Polar spacecraft based comparisons of intense electric fields and Poynting flux near and within the plasma sheet‐tail lobe boundary to UVI images: An energy source for the aurora

Wygant, J. R.; Keiling, A.; Cattell, C. A.; Johnson, Michael; Lysak, R. L.; Temerin, M.; Mozer, F. S.; Kletzing, C.; Scudder, J. D.; Peterson, W. K.; Russell, C. T.; Parks, G. K.; Brittnacher, M.; Spann, James F.

doi:10.1029/1999ja900500

Cited by 269 publications

(321 citation statements)

References 33 publications

(15 reference statements)

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“…The electric field structures shown here have a spatial scale across the magnetic field of 20-50 km mapped to the ionosphere, or about 200-500 km at 5 R E . This compares favorably with the spatial scales of 80-400 km estimated by Wygant et al [2000]. The ion acoustic gyroradius at this altitude is about 10 km for the 1000 eV temperature assumed in the simulation.…”

Section: Results: Mode Conversion At the Plasma Sheet Boundary Layersupporting

confidence: 74%

“…[29] Figure 8 shows the line profiles as a function of x (the latitudinal direction) at the same y values as the contour plots and at a radial distance of 5 R E for comparison with the Polar observations of Wygant et al [2000]. Unlike in the contour plots, the field magnitudes in Figures 8a and 8b have not been mapped to ionospheric heights to allow for direct comparison with observations.…”

Section: Results: Mode Conversion At the Plasma Sheet Boundary Layermentioning

confidence: 99%

“…[4] In addition to these observations at low altitude, Polar observations have indicated that strong Alfvénic Poynting flux is often observed at the plasma sheet boundary layer [e.g., Wygant et al, 2000Wygant et al, , 2002Keiling et al, 2000Keiling et al, , 2001Keiling et al, , 2002. This Poynting flux, mapped to the ionosphere, was sufficient to provide enough energy for auroral arcs.…”

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: Results: Mode Conversion At the Plasma Sheet Boundary Layersupporting

confidence: 74%

Section: Results: Mode Conversion At the Plasma Sheet Boundary Layermentioning

confidence: 99%

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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“…Measurements from the FAST spacecraft include many observations of sheet currents where the current density as measured by the magnetometer is quantitatively consistent with the current carriers measured by the electron detectors [Peria et al, 2000, Carlson et al, 1998]. Observations of Alfvénic activity from Polar [Wygant et al, 2000;Keiling et al, 2001], Freja [Louarn et al, 1994], and rocket data [Knudsen et al, 1990[Knudsen et al, , 1992 include many examples of electric and magnetic field fluctuations which clearly satisfy conditions for Alfvén wave activity.…”

Section: Interpreting Magnetic Fluctuationsmentioning

confidence: 99%

Multipoint measurements of field‐aligned current density in the auroral zone

et al. 2003

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[1] In this paper we present the analysis and interpretation of a multipoint observation of magnetic field structures at the poleward edge of a premidnight auroral arc by the Enstrophy sounding rocket mission. Four Free-Flying Magnetometers (FFMs) employing autonomous nanospacecraft technology were deployed from the main payload during the flight, and multipoint magnetic field measurements were made. Signatures consistent with both spatial and temporal interpretations were found to be present when large fluctuations in B were seen at the edge of an arc as the rocket flew into the polar cap. Reasons for the interpretation of spatial or temporal features are given and supported by a simple model of multiple payloads crossing through several moving current sheets and a study of the fine structure of this auroral event using multipoint, correlative wavelet analysis to find velocities of structures at different scale sizes. We show that the direct measurement method of current density using multipoint measurement of magnetic fields gives us a different current density than what would be inferred from a single-point measurement and that the multipoint measurement also provides an inherent check on the validity of the measurement through a calculation of the divergence of the measured B.INDEX TERMS:

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“…These high-speed flows can be manifested as bursty bulk flows (BBFs) and other sporadic and intermittent phenomena [e.g., Scholer et al, 1984;Angelopoulos et al, 1992;Chen and Wolf, 1993;Angelopoulos et al, 2002]. For example, the large substorm current wedge is believed to be caused by the braking and diversion of earthward directed flows closer to the inner boundary of the plasma sheet, resulting in the generation of electromagnetic power, which eventually can power the aurora [Wygant et al, 2000] as well as cause ionospheric Joule heating.…”

Section: Introductionmentioning

confidence: 99%

Energy conversion regions as observed by Cluster in the plasma sheet

et al. 2011

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[1] In this article we present a review of recent studies of observations of localized energy conversion regions (ECRs) observed by Cluster in the plasma sheet at altitudes of 15-20R E . By examining variations in the power density, E · J, where E is the electric field and J is the current density, we show that the plasma sheet exhibits a high level of fine structure. Approximately three times as many concentrated load regions (CLRs) (E · J > 0) as concentrated generator regions (CGRs) (E · J < 0) are identified, confirming the average load character of the plasma sheet. Some ECRs are found to relate to auroral activity. While ECRs are relevant for the energy conversion between the electromagnetic field and the particles, bursty bulk flows (BBFs) play a central role for the energy transfer in the plasma sheet. We show that ECRs and BBFs are likely to be related, although details of this relationship are yet to be explored. The plasma sheet energy conversion increases rather simultaneously with increasing geomagnetic activity in both CLRs and CGRs. Consistent with large-scale magnetotail simulations, most of the observed ECRs appear to be rather stationary in space but varying in time. We estimate that the ECR lifetime and scale size are a few minutes and a few R E , respectively. It is conceivable that ECRs rise and vanish locally in significant regions of the plasma sheet, possibly oscillating between load and generator character, while some energy is transmitted as Poynting flux to the ionosphere.

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Polar spacecraft based comparisons of intense electric fields and Poynting flux near and within the plasma sheet‐tail lobe boundary to UVI images: An energy source for the aurora

Cited by 269 publications

References 33 publications

Development of parallel electric fields at the plasma sheet boundary layer

Development of parallel electric fields at the plasma sheet boundary layer

Multipoint measurements of field‐aligned current density in the auroral zone

Energy conversion regions as observed by Cluster in the plasma sheet

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