Statistical characteristics of low-latitude ionospheric field-aligned irregularities obtained with the Piura VHF radar

Chau, Jorge L.; Woodman, R. F.; Flores, Luis

doi:10.5194/angeo-20-1203-2002

Cited by 39 publications

(86 citation statements)

References 33 publications

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“…Observations on E region FAIs from Kototabang, however, have been limited so far. Echo occurrence and spectral characteristics revealed from these observations have been found to be close to those observed in mid-latitudes and distinctly different from those of equatorial electrojet (for details, see Chau et al, 2002;Patra et al, 2004). It may be noted that these radars are located in the 6-11 • magnetic latitude belt.…”

Section: Introductionmentioning

confidence: 81%

“…It may be noted that these radars are located in the 6-11 • magnetic latitude belt. Chau et al (2002) have made a detailed investigation on the diurnal and seasonal variations of low-latitude E region FAIs based on Piura radar observations. Patra et al (2004) made a detailed study on the diurnal variation of echo occurrence and spectral parameters based on Gadanki observations and compared it in detail with those reported by Chau et al (2002).…”

Section: Introductionmentioning

confidence: 99%

“…Chau et al (2002) have made a detailed investigation on the diurnal and seasonal variations of low-latitude E region FAIs based on Piura radar observations. Patra et al (2004) made a detailed study on the diurnal variation of echo occurrence and spectral parameters based on Gadanki observations and compared it in detail with those reported by Chau et al (2002). These reports showed that during noontime, while the echoes disappear at Piura, they occur quite frequently at Gadanki (Chau et al, 2002;Patra et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

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Seasonal variation of low-latitude E-region plasma irregularities studied using Gadanki radar and ionosonde

et al. 2008

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Abstract. In this paper, we present seasonal variation of E region field-aligned irregularities (FAIs) observed using the Gadanki radar and compare them with the seasonal variation of E s observed from a nearby location SHAR. During daytime, FAIs occur maximum in summer and throughout the day, as compared to other seasons. During nighttime, FAIs occur equally in both summer and winter, and relatively less in equinoxes. Seasonal variations of E s (i.e. f t E s and f b E s ) show that the daytime activity is maximum in summer and the nighttime activity is maximum in equinoxes. No relation is found between FAIs occurrence/SNR and f t E s /f b E s . FAIs occurrence, however, is found to be related well with (f t E s −f b E s ). This aspect is discussed in the light of the present understanding of the mid-latitude E s -FAIs relationship. The seasonal variations of FAIs observed at Gadanki are compared in detail with those of Piura, which show a significant difference in the daytime observations. The observed difference has been discussed considering the factors governing the generation of FAIs.

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Section: Introductionmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Seasonal variation of low-latitude E-region plasma irregularities studied using Gadanki radar and ionosonde

et al. 2008

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“…As suggested by Tsunoda and Ecklund (2004) the lack of seasonal variability over Jicamarca might be due to weaker sporadic E s activities observed in Jicamarca's longitude sector. However, Chau et al (2002) have shown that VHF radar echoes associated with E s layers in the Jicamarca sector -observed with the Piura radar (∼900 km north of Jicamarca) -are stronger and more frequent during the southern summer, i.e. December solstice.…”

Section: Discussionmentioning

confidence: 99%

Statistics of 150-km echoes over Jicamarca based on low-power VHF observations

Chau

Kudeki

2006

Ann. Geophys.

