Radar interferometric imaging of field‐aligned plasma irregularities in the equatorial electrojet

Kudeki, Erhan; Sürücü, Fahri

doi:10.1029/90gl02603

Cited by 93 publications

(60 citation statements)

References 5 publications

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“…The 50 MHz radar echoes from 3 m irregularities can also act as tracers of the large-scale irregularities traveling in the zonal and vertical direction. More recently, these large-scale irregularities have been studied using radar interferometry techniques with one or more east-west base lines (Kudeki et al, 1982(Kudeki et al, , 1985(Kudeki et al, , 1987Kudeki and Sürücü, 1991).…”

Section: Introductionmentioning

confidence: 99%

Solar cycle dependent characteristics of the equatorial blanketing Es layers and associated irregularities

2006

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Abstract. The occurrence of blanketing type E s (E sb ) layers and associated E-region irregularities over the magnetic equatorial location of Trivandrum (8.5 • N; 77 • E; dip ∼0.5 • ) during the summer solstitial months of May, June, July and August has been investigated in detail for the period 1986-2000 to bring out the variabilities in their characteristics with the solar cycle changes. The study has been made using the ionosonde and magnetometer data of Trivandrum from 1986-2000 along with the available data from the 54.95 MHz VHF backscatter radar at Trivandrum for the period 1995-2000. The appearance of blanketing E s layers during these months is observed to be mostly in association with the occurrence of afternoon Counter Electrojet (CEJ) events. The physical process leading to the occurrence of a CEJ event is mainly controlled by the nature of the prevailing electro dynamical/neutral dynamical conditions before the event.Hence it is natural that the E sb layer characteristics like the frequency of occurrence, onset time, intensity, nature of gradients in its top and bottom sides etc are also affected by the nature of the background electro dynamical /neutral dynamical processes which in turn are strongly controlled by the solar activity changes. The occurrence of E sb layers during the solstitial months is found to show very strong solar activity dependence with the occurrence frequency being very large during the solar minimum years and very low during solar maximum years. The intensity of the VHF radar backscattered signals from the E sb irregularities is observed to be controlled by the relative roles of the direction and magnitude of the prevailing vertical polarization electric field and the vertical electron density gradient of the prevailing E sb layer depending on the phase of the solar cycle. The gradient of the E sb layer shows a more dominant role in the generation of gradient instabilities during solar minimum periods while it is the electric field that has a more dominant role during solar maximum periods.

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Section: Introductionmentioning

confidence: 99%

Solar cycle dependent characteristics of the equatorial blanketing Es layers and associated irregularities

2006

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“…Since the pioneering work of Kudeki and Sürücü (1991) to study the EEJ, radar imaging has been improved and extended to study other phenomena. At Jicamarca, these include equatorial spread-F (Hysell, 1999), lower atmosphere and meteors Woodman, 2001, 2004), while mid-latitude E-region irregularities are beginning to be studied using radar imaging at the Piura and MU radars.…”

Section: Interferometric Imagingmentioning

confidence: 99%

“…The first examples of ionospheric radar interferometric observations interpreted in terms of images were provided by Kudeki and Sürücü (1991), using four receiving antennas with nonredundant spacing, resulting in six baselines. For imaging of the scattering from equatorial spread-F , Hysell (1996) introduced the Maximum Entropy algorithm pioneered for applications in radio astronomy (Wilczek and Drapatz, 1985).…”

Section: Interferometric Imagingmentioning

confidence: 99%

An imaging interferometry capability for the EISCAT Svalbard Radar

Grydeland

Chau²,

Hoz

et al. 2005

Ann. Geophys.

