Interferometry investigations of VHF backscatter from plasma irregularity patches in the nighttime <i>E</i> region using the Chung‐Li radar

Chu, Yen Hsyang; Wang, Chien Ya

doi:10.1029/98ja02329

Cited by 22 publications

(27 citation statements)

References 22 publications

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“…In recent times, several papers have been published concerning nighttime E s plasma irregularity patches (PIPs) at Chung‐Li as detected by VHF radar equipment [see Chu and Wang , 1999; Huang , 2000; Wang and Chu , 2001, and references therein]. For three of the particular events considered for the VHF radar investigations, the Chung‐Li f ‐plots have been examined for possible associations with spread‐ F occurrence.…”

Section: A Comparison With Chung‐li Vhf Radar Resultsmentioning

confidence: 99%

Spread‐F/sporadic E coupling at Chung‐Li, especially for postsunset periods of sunspot maximum years

Bowman

Mortimer

2003

J. Geophys. Res.

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[1] Using ionogram-recorded data, the coupling between spread-F occurrence and enhanced E s blanketing frequencies ( f b E s ) (indicative of f o E s changes), has been investigated for an equatorial-ionospheric-anomaly crest station, Chung-Li, for the postsunset periods of sunspot-maximum years. Apart from the evidence for coupling from inspections of the f-plots alone, for the years analyzed (1981, 1982, 1988, and 1989), statistical results of more significance were found from superposed-epoch analyses. Isolated spread-F events of duration of 2 hours or less which started at or before 2200 LT were used as controls on time series. These series were made up of comparisons between 15-min f-plot f b E s values and interpolated monthly median f b E s values. Evidence for coupling was found for the analyses which involved 97 controls. The evidence in the f-plots for three events involving E s patches, which investigators have examined in some detail using the VHF radar at Chung-Li, suggests that these events are also coupled to isolated spread-F occurrence.

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Section: A Comparison With Chung‐li Vhf Radar Resultsmentioning

confidence: 99%

Spread‐F/sporadic E coupling at Chung‐Li, especially for postsunset periods of sunspot maximum years

Bowman

Mortimer

2003

J. Geophys. Res.

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“…However, if Es irregularities group together in an isolate and confined structure with finite vertical and horizontal dimensions, the echo patterns in azimuth and horizontal planes will be the projections of cross sections of the structure cut by the fan‐like effective antenna beam on the respective planes. In this case the echo patterns in azimuth and horizontal planes will be patch‐like, not striation‐like [ Chu and Wang , 1997, 1999]. Therefore the spatial structure of Es irregularities basically can be inferred from the configurations of echo patterns on the mutual orthogonal planes.…”

Section: Observational Resultsmentioning

confidence: 99%

Three‐dimensional spatial structures of midlatitude type 1 Es irregularities

Chu

Wang

2002

J. Geophys. Res.

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[1] Concurrent type 1 and type 2 radar returns from sporadic E (Es) irregularities detected by the Chung-Li VHF radar are analyzed and discussed in this paper. For the present case the mean Doppler velocities of the type 1 echoes lasting $8 min are between $250 and 302 m/s, smaller than those observed in equatorial and auroral regions. The backscatter from type 1 irregularities is greater than that from type 2 irregularities by $6-8 dB. Interferometry analysis indicates that the echo patterns of the type 1 and type 2 irregularities projected in mutually orthogonal planes are striation-like, strongly suggesting that the plasma structure associated with the irregularities is in a form of thin slab. The plasma slab with thickness of $1-2.5 km locates in the height range from $104 to 107 km. The horizontal extents of the type 1 irregularities in the striation-like echoing region range from 12.7 to 6.8 km in the east-west direction and from at least 7.2 to 5.1 km in the north-south direction. The observational evidences that the slab structure has sharp edges in lateral edges and the type 1 irregularities drift in the meridional direction favor the slab model proposed by Haldoupis et al. [1996] to account for the excitation of the midlatitude type 1 irregularities. However, the other observations, including considerably large zonal extent of type 1 irregularities in the plasma slab and wide coverage of zonal polarization electric field, are unfavorable to the slab model. In addition, we present conclusive evidence in this article to show that the range variation of backscatter from Es irregularities may result directly from the zonal bulk movement of the Es irregularities in the echoing region rather than from the height variation of the irregularities. Therefore great caution should be taken in analyzing the dynamic behavior of Es irregularities from range-time-intensity plot.

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“…The off ⊥B smearing effect may, therefore, explain the double spectral peaks and the spectral broadening found in Fig. 3 of Chu and Wang (1999). Additionally, the altitude smearing effect for low frequency radars is more severe than for high frequency radars.…”

Section: Aspect Sensitivity Of Echoes From Fai Within Horizontal Ionimentioning

confidence: 86%

“…Recent observations of ionospheric FAI include those of Chu andWang (1999), Hysell andBurcham (2000), Urbina et al (2000), Woodman and Chau (2001) and references therein. Middle latitude ionospheric FAI are believed to result from the steep gradient of sporadic E-(Es-) layers and a discussion on various seeding mechanisms can be found in Larsen (2000).…”

Section: Introductionmentioning

confidence: 99%

Aspect sensitivity of VHF echoes from field aligned irregularities in meteor trails and thin ionization layers

et al. 2004

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Abstract. The aspect sensitivity of VHF echoes from field aligned irregularities (FAI) within meteor trails and thin ionization layers is studied using numerical models. Although the maximum power is obtained when a radar is pointed perpendicular to the field line (⊥B), substantial power can be obtained off the ⊥B direction if the ionization trail/layer is thin. When the FAI length along B is 20 m, the power observed 6 • off ⊥B is about 10 db below that perpendicular to the B direction. Meteoric FAI echoes can potentially be used to determine the diffusion rate in the mesopause region. Based on the aspect sensitivity analysis, we conclude that the range spread trail echoes far off ⊥B observed by powerful VHF radars are likely due to overdense meteors. Our simulation also shows that ionospheric FAI echoes can have an altitude smearing effect of about 4 km if the vertical extension of a FAI-layer is around 100 m, which has often been observed at Arecibo. The altitude smearing effect can account for the fact that the Es-layers observed by the Arecibo incoherent scatter radar are typically much narrower than FAI-layers and the occurrence of double spectral peaks around the Es-layer altitude in FAI echoes.

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Interferometry investigations of VHF backscatter from plasma irregularity patches in the nighttime E region using the Chung‐Li radar

Cited by 22 publications

References 22 publications

Spread‐F/sporadic E coupling at Chung‐Li, especially for postsunset periods of sunspot maximum years

Spread‐F/sporadic E coupling at Chung‐Li, especially for postsunset periods of sunspot maximum years

Three‐dimensional spatial structures of midlatitude type 1 Es irregularities

Aspect sensitivity of VHF echoes from field aligned irregularities in meteor trails and thin ionization layers

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