The temporal evolution of the ionospheric signatures of subauroral ion drifts

Moffett, R. J.; Heelis, R. A.; Sellek, R.; Bailey, G. J.

doi:10.1016/0032-0633(92)90007-b

“…where x O Y x NO are the O and NO concentrations, respectively, k O and k NO are the parallel temperatures of the ion gases and c O and c NO the perpendicular temperatures; here O 2 has been neglected, since it appears to play a minor role in the molecular ion abundance during SAID events (Moett et al, 1992a). This average ion temperature enters into the electron-ion heat transfer term in the heat balance equations.…”

Section: Model Runs and Resultsmentioning

confidence: 99%

“…Using the observed ion drifts as inputs, mathematical models of the ionosphere have been used to study the causes of the observed signatures of SAID (Sellek et al, , 1992Moett et al, 1991Moett et al, , 1992aMoett et al, ,b, 1993KoÈ roÈ smezey et al, 1992;Heelis et al, 1993). Elevated and anisotropic ion temperatures, depletion of electron density, changes in ion composition, enhanced ®eld-aligned plasma¯ows and the behaviour of H and He in the topside ionosphere have been modelled for various SAID conditions.…”

Section: A1mentioning

confidence: 99%

Electron temperatures during rapid subauroral ion drift events

Moffett

¹

,

Ennis

²

,

Bailey

³

et al. 1998

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Abstract. Examples of data from DE-2 satellite instruments are presented. These illustrate the behaviour of plasma parameters in the F-region and adjacent topside ionosphere during rapid sub-auroral ion drift (SAID) events. In particular, a variety of behaviours of the electron temperature e is demonstrated, both within and equatorward of the SAID region. The Sheeld University plasmasphere-ionosphere model (SUPIM) is used to perform calculations in which a model SAID is applied to a plasma¯ux tube. The model results indicate that strongly elevated ion temperature (a recognised signature of SAID events) is on occasion sucient to raise e to observed values by ion-electron heat transfer. On other occasions, an additional heat source is required. It is suggested that such a source for the electron gas may be due to interaction between the ring current and the plasmasphere at high altitudes. The magnitude of the downward heat¯ux is consistent with that necessary to produce sub-auroral red arcs. The resulting strongly heated electron gas causes vibrational excitation of molecular nitrogen in the thermosphere.

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“…The Moett et al, 1992a) but a net decrease in x e in the F-region. The depth of the trough is emphasised by being embedded in the evening sector mid-latitude trough , which may be substantially formed by plasma stagnation (Spiro et al, 1978).…”

Section: Observations Of Saidmentioning

confidence: 99%

Electron temperatures during rapid subauroral ion drift events

Moffett

¹

,

Ennis

²

,

Bailey

³

et al. 1998

View full text Add to dashboard Cite

Abstract. Examples of data from DE-2 satellite instruments are presented. These illustrate the behaviour of plasma parameters in the F-region and adjacent topside ionosphere during rapid sub-auroral ion drift (SAID) events. In particular, a variety of behaviours of the electron temperature e is demonstrated, both within and equatorward of the SAID region. The Sheeld University plasmasphere-ionosphere model (SUPIM) is used to perform calculations in which a model SAID is applied to a plasma¯ux tube. The model results indicate that strongly elevated ion temperature (a recognised signature of SAID events) is on occasion sucient to raise e to observed values by ion-electron heat transfer. On other occasions, an additional heat source is required. It is suggested that such a source for the electron gas may be due to interaction between the ring current and the plasmasphere at high altitudes. The magnitude of the downward heat¯ux is consistent with that necessary to produce sub-auroral red arcs. The resulting strongly heated electron gas causes vibrational excitation of molecular nitrogen in the thermosphere.

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“…SAPS can deepen the F region trough density (e.g., Smiddy et al, 1977;Maynard, 1978;Spiro et al, 1978;Anderson et al, 1991Anderson et al, , 2001Foster et al, 2007), enhance the electron temperature (e.g., Wang and Lühr, 2013;Mishin, 2013), contribute to the ion upflow (e.g., Yeh and Foster, 1990;Anderson et al, 1991;Moffett et al, 1992;Erickson et al, 2010;Wang and Lühr, 2013), and induce strong scintillations of UHF (ultra-high frequency) and L-band signals (e.g., Basu et al, 2008). Recent studies have disclosed that SAPS can cause westward wind jets and air density anomalies, which peak at the same location (e.g., Wang et al, 2012a, b;Wang et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

The spatial distribution of region 2 field-aligned currents relative to subauroral polarization stream

Wang

¹

,

Lühr

²

,

Ridley

³

et al. 2014

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Abstract. To test the current-generation model of subauroral polarization stream (SAPS), we have investigated the relative positions of field-aligned currents (FACs) with respect to SAPS in a statistical way by using CHAMP (CHAllenging Minisatellite Payload) and DMSP (Defense Meteorological Satellite Program) satellite observations as well as model simulations. Comparative studies have been performed for consecutive CHAMP observations in different magnetic local time (MLT) sectors with respect to SAPS. The latitude of the peak westward zonal wind deduced from CHAMP measurements has been used to represent the location of the SAPS peak. Both the density and the sheet current strength of R2 (region 2) FACs are enhanced when SAPS occur. Subsequently R2 FACs decay in intensity and correspondingly the centers retreat poleward. The latitudes of the center of the R2 FAC, small-and medium-scale FACs, and SAPS shift equatorward with increasing MLT. The SAPS peaks are located between R2 and R1 (region 1) FAC peaks in all MLT bins under study. The SAPS peaks are closer to R2 centers in the later MLT sectors. The peaks of small-and mediumscale FACs are located poleward of SAPS, mainly in the upward R1 FACs region. The upward R1 FACs are partly closed by the downward R1 FACs in the dawn-morning sector. Based on model simulation, when R2 shifts equatorward to the subauroral region, the plasma flow also shifts equatorward with its peak located poleward of that of R2 FACs. Both the model and observations provide evidence that SAPS behave as caused by a magnetospheric current source.

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The temporal evolution of the ionospheric signatures of subauroral ion drifts

Cited by 30 publications

References 18 publications

Electron temperatures during rapid subauroral ion drift events

Electron temperatures during rapid subauroral ion drift events

Electron temperatures during rapid subauroral ion drift events

The spatial distribution of region 2 field-aligned currents relative to subauroral polarization stream

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