First in‐situ observations of neutral and plasma density fluctuations within a PMSE layer

Lübken, Franz‐Josef; Lehmacher, G. A.; Blix, T. A.; Hoppe, Ulf-Peter; Thrane, E. V.; Cho, John; Swartz, Wesley E.

doi:10.1029/93gl00851

Cited by 64 publications

(46 citation statements)

References 12 publications

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“…Many observations of PMSEs indicate double structures which are narrowly separated in altitude (Czechowsky et al, 1988LuÈ bken et al, 1993;Miller et al, 1993;Ulwick et al, 1993;Inhester et al, 1994). This can also be seen in the altitude pro®les of vertical S/N, Fig.…”

Section: Vertical Structure Of Mse Layersmentioning

confidence: 63%

“…Although the STATE radar and rocket observations, at the same altitude, had a maximum horizontal separation of 10 km (Ulwick et al, 1988), the minimum horizontal separation was 20 km for the MAC/SINE campaign and 13.3 km for the NLC-91 campaign (LuÈ bken et al, 1993); the maximum horizontal separations for the latter two campaigns were in excess of 50 km. Furthermore, given the extremely dynamic nature of MSEs and PMSEs, measurements from any single rocket observation will only be representative of the atmosphere at that particular sampling time and place.…”

Section: Discussionmentioning

confidence: 99%

“…In several instances of double-structure PMSEs, both mechanisms have been cited as being responsible in order to account for the dierences between the natures of the two layers LuÈ bken et al, 1993;Miller et al, 1993;Ulwick et al, 1993). Radar returns from PMSEs that show large aspect sensitivity have been attributed to Fresnel re¯ec-tion, and those that show low aspect sensitivity have been interpreted in terms of backscatter .…”

Section: Discussionmentioning

confidence: 99%

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The small-scale structure of VHF mesospheric summer echo layers observed at mid-latitudes

Hooper

Thomas

1997

Ann. Geophys.

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Abstract. The VHF radar system at Aberystwyth (52X4 N, 4X1 E) has been used to make high-timeresolution, multi-beam observations of mesospheric summer echo layers. These show that the altitude and the sense of vertical movement of the layers can vary over time-scales of minutes and horizontal scales of kilometres. In general, the altitude pro®les of signal-tonoise ratio provide evidence of a bifurcated structure with sharp changes in the horizontal wind vector and vertical velocity, and enhanced spectral width occurring at the bifurcation level. The implications of the smallscale structure for studies of the aspect sensitivity of radar returns are discussed, and the changes in wind®eld at the bifurcation level are compared with`wind corners' observed in rocket studies of the mesosphere at polar latitudes.

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Section: Vertical Structure Of Mse Layersmentioning

confidence: 63%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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The small-scale structure of VHF mesospheric summer echo layers observed at mid-latitudes

Hooper

Thomas

1997

Ann. Geophys.

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“…However, the approach developed here can be applied to the irregularities in the lower ionosphere at high and low latitudes. At least the present theoretical estimates of the spectral form and the rms level of plasma¯uctuations do not seem to contradict experimental results obtained during rocket measurements in the auroral and equatorial lower ionosphere (see, e.g., Rùyrvic and Smith, 1984;Pfa et al, 1984Pfa et al, , 1987aSchlegel, 1992;Gurevich et al, 1996;Ulwick et al, 1993;LuÈ bken et al, 1993). It should be noted that in some of the mentioned works (Pfa et al, 1984(Pfa et al, , 1987a plasma instabilities are proposed as basic mechanisms for the generation of ionospheric irregularities while in others a role of neutral turbulence in the formation of plasma irregularities is admitted (R yrvic and Smith, 1984;Schlegel, 1992;Gurevich et al, 1996;Ulwick et al, 1993;LuÈ bken et al, 1993).…”

Section: Discussionmentioning

confidence: 49%

On the spectrum of mid-latitude sporadic-<i>E</i> irregularities

Kyzyurov

2000

Ann. Geophys.

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Abstract. We discuss the creation of mid-latitude sporadic-E plasma irregularities (with length-scales smaller than sporadic layer thickness) by the neutral atmosphere turbulence. Using¯uid equations, the relation between plasma density¯uctuations and the velocity ®eld of neutrals is derived. After a brief discussion of the relevant neutral turbulence, the analytical expression for the power spectrum of plasma irregularities is obtained. This expression allows a power-law type of experimental irregularity spectra (the spectral index depends on sporadic-E characteristics) and possible departures in detail of the irregularity spectra from the power-law form to be explained. In addition, it allows us to make estimates of length-scales at which such departures must occur.

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“…Plasma¯uctuations caused by neutral turbulence can account for some of the PMSE signatures that have been observed; however, LuÈ bken et al (1993) have convincingly shown that PMSE can exist at altitudes where no neutral turbulence is present. Therefore we must additionally consider mechanisms for generating PMSE that do not directly require turbulence.…”

Section: Introductionmentioning

confidence: 99%

Frequency domain interferometry mode observations of PMSE using the EISCAT VHF radar

Chilson

Kirkwood

Häggström

2001

Annales Geophysicae

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Abstract. During the summer of 1997 investigations into the nature of polar mesosphere summer echoes (PMSE) were conducted using the European incoherent scatter (EISCAT) VHF radar in Norway. The radar was operated in a frequency domain interferometry (FDI) mode over a period of two weeks to study the frequency coherence of the returned radar signals. The operating frequencies of the radar were 224.0 and 224.6 MHz. We present the ®rst results from the experiment by discussing two 4-h intervals of data collected over two consecutive nights. During the ®rst of the two days an enhancement of the FDI coherence, which indicates the presence of distinct scattering layers, was found to follow the lower boundary of the PMSE. Indeed, it is not unusual to observe that the coherence values are peaked around the heights corresponding to both the lower-and upper-most boundaries of the PMSE layer and sublayers. A Kelvin±Helmholtz mechanism is oered as one possible explanation for the layering structure. Additionally, our analysis using range-timepseudocolor plots of signal-to-noise ratios, spectrograms of Doppler velocity, and estimates of the positions of individual scattering layers is shown to be consistent with the proposition that upwardly propagating gravity waves can become steepened near the mesopause.

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First in‐situ observations of neutral and plasma density fluctuations within a PMSE layer

Cited by 64 publications

References 12 publications

The small-scale structure of VHF mesospheric summer echo layers observed at mid-latitudes

The small-scale structure of VHF mesospheric summer echo layers observed at mid-latitudes

On the spectrum of mid-latitude sporadic-<i>E</i> irregularities

Frequency domain interferometry mode observations of PMSE using the EISCAT VHF radar

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First in‐situ observations of neutral and plasma density fluctuations within a PMSE layer

Cited by 64 publications

References 12 publications

The small-scale structure of VHF mesospheric summer echo layers observed at mid-latitudes

The small-scale structure of VHF mesospheric summer echo layers observed at mid-latitudes

On the spectrum of mid-latitude sporadic-&lt;i&gt;E&lt;/i&gt; irregularities

Frequency domain interferometry mode observations of PMSE using the EISCAT VHF radar

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On the spectrum of mid-latitude sporadic-<i>E</i> irregularities