Low‐latitude field‐aligned irregularities observed in the <i>E</i> region with the Piura VHF radar: First results

Woodman, R. F.; Chau, Jorge L.; Aquino, Fredy; Rodriguez, Rodolfo R.; Flores, Luis

doi:10.1029/1999rs900027

Cited by 31 publications

(28 citation statements)

References 15 publications

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“…In general, we have been able to corroborate most of the characteristics of the E-region irregularities already published by Woodman et al (1999) using only a few days of data, namely that the Piura E-region echoes (1) occur mainly at night, (2) are generated by the gradient drift instability, and (3) could be classified into lower and upper region echoes. Based on 18 months of continuous observations, the seasonal and diurnal occurrences, as well as Doppler velocities, have also been presented and discussed.…”

Section: Discussionsupporting

confidence: 73%

“…The main features of E-region irregularities obtained from these intermittent campaigns have already been presented by Woodman et al (1999) and Chau and Woodman (1999). Here we present just one example and summarize the results previously obtained in order to avoid duplication.…”

Section: Intermittent E-region Observationsmentioning

confidence: 67%

“…1, we show altitude-time signal-to-noise ratio (SNR) values obtained from E-region irregularities observed on 31 October 1998. In this particular example we are able to clearly distinguish between the two regions described by Woodman et al (1999), namely the lower, continuous-type E-region echoes (95 − 105 km) and the upper, patchy-type E-region echoes (105 − 120 km). As it can be seen, the latter echoes, when observed with high time resolution, show quasi-periodic characteristics like those reported at mid-latitudes.…”

Section: Intermittent E-region Observationsmentioning

confidence: 75%

“…In this paper, we extend the results presented by Woodman et al (1999) based on 15 days of data, by making use of more data taken intermittently between 1991 and 1999. Particular emphasis is given to the concurrent observations of FAIs between the Piura and the Jicamarca radars.…”

Section: Introductionmentioning

confidence: 98%

“…Between 1991 and 1999, we have sporadically interrupted its normal observations to study the characteristics of E-region and F-region irregularities. Preliminary results have been published by Woodman et al (1999) and Chau and Woodman (1999). Although the Piura observations are taken at a similar magnetic latitude as the Gandaki radar in India, they are very unique, since Piura is located in the southern geographic hemisphere.…”

Section: Introductionmentioning

confidence: 99%

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

Chau

Woodman²,

Flores³

2002

Ann. Geophys.

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Abstract. We present a summary of the statistical characteristics of echoes from ionospheric (E-and F-region) fieldaligned irregularities obtained with the Piura VHF radar. This radar is located at ∼7.0 • dip latitude, just outside the equatorial electrojet (EEJ) region. Our results are based on (1) intermittent observations made between 1991 and 1999 just few days a year, and (2) continuous observations made between January 2000 and June 2001. During most of the intermittent observations, simultaneous measurements of EEJ and equatorial spread F (ESF) irregularities were performed with the Jicamarca VHF radar. From the continuous measurements, we have obtained the diurnal and seasonal characteristics of a variety of parameters (percentage of occurrence, signal-to-noise ratio and/or Doppler velocities) from the lower and upper E-region irregularities and also from F-region irregularities over Piura. For example, we have found that (1) the E-region echoes are stronger and occur more frequently during local summer (i.e. between December and March); (2) between May and June, the E-region echoes are weaker and occur less frequently; moreover, during these months, a semidiurnal wave with large amplitudes is observed in the meridional wind (> 100 m s −1 ); (3) there is vertical wavelength of about 20 km in the Doppler velocity, particularly after midnight; (4) the lower (upper) Eregion Doppler velocities are influenced mainly by meridional winds (equatorial F-region vertical drifts). In addition, we have observed that the seasonal and daily occurrences of Piura F-region irregularities are similar to the occurrence of topside ESF irregularities over Jicamarca. The likelihood of occurrence of F-region irregularities over Piura and, therefore, topside ESF over Jicamarca is greater when there are no E-region irregularities over Piura. On the other hand, there is more probability of observing bottomtype/bottomside ESF irregularities over Jicamarca when E-region irregularities are observed over Piura.

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Section: Discussionsupporting

confidence: 73%

Section: Intermittent E-region Observationsmentioning

confidence: 67%

Section: Intermittent E-region Observationsmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Chau

Woodman²,

Flores³

2002

Ann. Geophys.

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First results on low‐latitude E and F region irregularities obtained using the Gadanki Ionospheric Radar Interferometer

et al. 2014

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A 30 MHz radar has recently been established at Gadanki (13.5°N, 79.2°E; 6.5°N magnetic latitude) to make unattended observations of the ionospheric field-aligned irregularities (FAI). This radar, called the Gadanki Ionospheric Radar Interferometer (GIRI), has been designed to have scanning capability of 100°in the east-west plane perpendicular to Earth's magnetic field and interferometry/imaging system to study drifts and spatial distribution of plasma irregularities at both large and small scales. In this paper, we present the first results on the E and F region FAI made using the scanning capability of the GIRI. Daytime observations of E region FAI show type 2 echoes with velocities predominantly upward northward (downward-southward) at altitudes >100 km (<100 km) and westward (eastward) in the forenoon (afternoon) with signature of tidal wind field. F region irregularities show bottom-type, bottomside and plume structures with close resemblance to those observed over the magnetic equator. Observations made with the east-west scanning capability have been used to study the origin, evolution, and drift of the FAI for the first time from Gadanki. Eastward drifts are estimated to be 90-210 m s À1 during 20-24 LT. Upward velocity as large as 500 m s À1 has been observed in the initial phase of the plume structures. Intriguingly, downward velocity as large as 60 m s À1 has also been observed in the plumes, displaying descending pattern, observed in the early evening hours. These results are presented and discussed in the light of current understanding of low-latitude plasma irregularities, and future prospects of GIRI are outlined.

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Low latitude E-region irregularities studied using Gadanki radar, ionosonde and in situ measured electron density

Kumar

Patra

Kwak

et al. 2009

Astrophys Space Sci

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In this paper, we attempt to identify the driving forces responsible for the generation of low-latitude Eregion field-aligned irregularities (FAIs). It is evident that the low-latitude E-region FAIs occur both during the day and night with preferential occurrence being most during local sunrise period. Simultaneous measurements are made with Gadanki radar and nearby located Ionosonde for understanding the low-latitude Es-FAIs relationship. The observations suggest that the occurrence and SNR of FAIs have a close relationship with f t E s -f b E s . Finally, using the past electron density profiles and reasonable values of electric field, we have shown that it is generally difficult with the gradient drift instability to explain low-latitude E-region FAIs when electric field alone is considered as driving agency. We hypothesize that neutral winds play important role for the generation of irregularities at low latitudes outside the electrojet

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Low‐latitude field‐aligned irregularities observed in the E region with the Piura VHF radar: First results

Cited by 31 publications

References 15 publications

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

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

First results on low‐latitude E and F region irregularities obtained using the Gadanki Ionospheric Radar Interferometer

Low latitude E-region irregularities studied using Gadanki radar, ionosonde and in situ measured electron density

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