Nonneutral and quasi‐neutral diffusion of weakly ionized multiconstituent plasma

Hill, R. J.

doi:10.1029/ja083ia03p00989

Cited by 68 publications

(85 citation statements)

References 4 publications

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“…When only positive molecular ions are present, these plasma waves have the same wavelength and decay characteristics as the viscosity waves (this is the case of Schmidt number (S)=1, see e.g. Hill, 1978). When negative ions are present, the electron diffusivity is increased and shorter period diffusion waves are needed to match the radar Bragg scale (the case of S 1).…”

Section: Turbulencementioning

confidence: 99%

“…This line also indicates electron diffusivity in the case when only positive molecular ions are present. The dashed line indicates a factor 3 increase in electron diffusivity such as would be produced if the ratio of negative-ions to electrons ( ) is 2 (Hill, 1978). Solid and dashed lines in the other panels show calculated values based on these two diffusivity profiles.…”

Section: Turbulencementioning

confidence: 99%

“…At mesospheric heights, refractive index fluctuations due to fluctuations in electron density dominate those which, in theory, could be due to neutral temperature, density or humidity fluctuations. Turbulent fluctuations in neutral density are expected at scale sizes of a few meters or more and these can be expected to lead to similar fluctuations in ion and electron density, at least during daylight or in the upper mesosphere, and so provide at least a qualitatively possible explanation for the observed radar echoes (Hill, 1978). However, it was not expected that turbulent structures would be present in the electron density in the upper mesosphere at shorter scale sizes than a few meters, due to rapid damping by the high viscosity prevailing at those heights (see, e.g.…”

Section: Introductionmentioning

confidence: 96%

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Infrasound - the cause of strong Polar Mesosphere Winter Echoes?

et al. 2006

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Abstract. The ESRAD 52-MHz and the EISCAT 224-MHz radars in northern Scandinavia observed thin layers of strongly enhanced radar echoes from the mesosphere (Polar Mesosphere Winter Echoes -PMWE) during a solar proton event in November 2004. Using the interferometric capabilities of ESRAD it was found that the scatterers responsible for PMWE show very high horizontal travel speeds, up to 500 ms −1 or more, and high aspect sensitivity, with echo arrival angles spread over as little as 0.3 • . ESRAD also detected, on some occasions, discrete scattering regions moving across the field of view with periodicities of a few seconds. The very narrow, vertically directed beam of the more powerful EISCAT radar allowed measurements of the spectral widths of the radar echoes both inside the PMWE and from the background plasma above and below the PMWE. Spectral widths inside the PMWE were found to be indistinguishable from those from the background plasma. We propose that scatter from highly-damped ion-acoustic waves generated by partial reflection of infrasonic waves provides a reasonable explanation of the characteristics of the very strong PMWE reported here.

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Section: Turbulencementioning

confidence: 99%

Section: Turbulencementioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

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Infrasound - the cause of strong Polar Mesosphere Winter Echoes?

et al. 2006

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“…We have followed the procedure described in Hill [1978] heating power will give detailed information on electron diffusivity and on aerosol properties. Since the decay time is proportional to the square of the spatial scale involved a joint heating/PMSE experiment should be repeated where the PMSE is observed with a radar operating at larger or smaller wavelengths.…”

Section: Pmsementioning

confidence: 99%

Electron temperature control of PMSE

Rapp

Lübken

2000

Geophysical Research Letters

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Abstract.Recently an artificially induced modulation of polar mesosphere summer echos (PMSE) was observed when the electrons at PMSE altitudes were heated by a ground based heating facility [Chilson et al., 2000]. The PMSE disappeared within a few seconds when the heater was switched on and reappeared within a few seconds when the heater was switched off again. We explain these observations employing a model of electron diffusion in the environment of positive ions and negatively charged aerosols which takes into account enhanced electron temperatures. If the electron temperature equals the neutral gas temperature, electron diffusion is efficiently inhibited due to the multipolar electric field between the aerosols, positive ions, and electrons. If the electron temperature is enhanced, however, the electron diffusivity is increased which compensates the effect of charged aerosols such that spatial structures in the electron gas at scales as small as the radar half wavelength are efficiently destroyed by diffusion. Furthermore, an enhanced electron temperature increases the aerosol charge which supports the decay of electron disturbance through plasma interference effects. The heating experiment has demonstrated that the reduction of electron diffusivity by charged aerosol particles is the underlying physical mechanism for the existence of PMSE.

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“…These structures, in turn, are created by neutral air turbulence in combination with an efficient reduction of electron diffusivity by charged mesospheric ice particles (see e.g. Batchelor, 1959;Hill, 1978;Kelley et al, 1987;Rapp and Lübken, 2003;La Hoz et al, 2006;Varney et al, 2011 …”

Section: Analysis Techniquementioning

confidence: 99%

Statistical characteristics of PMWE observations by the EISCAT VHF radar

Strelnikova¹,

Rapp

2013

Ann. Geophys.

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In the present paper ~ 32.5 h of EISCAT VHF PMWE observations were analyzed with focus on spectral properties like spectral width, doppler shift and spectral shape. Examples from two days of observations with weak and strong polar mesosphere winter echo (PMWE) signals are presented and discussed in detail. These examples reveal a large variability from one case to the other. That is, some features like an observed change of vertical wind direction and spectral broadening can be very prominent in one case, but unnoticeable in the other case. However, for all observations a change of spectral shape inside the layer relative to the incoherent background is noticed

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Nonneutral and quasi‐neutral diffusion of weakly ionized multiconstituent plasma

Cited by 68 publications

References 4 publications

Infrasound - the cause of strong Polar Mesosphere Winter Echoes?

Infrasound - the cause of strong Polar Mesosphere Winter Echoes?

Electron temperature control of PMSE

Statistical characteristics of PMWE observations by the EISCAT VHF radar

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