A new analysis technique for estimating zonal irregularity drifts and variability in the equatorial F region using spaced receiver scintillation data

Vacchione, Joseph D.; Franke, Steven; Yeh, K. C.

doi:10.1029/rs022i005p00745

Cited by 37 publications

(35 citation statements)

References 11 publications

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“…Kil et al (2000) have shown that t 0 is variable owing to the decorrelation on the crosscorrelation function by the random velocity. The random velocities are relatively large during the generation and growth phase but they decrease with time (Vacchione et al 1987;Spatz et al 1988). Kil et al (2000) have also shown that the measured velocity is greater than the true velocity by @10 m/s before 2200 LT and by less than 1 m/s at midnight.…”

Section: Observations and Resultsmentioning

confidence: 96%

“…The scatter of the velocities could be caused by the random fluctuations of the plasma irregularities (Spatz et al 1988). Previous observations showed that the random fluctuations were large during the generation phase of the plasma bubbles (just after sunset) and that they rapidly decreased with time (Vacchione et al 1987;Spatz et al 1988). Figure 5 shows the seasonal average for the eastward drift velocities observed with the GPS receivers at Kototabang.…”

Section: Observations and Resultsmentioning

confidence: 99%

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Equatorial Ionospheric Scintillations and Zonal Irregularity Drifts Observed with Closely-Spaced GPS Receivers in Indonesia

Otsuka

Shiokawa

Ogawa

2006

Journal of the Meteorological Society of Japan

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To investigate drift velocities of a few hundred meter-scale irregularities associated with equatorial plasma bubbles, we used three single-frequency GPS receivers at the Equatorial Atmosphere Radar (EAR) site at Kototabang, Indonesia (0.20 S, 100.32 E; geomagnetic latitude 10.6 S), since January 2003. The GPS receivers sampled GPS signal intensity at a rate of 20 Hz. Distances between the receivers were 116, 127, and 152 m. An analysis of scintillation index ðS 4 Þ in two years (2003)(2004) revealed that the scintillations often occurred between 2000-0100 LT at equinoxes and that their occurrence rate was higher during March-April than during September-October. Drift velocities of irregularities were measured using cross-correlation analysis with the time series of the GPS signal intensity obtained from the three receivers. From a statistical analysis of the drift velocities, the eastward component of drift velocity just after sunset is found to be greater during March-April than during September-October. Based on these results, for the first time, we suggest that the east-west component of plasma drift velocity (or vertical electric field) may be related to the evolution of plasma irregularities causing scintillations throughout the mechanism causing the prereversal enhancement of the eastward electric fields. The equinoctial asymmetry of the drift velocity could be attributed to the equinoctial asymmetry of neutral winds in the thermosphere.

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Section: Observations and Resultsmentioning

confidence: 96%

Section: Observations and Resultsmentioning

confidence: 99%

Equatorial Ionospheric Scintillations and Zonal Irregularity Drifts Observed with Closely-Spaced GPS Receivers in Indonesia

Otsuka

Shiokawa

Ogawa

2006

Journal of the Meteorological Society of Japan

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“…Estimation of V 0 and V C from spaced receiver data does not require a knowledge of the exact form of the function f (Vacchione et al, 1987;Spatz et al, 1988;Bhattacharyya et al, 1989). However, in order to obtain information about spatial scales present in the ground scintillation pattern, it is necessary to know the form of f , such that the coherence scale d I , defined by…”

Section: Discussionmentioning

confidence: 99%

Solar flux dependence of coherence scales in scintillation patterns produced by ESF irregularities

et al. 2005

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Abstract. The coherence scale length, defined as the 50% decorrelation scale length along the magnetic east-west direction, in the ground scintillation pattern obtained at a dip equatorial location, due to scattering of VHF radio waves by equatorial spread F (ESF) irregularities, is calculated, using amplitude scintillation data recorded by two spaced receivers. The average east-west drift of the ground scintillation pattern, during the pre-and post-midnight periods, also calculated from the same observations, shows an almost linear increase with 10.7-cm solar flux. In the present paper the variability of the drift is automatically taken into account in the calculation of the coherence scale length of the ground scintillation pattern. For weak scintillations, the coherence scale depends on the Fresnel scale, which varies with the height of the irregularity layer, and also on the spectral index of the irregularity power spectrum. It is found that for weak scintillations, the coherence scales are much better organized according to the 10.7-cm solar flux, during the pre-midnight period, than during the post-midnight period, with a general trend of coherence scale length increasing with 10.7-cm solar flux except for cases with F 10.7-cm solar flux <100. This indicates that, during the initial phase of ESF irregularity development, the irregularity spectrum does not have much variability while further evolution of the spatial structure in ESF irregularities is controlled by factors other than the solar flux.

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“…Drift velocities at Ancon are calculated on-line using methods from Vacchione et al (1987). This method uses quadratic approximations near the peaks of the cross-and autocorrelation functions to estimate both the drift velocity, V 0 , and the random velocity, V c , which is related to the amount of decorrelation over the sample time interval.…”

Section: Methodsmentioning

confidence: 99%

Equatorial ionospheric zonal drift model and vertical drift statistics from UHF scintillation measurements in South America

Sheehan

Valladares

2004

Ann. Geophys.

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Abstract. UHF scintillation measurements of zonal ionospheric drifts have been conducted at Ancon, Peru since 1994 using antennas spaced in the magnetic east-west direction to cross-correlate geo-synchronous satellite signals. An empirical model of average drift over a wide range of K p and solar flux conditions was constructed from successive twodimensional fits of drift vs. the parameters and day of year. The model exhibits the typical local time trend of maximum eastward velocity in the early evening with a gradual decrease and reversal in the early morning hours. As expected, velocities at all hours increase with the solar flux and decrease with K p activity. It was also found that vertical drifts could contribute to the variability of drift measurements to the east of Ancon at a low elevation angle. The vertical drift at the ionospheric intersection to the east can be estimated when combined with nearly overhead observations at Ancon or a similar spaced-antenna site at Antofagasta, Chile. Comparisons on five days with nearly simultaneous measurements of vertical drift by the Julia radar at Jicamarca, Peru show varying agreement with the spaced-antenna estimates. Statistical results from 1997 to 2001 generally agree with radar and satellite studies.

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A new analysis technique for estimating zonal irregularity drifts and variability in the equatorial F region using spaced receiver scintillation data

Cited by 37 publications

References 11 publications

Equatorial Ionospheric Scintillations and Zonal Irregularity Drifts Observed with Closely-Spaced GPS Receivers in Indonesia

Equatorial Ionospheric Scintillations and Zonal Irregularity Drifts Observed with Closely-Spaced GPS Receivers in Indonesia

Solar flux dependence of coherence scales in scintillation patterns produced by ESF irregularities

Equatorial ionospheric zonal drift model and vertical drift statistics from UHF scintillation measurements in South America

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