scholarly journals First observation of presunset ionospheric F region bottom‐type scattering layer

2017 ◽  
Vol 122 (3) ◽  
pp. 3788-3797 ◽  
Author(s):  
Guozhu Li ◽  
Baiqi Ning ◽  
M. A. Abdu ◽  
Weixing Wan ◽  
Chi Wang ◽  
...  
Keyword(s):  
Scattering Layer ◽  
Bottom Type ◽  
F Region

scholarly journals Coherent backscatter radar imaging in Brazil: large-scale waves in the bottomside F-region at the onset of equatorial spread <I>F</I>

2008 ◽  
Vol 26 (11) ◽  
pp. 3355-3364 ◽  
Author(s):  
F. S. Rodrigues ◽  
D. L. Hysell ◽  
E. R. de Paula
Keyword(s):  
Large Scale ◽  
Imaging Technique ◽  
Radar Imaging ◽  
Shear Instability ◽  
Wide Field ◽  
Bottom Type ◽  
F Region ◽  
Type Layer ◽  
Spread F ◽  
Coherent Backscatter

Abstract. The 30 MHz coherent backscatter radar located at the equatorial observatory in São Luís, Brazil (2.59° S, 44.21° W, −2.35° dip lat) has been upgraded to perform coherent backscatter radar imaging. The wide field-of-view of this radar makes it well suited for radar imaging studies of ionospheric irregularities. Radar imaging observations were made in support to the spread F Experiment (SpreadFEx) campaign. This paper describes the system and imaging technique and presents results from a bottom-type layer that preceded fully-developed radar plumes on 25 October 2005. The radar imaging technique was able to resolve decakilometric structures within the bottom-type layer. These structures indicate the presence of large-scale waves (~35 km) in the bottomside F-region with phases that are alternately stable and unstable to wind-driven gradient drift instabilities. The observations suggest that these waves can also cause the initial perturbation necessary to initiate the Generalized Rayleigh-Taylor instability leading to spread F. The electrodynamic conditions and the scale length of the bottom-type layer structures suggest that the waves were generated by the collisional shear instability. These results indicate that monitoring bottom-type layers may provide helpful diagnostics for spread F forecasting.

scholarly journals Characteristics of very large aspect angle E-region coherent echoes at 933 MHz

1997 ◽  
Vol 15 (1) ◽  
pp. 54-62 ◽  
Author(s):  
B. J. Jackel ◽  
D. R. Moorcroft ◽  
K. Schlegel
Keyword(s):  
Phase Velocity ◽  
Scattering Layer ◽  
Aspect Angle ◽  
Ion Drift ◽  
Phase Velocities ◽  
F Region ◽  
E Region ◽  
Inversion Techniques ◽  
Coherent Backscatter ◽  
Uhf Radar

Abstract. The EISCAT UHF radar system was used to study the characteristics of E-region coherent backscatter at very large magnetic aspect angles (5–11°). Data taken using 60 μs pulses during elevation scans through horizontally uniform backscatter permitted the use of inversion techniques to determine height profiles of the scattering layer. The layer was always singly peaked, with a mean height of 104 km, and mean thickness (full width at half maximum) of 10 km, both independent of aspect angle. Aspect sensitivities were also estimated, with the Sodankylä-Tromsø link observing 5 dB/degree at aspect angles near 5°, decreasing to 3 dB/degree at 10° aspect angle. Observed coherent phase velocities from all three stations were found to be roughly consistent with LOS measurements of a common E-region phase velocity vector. The E-region phase velocity had the same orientation as the F-region ion drift velocity, but was approximately 50% smaller in magnitude. Spectra were narrow with skewness of about +1 (for negative velocities), increasing slightly with aspect angle.

scholarly journals Bottom-type scattering layers and equatorial spread <i>F</i>

2004 ◽  
Vol 22 (12) ◽  
pp. 4061-4069 ◽  
Author(s):  
D. L. Hysell ◽  
J. Chun ◽  
J. L. Chau
Keyword(s):  
Large Scale ◽  
Coherent Scattering ◽  
Plasma Waves ◽  
Equatorial Ionosphere ◽  
Bottom Type ◽  
Radar Images ◽  
F Region ◽  
Type Layer ◽  
Spread F ◽  
Gradient Drift

Abstract. Jicamarca radar observations of bottom-type coherent scattering layers in the post-sunset bottomside F-region ionosphere are presented and analyzed. The morphology of the primary waves seen in radar images of the layers supports the hypothesis of kudeki+bhattacharyya-1999 that wind-driven gradient drift instabilities are operating. In one layer event when topside spread F did not occur, irregularities were distributed uniformly in space throughout the layers. In another event when topside spread F did eventually occur, the irregularities within the pre-existing bottom-type layers were horizontally clustered, with clusters separated by about 30km. The same horizontal periodicity was evident in the radar plumes and large-scale irregularities that emerged later in the event. We surmise that horizontal periodicity in bottom-type layer irregularity distribution is indicative of large-scale horizontal waves in the bottomside F-region that may serve as seed waves for large-scale Rayleigh Taylor instabilities. Key words. Ionosphere (equatorial ionosphere; ionospheric irregularties; plasma waves and instabilities)

High Latitude F-Region Drift Studies.

1986 ◽  
Author(s):  
Bodo W. Reinisch ◽  
Jurgen Buchau ◽  
Edward J. Weber ◽  
Claude G. Dozois ◽  
Klaus Bibl
Keyword(s):  
High Latitude ◽  
F Region
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