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  • Other Sources  (5)
  • 1990-1994  (5)
  • 1993  (5)
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  • 1990-1994  (5)
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  • 1
    Publication Date: 2019-07-13
    Description: We report mesospheric electronic field structure in the vicinity of noctilucent clouds (NLC) and polar mesospheric summer echoes (PMSEs) measured on the DECIMALS-B rocket payload launched during the international rocket-radar campaign NLC-91 from Esrange, Sweden on August 10, 1991. Unusually large vertical E- fields, E(sub Z), about 100-300 mV/m on ascent and greater than 1 V/m on descent were detected at 82.5-84.5 km. The region of the large E(sub Z) was clearly limited by the NLC layer on the bottom and by the distinctly separated PMSE layer on the top. A narrow negative peak in the E(sub Z) height profile observed on ascent in the lower part of the NLC layer was apparently caused by the interaction of the field mill with impacting NLC particles possibly carrying negative charge. If the impact signature is due to single particles, their size is estimated to at least 0.5 microns and their concentration about 10(exp -4)/cu cm locally. Based on the light-scattering properties of NLC such massive particles can only be a minor part of the NLC population.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 20; 20; p. 2299-2302
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  • 2
    Publication Date: 2019-07-13
    Description: The Cornell University Portable Radar Interferometer (CUPRI) provided nearly continuous monitoring of the mesosphere above Esrange, Sweden during the noctilucent cloud rocket and radar campaign of the summer of 1991 (NLC-91). CUPRI probed the mesosphere above Esrange from 78 to 91 km altitude with 300-meter resolution and was sensitive to the enhanced Polar Mesospheric Summer Echoes (PMSE) that occur in the same altitude range as NLC formations. Out of the total of 264 hours of CUPRI observation time, PMSE were present for 140 hours. Rocket Salvo A was flown on the night of August 9-10 into an NLC event that occurred simultaneously with a thin and weakening PMSE layer. High-resolution Doppler spectrograms of this PMSE event revealed sawtooth-like discontinuities at approximately 83 km altitude, which we interpret to be a distorted partial reflection layer which was advected across the radar beam.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 20; 20; p. 2287-2290
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  • 3
    Publication Date: 2019-07-13
    Description: During the first rocket sequence (called Salvo B) of the NLC-91 campaign, the Cornell University Portable Radar Interferometer (CUPRI) observed two simultaneously occurring layers of Polar Mesophere Summer Echoes (PMSE). during the time of the Turbo B flight, the high time-resolution CUPRI Doppler spectra exhibited sawtooth-like discontinuities in the lower layer which we interpret to be a distorted partial reflection layer which was advected across the radar beam. The upper layer, on the other hand, appeared to be caused by turbulent scatter and we estimate the turbulence energy dissipation rate in the upper layer at the time of the Turbo B flight to have been approximately 0.04 W/kg. Futhermore, a shift in the antenna beam direction from vertical to 8 deg off zenith revealed an aspect sensitivity of approximately 5 dB in the lower layer but none in the upper layer. We conclude that, at this particular time, turbulent scatter was responsible for the upper layer while some form of partial reflection was dominant in the lower layer.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 20; 20; p. 2291-2294
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  • 4
    Publication Date: 2019-07-13
    Description: On the night of August 9-10, 1991, two rocket payloads were launched into simultaneously occurring noctilucent clouds (NLC) and polar mesospheric summer echoes (PMSE) above Esrange, a third rocket payload was launched into a NLC where a PMSE was detected 5 minutes later above Esrange, in Sweden as part of the NLC-91 campaign. An aim of this experiment was to compare the vertical structures and locations of the NLC and PMSE events. To this end, in-situ optical photometers and particle impact sensors were used to measure the altitude and vertical structure of the NLC layer, while the Cornell University portable radar interferometer (CUPRI) was used to probe the PMSE. Although this comparison is complicated by the horizontal separations between the in-situ measurements and the radar volume, and low electron densities which reduced the overall radar reflectivity, we conclude that the PMSE layer in the CUPRI radar volume remained above the NLC layer detected by the in-situ instruments by 300 to 2000 m throughout the experiment. We interpret this result as supporting the view that PMSE are more likely to result from the presence of aerosols smaller than the ones optically detectable as NLCs.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 20; 24; p. 2845-2848
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  • 5
    Publication Date: 2019-07-13
    Description: The Cornell University Portable Radar Interferometer (CUPRI) observed two extremely strong layers of Polar Mesosphere Summer Mesosphere (PMSE) thirty minutes prior to the launch of Salvo C of the NLC-91 campaign. The lower layer exhibited a S/N ratio of 42 dB (the second strongest event of NLC-91), vertical velocities of a few m/s, and a narrow spectral width, suggesting that it was the result of partial reflections. The upper layer, in contrast, exhibited sinusoidal structures in vertical velocity with peak amplitudes greater than +/- 10 m/s and wide spectral widths. These structures were observed to grow and steepen with altitude until they broke and produced turbulent radar scattering. We conclude that the rapid rate of growth of hte wave with altitude was the result of a depressed mesopause temperature and a nearly adiabatic temperature gradient at PMSE heights and that the simultaneous measurement of both a low mesopause temperature and strong PMSE supports recent theories that find the presence of charged aerosols to be the key to the unique radar cross sections associated with PMSE.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 20; 20; p. 2295-2298
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