Structures in sporadic‐<i>E</i> observed with an impedance probe during the SEEK Campaign: Comparisons with neutral‐wind and radar‐echo observations

Yamamoto, Masayuki; Ono, Takayuki; Oya, Hiroshi; Tsunoda, Roland T.; Larsen, M. F.; Fukao, S.; Yamamoto, Mamoru

doi:10.1029/98gl00709

Cited by 42 publications

(37 citation statements)

References 7 publications

(5 reference statements)

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“…Woodman et al (1991) and later had explained the generation of these echoes by atmospheric gravity waves modulating the sporadic E-layers (E s ) in such a way so as to make them locally unstable by the gradient drift instability. However, this theory could not fully explain the experimental observations made by sounding rocket campaigns from Japan (Sporadic-E Experiment over Kyushu=SEEK; Fukao et al, 1998;Yamamoto et al, 1998). This theory also failed to explain the observations of multiple striations within the QP echoes and their semidiurnal behavior (Pan and Tsunoda, 1999).…”

Section: Introductionmentioning

confidence: 64%

Three-dimensional tracking of mid-latitude quasi-periodic E-region echoes observed with the Chung-Li VHF radar

Chen

Röttger

et al. 2005

Ann. Geophys.

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Abstract. This paper presents observations of low-altitude mid-latitude E-region irregularities obtained with the 52-MHz Chung-Li VHF radar. These are carried out in the interferometer mode to investigate the behavior of these irregularities over time and space. The observations presented here show the characteristics of type-II echoes noted by a negative slope, i.e. they are approaching the radar as a function of time. The range-time-intensity (RTI) plots obtained through power spectrum analysis reveal the quasi-periodic striations, which are known as LQP (Low-altitude QP) echoes. Our interferometer analysis allows one to investigate the motion (i.e. "tracking") of the LQP echo patches in three dimensions. This method is superior to just evaluating the variations of the echo power as a function of range and time in the standard RTI-plots. By applying this method, we show that the echo patches in different striations remain at almost the same altitude when we trace the isolated echoing regions until they disappear from the radar view. We further compare the rate of change of the range (range rate dR/dt) by two techniques: one by simply measuring the varying slope of the LQP echoes from RTI plot, the other by tracking the threedimensional locations of the LQP scatterers by using the interferometer technique. We finally prove that the changes in range as a function of time, deduced from the interferometer technique, are significantly correlated with those of the standard range rate analysis. However, the standard range rate analysis does not provide information about the correct location and the variation of the LQP irregularities. The threedimensional analysis, which we introduced for tracking individual striations, shows that LQP echo patches are confined to between 98 and 100 km altitude. This suggests that the irregularities which cause the LQP echoes drifted through the radar beam at approximately constant altitude, which we tend to attribute to a region of large-scale vertical shear of the horizontal wind.

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Section: Introductionmentioning

confidence: 64%

Three-dimensional tracking of mid-latitude quasi-periodic E-region echoes observed with the Chung-Li VHF radar

Chen

Röttger

et al. 2005

Ann. Geophys.

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“…[22] There are a number of observed phenomena that exhibit the same peculiar alignment preferred by the instability: frontal structures in E s layers, implied by time delay measurements of LORAN transmissions [Sinno et al, 1964], by ionosonde soundings [Goodwin and Summers, 1970], and by scintilations [Bowman, 1989]; frontal structures in quasi-periodic echoes, implied by radar [Yamamoto et al, 1998] and rocket [Tsunoda et al, 2000] observations; and frontal structures in the F region, implied by comparison of radar and all sky camera observations, and explained so far by invoking the Perkins instability [e.g., Kelley and Makela, 2001]. The latter observation is relevant in light of the work in Tsunoda and Cosgrove [2001], where a possible coupling between the Perkins instability and an E s layer instability is described.…”

Section: Discussionmentioning

confidence: 99%

A direction‐dependent instability of sporadic‐E layers in the nighttime midlatitude ionosphere

Cosgrove

Tsunoda

2002

Geophysical Research Letters

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144

214

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[1] The configuration of a midlatitude sporadic-E (E s ) layer at a zonal wind-shear node has been assumed to be a stable equilibrium, as long as the wind shear is hydrodynamically stable. In this paper, we show that this equilibrium is in fact unstable, at night, to electrodynamical forces that arise when plane wave perturbations in altitude or density are imposed on the E s layer. We show that the growth rate of the instability depends on the azimuthal alignment of the phase fronts of the plane-wave distortion, a feature that is reminiscient of the Perkins instability [Perkins, 1973]. The dependence on azimuth is consistent with observations of structure in E s layers that show the same preferred alignment.INDEX TERMS: 2471 Ionosphere: Plasma waves and instabilities. Citation: Cosgrove, R. B., and R. T. Tsunoda, A direction-dependent instability of sporadic-E layers in the nighttime midlatitude ionosphere, Geophys. Res.

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“…Sounding rocket campaigns from Japan (SEEK) and Puerto Rico (El Co-qui) failed to uncover evidence either of gravity waves in the mesosphere/ lower thermosphere region propagating in the direction of the QP echoes or of tilted and deformed sporadic E layers [Fukao et al, 1998; RosarioRoman et al, 1999]. Instead, gravity waves in the mesosphere were observed propagating in the direction opposite the QP echoes, neutral winds in the lower thermosphere were shown to be dominated by intense jets with strong shears, and the E region plasma density was found to remain horizontally stratified [Nakamura et al, 1998;Larsen et al, 1998;Yamamoto et al, 1998]. Recently, Tsunoda et al [1999] presented evidence of a high multiplicity of QP echoes, with up to eight echoes being visible to the radar at one time.…”

Section: Introductionmentioning

confidence: 99%

The 30‐MHz radar interferometer studies of midlatitude E region irregularities

Hysell¹,

Burcham²

2000

J. Geophys. Res.

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Structures in sporadic‐E observed with an impedance probe during the SEEK Campaign: Comparisons with neutral‐wind and radar‐echo observations

Cited by 42 publications

References 7 publications

Three-dimensional tracking of mid-latitude quasi-periodic E-region echoes observed with the Chung-Li VHF radar

Three-dimensional tracking of mid-latitude quasi-periodic E-region echoes observed with the Chung-Li VHF radar

A direction‐dependent instability of sporadic‐E layers in the nighttime midlatitude ionosphere

The 30‐MHz radar interferometer studies of midlatitude E region irregularities

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