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Abstract. Interferometric imaging (aperture synthesis imaging) is a technique used by radio astronomers to achieve angular resolution that far surpasses what is possible with a single large aperture. A similar technique has been used for radar imaging studies of equatorial ionospheric phenomena at the Jicamarca Radio Observatory. We present plans for adding an interferometric imaging capability to the EISCAT Svalbard Radar (ESR), a capability which will contribute significantly to several areas of active research, including naturally and artificially enhanced ion-acoustic echoes and their detailed relation in space and time to optical phenomena, polar mesospheric summer echoes (PMSE), and meteor studies.Interferometry using the two antennas of the ESR has demonstrated the existence of extremely narrow, fieldaligned scattering structures, but having only a single baseline is a severe limitation for such studies. Building additional IS-class antennas at the ESR is not a trivial task. However, the very high scattering levels in enhanced ion-acoustic echoes and PMSE means that a passive receiver antenna of more modest gain should still be capable of detecting these echoes.In this paper we present simulations of what an imaging interferometer will be capable of observing for different antenna configurations and brightness distributions, under ideal conditions, using two different image inversion algorithms. We also discuss different antenna and receiver technologies.

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“…Coherent backscatter radar imaging has been used for investigations of equatorial spread F. These investigations have been performed, predominantly, in the Peruvian longitude sector using measurements made by the radar and antenna modules of the Jicamarca Radio Observatory (e.g., Kudeki and Sürücü, 1991;Hysell and Woodman, 1997;Hysell and Chau, 2006;Harding and Milla, 2013) with only a couple of exceptions (Rodrigues et al, 2008(Rodrigues et al, , 2012. Initial studies used Fourier-based analyses of the measurements (Kudeki and Sürücü, 1991).…”

Section: Introductionmentioning

confidence: 99%

“…Initial studies used Fourier-based analyses of the measurements (Kudeki and Sürücü, 1991). More advanced techniques, using the maximum entropy algorithm (MaxEnt), were implemented by Hysell (1996).…”

Section: Introductionmentioning

confidence: 99%

High-resolution coherent backscatter interferometric radar images of equatorial spread F using Capon's method

2017

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Abstract. We present results of Capon's method for estimation of in-beam images of ionospheric scattering structures observed by a small, low-power coherent backscatter interferometer. The radar interferometer operated in the equatorial site of São Luís, Brazil (2.59 • S, 44.21 • W, −2.35 • dip latitude). We show numerical simulations that evaluate the performance of the Capon method for typical F region measurement conditions. Numerical simulations show that, despite the short baselines of the São Luís radar, the Capon technique is capable of distinguishing localized features with kilometric scale sizes (in the zonal direction) at F region heights. Following the simulations, we applied the Capon algorithm to actual measurements made by the São Luís interferometer during a typical equatorial spread F (ESF) event. As indicated by the simulations, the Capon method produced images that were better resolved than those produced by the Fourier method. The Capon images show narrow (a few kilometers wide) scattering channels associated with ESF plumes and scattering regions spaced by only a few tens of kilometers in the zonal direction. The images are also capable of resolving bifurcations and the C shape of scattering structures.

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Radar interferometric imaging of field‐aligned plasma irregularities in the equatorial electrojet

Cited by 93 publications

References 5 publications

Solar cycle dependent characteristics of the equatorial blanketing E<sub><i>s</i></sub> layers and associated irregularities

Solar cycle dependent characteristics of the equatorial blanketing E<sub><i>s</i></sub> layers and associated irregularities

An imaging interferometry capability for the EISCAT Svalbard Radar

High-resolution coherent backscatter interferometric radar images of equatorial spread F using Capon's method

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Radar interferometric imaging of field‐aligned plasma irregularities in the equatorial electrojet

Cited by 93 publications

References 5 publications

Solar cycle dependent characteristics of the equatorial blanketing E&lt;sub&gt;&lt;i&gt;s&lt;/i&gt;&lt;/sub&gt; layers and associated irregularities

Solar cycle dependent characteristics of the equatorial blanketing E&lt;sub&gt;&lt;i&gt;s&lt;/i&gt;&lt;/sub&gt; layers and associated irregularities

An imaging interferometry capability for the EISCAT Svalbard Radar

High-resolution coherent backscatter interferometric radar images of equatorial spread F using Capon's method

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Solar cycle dependent characteristics of the equatorial blanketing E<sub><i>s</i></sub> layers and associated irregularities

Solar cycle dependent characteristics of the equatorial blanketing E<sub><i>s</i></sub> layers and associated irregularities