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Abstract. In this work we summarize the statistics of the socalled 150-km echoes obtained with a low-power VHF radar operation at the Jicamarca Radio Observatory (11.97 • S, 76.87 • W, and 1.3 • dip angle at 150-km altitude) in Peru. Our results are based on almost four years of observations between August 2001 and July 2005 (approximately 150 days per year). The majority of the observations have been conducted between 08:00 and 17:00 LT. We present the statistics of occurrence of the echoes for each of the four seasons as a function of time of day and altitude. The occurrence frequency of the echoes is ∼75% around noon and start decreasing after 15:00 LT and disappear after 17:00 LT in all seasons. As shown in previous campaign observations, the 150-echoes appear at a higher altitude (>150 km) in narrow layers in the morning, reaching lower altitudes (∼135 km) around noon, and disappear at higher altitudes (>150 km) after 17:00 LT. We show that although 150-km echoes are observed all year long, they exhibit a clear seasonal variability on altitudinal coverage and the percentage of occurrence around noon and early in the morning. We also show that there is a strong day-to-day variability, and no correlation with magnetic activity. Although our results do not solve the 150-km riddle, they should be taken into account when a reasonable theory is proposed.

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“…There is still an open question on the reverse effect: how do the E-region irregularities at the foot of the flux tubes observed at the equator affect the formation of Spread F irregularities there? A correlation study was performed using the Piura VHF radar and Jicamarca simultaneously (Chau et al, 2002). Piura observed E-and F-region irregularities and Jicamarca the latter.…”

Section: Satellites Rockets and Other Radars And Radar Techniquesmentioning

confidence: 99%

Spread F – an old equatorial aeronomy problem finally resolved?

2009

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Abstract. One of the oldest scientific topics in EquatorialAeronomy is related to Spread-F. It includes all our efforts to understand the physical mechanisms responsible for the existence of ionospheric F-region irregularities, the spread of the traces in a night-time equatorial ionogram -hence its name -and all other manifestations of the same. It was observed for the first time as an abnormal ionogram in Huancayo, about 70 years ago. But only recently are we coming to understand the physical mechanisms responsible for its occurrence and its capricious day to day variability. Several additional techniques have been used to reveal the spatial and temporal characteristics of the F-region irregularities responsible for the phenomenon. Among them we have, in chronological order, radio star scintillations, trans-equatorial radio propagation, satellite scintillations, radar backscatter, satellite and rocket in situ measurements, airglow, total electron content techniques using the propagation of satellite radio signals and, recently, radar imaging techniques. Theoretical efforts are as old as the observations. Nevertheless, 32 years after their discovery, Jicamarca radar observations showed that none of the theories that had been put forward could explain them completely. The observations showed that irregularities were detected at altitudes that were stable according to the mechanisms proposed. A breakthrough came a few years later, again from Jicamarca, by showing that some of the "stable" regions had become unstable by the non-linear propagation of the irregularities from the unstable to the stable region of the ionosphere in the form of bubbles of low density plasma. A problem remained, however; the primary instability mechanism proposed, an extended (generalized) Rayleigh-Taylor instability, was too slow to explain the rapid development seen by the observations. Gravity waves in the neutral background have been proposed as a seeding mechaCorrespondence to: R. F. Woodman (ronw@geo.igp.gob.pe) nism to form irregularities from which the instability would grow, but the former are difficult to observe as a controlling parameter. Their actual role still needs to be determined. More recently, radar observations again have shown the existence of horizontal plasma drift velocities counter streaming the neutral wind at the steep bottom of the F-region which produces a fast growing instability from which a generalized Rayleigh-Taylor instability can grow. The mechanisms proposed would explain the rapid development of the large and medium scale irregularities that have been observed, including some seen only by radars. Nevertheless, a proper quantitative theoretical mechanism that would explain how these irregularities break into the very important meter scale ones, responsible for the radar echoes, needs to be developed. This paper makes a selective historical review of the observations and proposed theories since the phenomenon was discovered to our current understanding.

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Statistical characteristics of low-latitude ionospheric field-aligned irregularities obtained with the Piura VHF radar

Cited by 39 publications

References 33 publications

Seasonal variation of low-latitude E-region plasma irregularities studied using Gadanki radar and ionosonde

Seasonal variation of low-latitude E-region plasma irregularities studied using Gadanki radar and ionosonde

Statistics of 150-km echoes over Jicamarca based on low-power VHF observations

Spread F – an old equatorial aeronomy problem finally resolved?

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