Electron acceleration in the ionospheric Alfven resonator

Chaston, C. C.; Bonnell, J. W.; Carlson, C. W.; Berthomier, M.; Peticolas, L. M.; Roth, I.; McFadden, J. P.; Ergun, R. E.; Strangeway, R. J.

doi:10.1029/2002ja009272

Cited by 110 publications

(137 citation statements)

References 38 publications

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“…It should be recognized that if this is the case, the visible aurora would not necessarily be on the same field lines as those containing the fast flow, as is sometimes assumed. This statement is also consistent with the observations from FAST that the poleward boundary region of the aurora is frequently characterized by broadband electron acceleration [Chaston et al, 2002b].…”

Section: Discussionsupporting

confidence: 80%

“…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: Introductionsupporting

confidence: 79%

“…[3] These events may represent a transitional phase in the aurora, since they are often observed at the poleward edge of the auroral zone [Chaston et al, 2002b] as well as in the auroral arc that first brightens at substorm onset [Mende et al, 2003] and during the decaying phase of the aurora [Semeter et al, 2001]. FAST observations show that such waves can drive bright, narrow auroral arcs [Chaston et al, 2003] and can account for 25-39% of the total electron energy deposited in the ionosphere by discrete arcs [Chaston et al, 2007].…”

Section: Introductionmentioning

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: Discussionsupporting

confidence: 80%

Section: Introductionsupporting

confidence: 79%

Section: Introductionmentioning

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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“…Specific spectral resonance structures measured on the ground have been considered evidence for IAR phenomena [Belyaev et al, 1990]. Subsequent in situ measurements have expanded our knowledge of IAR dynamics [Grzesiak, 2000;Chaston et al, 2002;Bösinger et al, 2004;Parent et al, 2010]. In addition to intrinsic spectral structures, the main characteristics of IAR shear Alfvén waves at high latitude include a wave vector in the parallel direction and oscillations of the electric and magnetic fields perpendicular to the geomagnetic field.…”

Section: Ionospheric Alfvén Resonatormentioning

confidence: 99%

Detection of ionospheric Alfvén resonator signatures in the equatorial ionosphere

et al. 2012

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.[1] The ionosphere response resulting from minimum solar activity during cycle 23/24 was unusual and offered unique opportunities for investigating space weather in the near-Earth environment. We report ultra low frequency electric field signatures related to the ionospheric Alfvén resonator detected by the Communications/Navigation Outage Forecasting System (C/NOFS) satellite in the equatorial region. These signatures are used to constrain ionospheric empirical models and offer a new approach for monitoring ionosphere dynamics and space weather phenomena, namely aeronomy processes, Alfvén wave propagation, and troposphere-ionosphere-magnetosphere coupling mechanisms.

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“…Transversely accelerated hydrogen and oxygen ions of tens to a few hundred eV suggest the existence of even shorter transverse scales of the wavefield. Fortunately, there is plenty of evidence of smaller-scale components in the electric as well as magnetic fields [e.g., Stasiewicz et al, 1997;Chaston et al, 2002]. They are probably not impressed from the generator but may rather be a secondary product of the interaction of the incoming wider wave with the ionospheric resonator by multiple reflections with periods in the 1 Hz range [Stasiewicz et al, 1997;Chaston et al, 2002;Lysak and Song, 2002].…”

Section: Alfvénic Arcs/onset Arcsmentioning

confidence: 99%

Six auroral generators: A review

Haerendel

2011

J. Geophys. Res.

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[1] The paper reviews generator processes and configurations of six types of auroral arcs: embedded arcs, Alfvénic arcs, onset arcs, poleward arcs during substorms, auroral streamers, and auroral spirals. The arcs and generators are elements in global current systems, which are classified as Types I and II after Boström. The arcs may be dominated by transient processes or be quasi-stationary. The main emphasis of the paper is on the generator forces. They are pressure gradient forces, magnetic normal or shear stresses, or inertial forces. For three cases, the arcs embedded in the oval convection, the poleward arc during substorms, and the auroral streamers, simple expressions are presented of the currents injected into the ionosphere by the generator process, allowing quantitative evaluations. The relations leading from these currents to other key auroral quantities are summarized. The apparent conflict between the widths of Alfvénic arcs and the transverse scales required for energy coupling to the topside ionospheric plasma is solved by assuming current and field filamentation by multiple reflections in the ionospheric Alfvén resonator. The substorm generator is described as a high-beta plasma layer arising from collapse of the tail current sheet. An essential element in this process is the shedding of excess flux tube entropy through energy dumping in the auroral acceleration process and ionospheric dissipation. The dynamics of this process needs further investigation. The physics of the connection between flow bursts in the tail plasma sheet and the flows associated with auroral streamers in the ionosphere is discussed. Regular auroral spirals and the westward traveling surge have in common a concentration of upward field-aligned current which demands strongly enhanced dissipation. They differ by the processes creating the upward current concentration.

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Electron acceleration in the ionospheric Alfven resonator

Cited by 110 publications

References 38 publications

Development of parallel electric fields at the plasma sheet boundary layer

Development of parallel electric fields at the plasma sheet boundary layer

Detection of ionospheric Alfvén resonator signatures in the equatorial ionosphere

Six auroral generators: A review

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