Electron temperatures during rapid subauroral ion drift events

Moffett, R. J.; Ennis, A. E.; Bailey, G. J.; Heelis, R. A.; Brace, L. H.

doi:10.1007/s005850050615

Cited by 17 publications

(38 citation statements)

References 10 publications

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“…This significant distinction is discussed by Moffett et al (1998), and in this study is most evident for Case g in Figure 1. This significant distinction is discussed by Moffett et al (1998), and in this study is most evident for Case g in Figure 1.…”

Section: Discussionmentioning

confidence: 53%

Steve: The Optical Signature of Intense Subauroral Ion Drifts

Archer

Gallardo‐Lacourt

Perry

et al. 2019

Geophysical Research Letters

102

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Little is currently known about the optical phenomenon known as Steve. The first scientific publication on the subject suggests that Steve is associated with an intense subauroral ion drift (SAID). However, additional inquiry is warranted as this suggested relationship as it is based on a single case study. Here we present eight occurrences of Steve with coincident or near‐coincident measurements from the European Space Agency's Swarm satellites and show that Steve is consistently associated with SAID. When satellite observations coincident with Steve are compared to that of typical SAID, we find the SAID associated with Steve to have above average peak ion velocities and electron temperatures, as well as extremely low plasma densities.

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Section: Discussionmentioning

confidence: 53%

Steve: The Optical Signature of Intense Subauroral Ion Drifts

Archer

Gallardo‐Lacourt

Perry

et al. 2019

Geophysical Research Letters

102

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“…SAID/SAPS‐related density troughs are formed due to enhanced rates,

k_{1, 2}

, of charge exchange of

O^{+}

ions with

N_{2}

(

k_{1}

) and

O_{2}

(

k_{2}

) and subsequent fast recombination of

N O^{+}

and

O_{2}^{+}

ions (e.g., Schunk et al, ; Pavlov, ; Moffett et al, ) and ion outflows (Anderson et al, ). The depletion time is about

τ \sim {((), k_{1} \cdot false[N_{2} false] + k_{2} \cdot false[O_{2} false])}^{- 1} \sim 10

–15 min.…”

Section: Discussionmentioning

confidence: 99%

STEVE and the Picket Fence: Evidence of Feedback‐Unstable Magnetosphere‐Ionosphere Interaction

Mishin

Streltsov

2019

Geophysical Research Letters

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This paper aims to extend the understanding of Strong Thermal Emission Velocity Enhancement (STEVE) and the Picket Fence related to strong subauroral ion drifts (SAID). We numerically demonstrated that precipitating energetic electrons are critical for the structuring of the Picket Fence. It is created by feedback-unstable magnetosphere-ionosphere interactions driven by the SAID electric field when the Hall conductance created by energetic (≥1 keV) electrons exceeds the Pedersen conductance. We show that thermal excitation of the red-line emission in STEVE is inhibited by inelastic collisions with molecular nitrogen. Suprathermal (≤500 eV) electrons coming from the turbulent plasmasphere appear to be the major source. We also show that the chemiluminescencent and radiative attachment reactions do not explain the short-wavelength part of the STEVE continuum and argue that accounting for vibrational excitation may resolve the problem. Atmosphere's upwelling due to enhanced ion-neutral drag leads to the increased abundance of molecular components relative to atomic oxygen.

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“…On the other hand, there are numerous examples when enhanced electron temperatures and density troughs are observed in regions of high ion drift speeds and high ion temperatures, especially during more strongly disturbed conditions (e.g. Foster et al, 1994;Moffett et al, 1998;Förster et al, 1999;Wang et al, 2006 1 ; and references therein). Therefore any generalization should be considered with due caution.…”

Section: Mean Latitudinal Profilesmentioning

confidence: 99%

Subauroral electron temperature enhancement in the nighttime ionosphere

Prölss

2006

Ann. Geophys.

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Abstract. In the nightside subauroral region, heat transfer from the ring current causes a significant increase in the electron temperature of the upper ionosphere. Using DE-2 satellite data, we investigate the properties of this remarkable feature. We find that the location of the temperature enhancement is primarily dependent on the level of geomagnetic activity. For geomagnetically quiet conditions ()the temperature peak is located slightly poleward of 60° invariant latitude. For each decrease in the Dst index by 10 nT, it moves equatorward by about one degree. To a lesser degree, the location of the heating effect also depends on magnetic local time, with a significant positional asymmetry about midnight. The magnitude of the temperature enhancement varies with altitude. Within the height range 280 to 940 km, the peak temperature increases by 73%, on average. Thereby a conspicuous increase in the temperature gradient is observed above about 700km altitude. The magnitude of the heating effect also depends on the level of geomagnetic activity. For a decrease in the Dst index by 100 nT, the peak temperature increases by 46%, on average. This rate of increase, however, depends on season and is significantly smaller during winter conditions. A superposed epoch type of averaging procedure is used to obtain mean latitudinal profiles of the temperature enhancement. For an altitude of 500 km, the following mean properties are derived: amplitude K; width at half this peak value deg; distance between equatorward boundary and maximum deg. On average, a decrease in the electron density is observed at the location of the temperature enhancement, at least at 500 km altitude. At the same time, a moderate increase in the zonal ion drift speed is recorded at this location. During larger geomagnetic storms, the latitudinal profile of the temperature enhancement assumes a more step-function-like shape, with a broad increase in electron temperature poleward from the equatorial edge of the electron temperature enhancement. Also the heating effects may extend to very low latitudes (less than 35° invariant latitude). And residual heating effects are observed long after the storm-substorm activity has ceased. The results obtained in this study should prove useful for both empirical and theoretical modeling of the nightside subauroral ionosphere.

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Electron temperatures during rapid subauroral ion drift events

Cited by 17 publications

References 10 publications

Steve: The Optical Signature of Intense Subauroral Ion Drifts

Steve: The Optical Signature of Intense Subauroral Ion Drifts

STEVE and the Picket Fence: Evidence of Feedback‐Unstable Magnetosphere‐Ionosphere Interaction

Subauroral electron temperature enhancement in the nighttime ionosphere

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