Up-down asymmetry of type I plasma waves in the equatorial electrojet region

Ravindran, Sudha; Murthy, B. V. Krishna

doi:10.1007/s00585-997-0774-y

Cited by 6 publications

(3 citation statements)

References 12 publications

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“…[28] A related aspect of spectral asymmetry is an asymmetry in the phase velocity of type I waves, not just their power. It has been noted before that the phase velocity of downshifted type I waves in west beams is larger than the phase velocity of upshifted type I waves seen at the same magnetic zenith angle in east beams [Kudeki et al, 1982;Ravindran and Murthy, 1997]. However, somewhat similar to the evolution in the power asymmetry, we have also uncovered an evolution in this Doppler shift difference in our data set.…”

Section: East-west and Up-down Asymmetries In The Doppler Shiftsupporting

confidence: 86%

East‐west and vertical spectral asymmetry associated with equatorial type I waves during strong electrojet conditions: 1. Pohnpei radar observations

et al. 2006

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[1] We have studied a particularly strong vertical type I event with the equatorial Pohnpei radar. During that event, which lasted several hours, we routinely obtained type I waves in radar beams pointed vertically as well as at 14.3 degrees east and west of vertical. This data set has allowed us to revisit the question of the equatorial electrojet east-west and up-down asymmetries. These asymmetries are known to favor downshifted waves during the daytime electrojet. In our study we have contrasted type I spectra obtained simultaneously in the east and west beams, in addition to analyzing upshifted and downshifted waves in the vertical beam data. We have found that when the echoes become particularly strong, both the east-west and up-down power asymmetries may not only vanish but can even reverse their signs. Furthermore, these tendencies occur simultaneously in the east-west and up-down asymmetries. Finally, we have noted that the power asymmetry is accompanied by an asymmetry in type I Doppler shifts, which is only clearly visible, however, when the overall echo power is weaker.

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Section: East-west and Up-down Asymmetries In The Doppler Shiftsupporting

confidence: 86%

East‐west and vertical spectral asymmetry associated with equatorial type I waves during strong electrojet conditions: 1. Pohnpei radar observations

et al. 2006

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“…Generally, red-shifted spectral lines are stronger than blue-shifted lines in these daytime observation. This phenomenon is well known and has been termed the "up-down" asymmetry (Fejer et al, 1976;Farley et al, 1978;Kudeki et al, 1985;Ravindran and KrishnaMurthy, 1997). Likewise, stronger echoes are observed along westward zenith than eastward zeniths.…”

Section: Amisr Prototypementioning

confidence: 91%

Combined radar observations of equatorial electrojet irregularities at Jicamarca

et al. 2007

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Abstract. Daytime equatorial electrojet plasma irregularities were investigated using five distinct radar diagnostics at Jicamarca including range-time-intensity (RTI) mapping, Faraday rotation, radar imaging, oblique scattering, and multiplefrequency scattering using the new AMISR prototype UHF radar. Data suggest the existence of plasma density striations separated by 3-5 km and propagating slowly downward. The striations may be caused by neutral atmospheric turbulence, and a possible scenario for their formation is discussed. The Doppler shifts of type 1 echoes observed at VHF and UHF frequencies are compared and interpreted in light of a model of Farley Buneman waves based on kinetic ions and fluid electrons with thermal effects included. Finally, the up-down and east-west asymmetries evident in the radar observations are described and quantified.

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“…Since reports on the asymmetry came mainly with Jicamarca radar observations, it was proposed that this could be a result of the presence of Pacific Ocean to the west and Andes mountain to the east of the radar site [Balsley, 1970;Ierkic et al, 1980;Farley, 1985]. However, now that similar asymmetries have been clearly observed in Brazil using CUPRI [Swartz, 1997] and RESCO [Denardini et al, 2005], as well as in India [Ravindran and Murthy, 1997] and, finally, also in Pohnpei, Micronesia (paper 1), the geographical factor must clearly be discounted.…”

Section: A Review Of Proposed Asymmetry Mechanisms 221 Altitude Anmentioning

confidence: 97%

East‐west and vertical spectral asymmetry associated with equatorial type I waves during strong electrojet conditions: 2. Theory

St.-Maurice¹,

Choudhary²

2006

J. Geophys. Res.

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[1] In order to explain vertical and east-west type I asymmetries uncovered in a companion paper and in references therein, we introduce the notion that the generating large-scale gradient drift waves break down first in elongated isolated enhancement and depletion regions (blobs and holes) that follow an asymmetric nonlinear evolution. The nonlinear evolution is accompanied by a rotation of the electric field inside the structures, be they blobs or holes. It is shown here that holes have a tendency to rotate more than blobs but that as a result the electric field inside holes is also weaker. These two features (contrasting rotations and contrasting field strengths) explain the predominant sign of the up-down and east-west asymmetries during weakly to moderately driven conditions. They also explain how the asymmetry is observed to disappear and even to reverse its sign under more strongly driven conditions. Citation: St.-Maurice, J.-P., and R. K. Choudhary (2006), East-west and vertical spectral asymmetry associated with equatorial type I waves during strong electrojet conditions: 2. Theory,

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Up-down asymmetry of type I plasma waves in the equatorial electrojet region

Cited by 6 publications

References 12 publications

East‐west and vertical spectral asymmetry associated with equatorial type I waves during strong electrojet conditions: 1. Pohnpei radar observations

East‐west and vertical spectral asymmetry associated with equatorial type I waves during strong electrojet conditions: 1. Pohnpei radar observations

Combined radar observations of equatorial electrojet irregularities at Jicamarca

East‐west and vertical spectral asymmetry associated with equatorial type I waves during strong electrojet conditions: 2. Theory

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