The generation of non aspect sensitive plasma density irregularities by field aligned drifts in the lower ionosphere

Robinson, T. R.; Schlegel, K.

doi:10.1007/s00585-000-0799-y

Cited by 3 publications

(3 citation statements)

References 21 publications

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“…Therefore, the gradient-drift effect cannot be considered the controlling source of electron heating. Similarly, the theory by Robinson and Schlegel [2000] on the generation of non-aspect-sensitive plasma density irregularities by fieldaligned drifts is unlikely to explain electron heating because the dependence on the field-aligned drift direction would make the highly consistent dependence on E c unlikely.…”

Section: Introductionmentioning

confidence: 99%

On the generation of large wave parallel electric fields responsible for electron heating in the high‐latitude E region

Bahcivan

Cosgrove

2010

J. Geophys. Res.

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[1] The sources of parallel electric fields (E k ) to explain E region electron heating measurements made by incoherent scatter radars have not been resolved. This paper considers the effect of electron density gradients parallel to the geomagnetic field (r k n) on the Farley-Buneman instability and the resulting change in wave dE k . The dispersion relation including the r k n effect is derived and solved for a set of wave vectors at marginal stability. It is shown that r k n with scales of several kilometers enable propagation of 50 m or longer wavelength waves at large angles (up to 5°) from perpendicularity to the geomagnetic field. The fact that kilometric scales of r k n were previously shown to occur during strong electrojet and that they coincide statistically well with the altitudes of strongest electron heating support the role of these long-wavelength waves in electron heating. Furthermore, unlike the gradient-drift instability, the r k n effect contributes to the growth of the waves with the proper k k sign regardless of the direction of the convection electric field E c ; this makes the r k n effect eligible as a source of electron heating, resulting in the consistent increase of electron temperature with the magnitude of E c . Moreover, it is shown that the inclusion of the r k n effect reduces the discrepancy between the theoretically required perpendicular electric field turbulence (to raise the electron temperature to the measured values) and the in situ rocket measurements.Citation: Bahcivan, H., and R. Cosgrove (2010), On the generation of large wave parallel electric fields responsible for electron heating in the high-latitude E region,

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Section: Introductionmentioning

confidence: 99%

On the generation of large wave parallel electric fields responsible for electron heating in the high‐latitude E region

Bahcivan

Cosgrove

2010

J. Geophys. Res.

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“…We hence conclude that our observations can likely not be explained by regular auroral backscatter. We note, however, that we can also not exclude the mechanism(s) proposed by Robinson and Schlegel [2000]. However, our current database does not allow us to check their proposal of electron drifts aligned with the geomagnetic field, neither are we in the position to speculate about the additional nonlinear feedback processes that are required in their work to shift the plasma waves into the right wavelength range.…”

Section: Discussionmentioning

confidence: 68%

“…However, after detailed discussion, Rüster and Schlegel [1999] concluded that their observations could not be explained by these mechanisms and that other alternative processes need to be invoked. One such alternative was presented by Robinson and Schlegel [2000], who proposed a new instability mechanism based on field‐aligned electron drifts with additional positive feedback from electron collisional heating. Realizing that their theory predicted, however, only waves in excess of a few tens of meters, Robinson and Schlegel [2000] further speculated about additional nonlinear feedback mechanisms that could possibly shift the the wavelength range of the instability to the required value of ∼3 m. However, since the observations of Rüster and Schlegel [1999] were never repeated such that no additional observational constraints are available, it remains an open question whether or not the mechanisms proposed by Robinson and Schlegel [2000] do occur and lead to detectable radar echoes.…”

Section: Introductionmentioning

confidence: 99%

Localized mesosphere-stratosphere-troposphere radar echoes from theEregion at 69°N: Properties and physical mechanisms

et al. 2011

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[1] We present the first observations, to our knowledge, of a new class of high-latitude mesosphere-stratosphere-troposphere radar echoes from the E region as observed with the Arctic Lidar Observatory for Middle Atmosphere Research wind radar during the period [2004][2005][2006][2007][2008]. These echoes occur primarily during the summer months and in the altitude range from 93 to 114 km, with a pronounced peak of maximum occurrence at about 100 km. The echoes are rather short with typical durations of ∼20 min, with some examples lasting as long as 3 h. The echoes typically cover only a few hundred meters in the vertical and show both small Doppler velocities (±1-2 m/s) as well as very narrow spectral widths (just a few meters per second when converted to Doppler velocities). The echoes are highly aspect sensitive indicative of a specular-scattering mechanism and reveal a distinct diurnal variation with maxima of occurrence around noon and midnight. The latter is related to the semidiurnal tidal components of the zonal and meridional wind where times of occurrence correspond to large values of corresponding vertical wind shears. Considering possible physical mechanisms, turbulence with large Schmidt number scatter is likely ruled out as is auroral backscatter. Finally, a strong case for a close correspondence of the echoes to sporadic E layers is presented on the basis of comparisons to ionosonde data, occurrence patterns of sporadic layers, simultaneous and common volume lidar measurements of a sporadic Fe layer, as well as simultaneous measurements of sporadic E layers with the European Incoherent Scatter UHF radar at a horizontal distance of 130 km. Applying the theory of partial reflections to the observed electron density gradients, we are able to demonstrate that the observed echo strengths can likely be explained on the basis of this scattering mechanism.Citation: Rapp, M., L. Leitert, R. Latteck, M. Zecha, P. Hoffmann, J. Höffner, U.-P. Hoppe, C. La Hoz, and E. V. Thrane (2011), Localized mesosphere-stratosphere-troposphere radar echoes from the E region at 69°N: Properties and physical mechanisms,

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D region HF radar echoes associated with energetic particle precipitation and pulsating aurora

Milan

Hosokawa²,

Lester³

et al. 2008

Ann. Geophys.

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Abstract. identified a class of narrow, slow-moving HF radar backscatter echoes which originate between altitudes of 80 and 100 km, the ionospheric D-and lower E-regions. These echoes appeared to be associated with the occurrence of pulsating aurora, which are known to be created by energetic electrons capable of penetrating to D region altitudes. In this study we show that these echoes are observed in tandem with enhancements in cosmic noise absorption (auroral absorption), additional evidence that energetic (>30 keV) particle precipitation is responsible for generating the irregularities from which a radar can scatter. In addition, we show that the D region backscatter echoes occur predominantly in the post-midnight sector during substorm recovery phase, in common with auroral absorption events and pulsating aurora.

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The generation of non aspect sensitive plasma density irregularities by field aligned drifts in the lower ionosphere

Cited by 3 publications

References 21 publications

On the generation of large wave parallel electric fields responsible for electron heating in the high‐latitude E region

On the generation of large wave parallel electric fields responsible for electron heating in the high‐latitude E region

Localized mesosphere-stratosphere-troposphere radar echoes from theEregion at 69°N: Properties and physical mechanisms

D region HF radar echoes associated with energetic particle precipitation and pulsating aurora

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