics of the process leads to the suggestion that the acceleration may be essentially a plasma boundary phenomenon. for a wave interpretation of the phenomenon have developed over a number of years in parallel with an emerging wave theory [Bryant, 1981[Bryant, , 1983[Bryant, , 1990; Bingham et al., 1984, 1988; Bryant et al., 1991a, hi. The possibility of the process being universal throughout space platohas has also been discussed [Bryant, 1987, 1990]. A commonality with acceleration in laboratory plasmas has clearly emerged, as has the dynamic equivalence of acceleration by Landau damping of electrostatic wave packets and Fermi's [1949] mechanism of cosmic ray acceleration by momentum exchange with moving magnetic barriers [Bryant, 1992, 1993]. An earlier modelling of the acceleration of auroral electrons by lower hybrid turbulence [Bryant et al., 1991b] showed that the velocity distribution parallel to the magnetic vector, f(Vl[ , V_L --0), could be reproduced satisfactorily using a stylized Monte Carlo model of the stochastic process. The characteristic spectral peak, the high-energy tail, and the invariance at low energies were all found to arise naturally from momentum exchange between electrons and lower hybrid wave packets. By adding the effects of the magnetic mirror force and a nominal atmosphere we now extend the model to two velocity dimensions, parallel and perpendicular to the magnetic vector B, in order to show that the model also satisfactorily produces the many wellestablished features of the two-dimensional (2-d) distri-Now at Goring-on-Thames, England, United Kingdom Paper nmnber 95JA00991. 0148-0227/95/95J A-00991 $05.00 button f(vll , V_L). Beams, conics, an extended loss cone, and other features are found to anticipate quite closely the experimental observations. We begin by recalling the properties of lower hybrid waves. We then outline our stylized model of the interaction with electrons, pointing out the two basic types of interaction that can be expected to occur: one being an "electrostatic Fermi acceleration," the other being a general heating. A series of examples then reveals the properties of such an accelerator and the sensitivity of the resultant electron distribution to wave properties and other controlling factors. The effects of different combinations of the governing parameters are then summarized. We then suggest how the various experimentally observed features might be interpreted in terms of the wave theory. The required electric field strengths are estimated and the e...

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Magnetosphere-ionosphere interactions —near-Earth manifestations of the plasma Universe

Fälthammar

1988

Astrophys Space Sci

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The Hot Electrons in and Above the Auroral Ionosphere: Observations and Physical Implications

Cited by 13 publications

References 50 publications

The roles of static and dynamic electric fields in the auroral acceleration region

The roles of static and dynamic electric fields in the auroral acceleration region

Velocity‐space distributions of wave‐accelerated auroral electrons

Magnetosphere-ionosphere interactions —near-Earth manifestations of the plasma Universe

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