scholarly journals Seasonal and longitudinal variation of large-scale topside equatorial plasma depletions

2005 ◽  
Vol 110 (A12) ◽  
Author(s):  
M. A. Hei ◽  
R. A. Heelis ◽  
J. P. McClure
Keyword(s):  
Large Scale ◽  
Longitudinal Variation ◽  
Plasma Depletions

Longitudinal variation in macroinvertebrate assemblages below a large-scale hydroelectric dam

Hydrobiologia ◽  
2015 ◽  
Vol 755 (1) ◽  
pp. 13-26 ◽  
Author(s):  
C. R. Holt ◽  
D. Pfitzer ◽  
C. Scalley ◽  
B. A. Caldwell ◽  
P. I. Capece ◽  
...  
Keyword(s):  
Large Scale ◽  
Longitudinal Variation ◽  
Macroinvertebrate Assemblages ◽  
Hydroelectric Dam

scholarly journals Generation of large-scale equatorial F-region plasma depletions during lowrange spread-F season

2004 ◽  
Vol 22 (1) ◽  
pp. 15-23 ◽  
Author(s):  
Y. Sahai ◽  
P. R. Fagundes ◽  
J. R. Abalde ◽  
A. A. Pimenta ◽  
J. A. Bittencourt ◽  
...  
Keyword(s):  
Large Scale ◽  
Ionospheric Plasma ◽  
Geomagnetic Storms ◽  
Atmospheric Composition ◽  
F Region ◽  
Range Type ◽  
June Solstice ◽  
Radio Signature ◽  
Spread F ◽  
Plasma Depletions

Abstract. All-sky imaging observations of the F-region OI 630nm nightglow emission allow us to visualize large-scale equatorial plasma depletions, generally known as trans-equatorial plasma bubbles. Strong range type spread-F is the radio signature of these (magnetically) north-south aligned plasma depletions. An extensive database of the OI 630nm emission all-sky imaging observations has been obtained at Cachoeira Paulista (22.7°S, 45.0°W; dip latitude ∼16°S), Brazil, between the years 1987 and 2000. An analysis of these observations revealed that relatively few large-scale ionospheric plasma depletions occur during the months of May to August (southern winter, June solstice) in the Brazilian sector. Of the few that are observed during these months, some occur in association with geomagnetic storms and some do not. In this paper, a detailed analysis of the events when large-scale ionospheric plasma depletions were initiated and evolved during the June solstice periods are presented and discussed.Key words. Atmospheric composition and chemistry (airglow and aurora). Ionosphere (equatorial ionosphere; ionospheric irregularities)

scholarly journals Rocket and radar investigation of background electrodynamics and bottom-type scattering layers at the onset of equatorial spread <i>F</i>

2006 ◽  
Vol 24 (5) ◽  
pp. 1387-1400 ◽  
Author(s):  
D. L. Hysell ◽  
M. F. Larsen ◽  
C. M. Swenson ◽  
A. Barjatya ◽  
T. F. Wheeler ◽  
...  
Keyword(s):  
Electric Fields ◽  
Large Scale ◽  
Layer Structure ◽  
Horizontal Structure ◽  
Bottom Type ◽  
Chemical Release ◽  
Spread F ◽  
Density Vector ◽  
Plasma Depletions ◽  
Electron Density Profiles

Abstract. Sounding rocket experiments were conducted during the NASA EQUIS II campaign on Kwajalein Atoll designed to elucidate the electrodynamics and layer structure of the postsunset equatorial F region ionosphere prior to the onset of equatorial spread F (ESF). Experiments took place on 7 and 15 August 2004, each comprised of the launch of an instrumented and two chemical release sounding rockets. The instrumented rockets measured plasma number density, vector electric fields, and other parameters to an apogee of about 450 km. The chemical release rockets deployed trails of trimethyl aluminum (TMA) which yielded wind profile measurements. The Altair radar was used to monitor coherent and incoherent scatter in UHF and VHF bands. Electron density profiles were also measured with rocket beacons and an ionosonde. Strong plasma shear flow was evident in both experiments. Bottom-type scattering layers were observed mainly in the valley region, below the shear nodes, in westward-drifting plasma strata. The layers were likely produced by wind-driven interchange instabilities as proposed by Kudeki and Bhattacharyya (1999). In both experiments, the layers were patchy and distributed periodically in space. Their horizontal structure was similar to that of the large-scale plasma depletions that formed later at higher altitude during ESF conditions. We argue that the bottom-type layers were modulated by the same large-scale waves that seeded the ESF. A scenario where the large-scale waves were themselves produced by collisional shear instabilities is described.

Solar cycle effects on large scale equatorial F-region plasma depletions

1999 ◽  
Vol 24 (11) ◽  
pp. 1477-1480 ◽  
Author(s):  
Y. Sahai ◽  
P.R. Fagundes ◽  
J.A. Bittencourt
Keyword(s):  
Solar Cycle ◽  
Large Scale ◽  
F Region ◽  
Plasma Depletions ◽  
Region Plasma

Some comments about observations and image processing of comet 29P/Schwassmann-Wachmann 1

1999 ◽  
Vol 173 ◽  
pp. 243-248
Author(s):  
D. Kubáček ◽  
A. Galád ◽  
A. Pravda
Keyword(s):  
Image Processing ◽  
Large Scale ◽  
Harvard College ◽  
Oak Ridge ◽  
Large Scale Structures ◽  
Short Period Comet ◽  
Short Period ◽  
Scale Structures ◽  
Harvard College Observatory ◽  
Period Comet

AbstractUnusual short-period comet 29P/Schwassmann-Wachmann 1 inspired many observers to explain its unpredictable outbursts. In this paper large scale structures and features from the inner part of the coma in time periods around outbursts are studied. CCD images were taken at Whipple Observatory, Mt. Hopkins, in 1989 and at Astronomical Observatory, Modra, from 1995 to 1998. Photographic plates of the comet were taken at Harvard College Observatory, Oak Ridge, from 1974 to 1982. The latter were digitized at first to apply the same techniques of image processing for optimizing the visibility of features in the coma during outbursts. Outbursts and coma structures show various shapes.

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