Characteristics of 150 km echoes linked with solar eclipse and their implications to the echoing phenomenon

Patra, Amit; Chaitanya, P. Pavan; Tiwari, Diwakar

doi:10.1029/2010ja016258

Cited by 16 publications

(23 citation statements)

References 26 publications

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“…On the other hand, the lower echoing layer displays the necklace pattern that is similar to the solar zenith angle dependence of the F 1 layer height [ Kudeki and Fawcett , 1993]. Very recently, Patra et al [2011] have shown that such 150 km echoing pattern is closely related to the time evolution of F 1 layer density gradient. Thus the lower echoing layer can be attributed to the conventional 150 km echoes linked with the solar zenith angle dependence of the F 1 layer density gradients.…”

Section: Discussionmentioning

confidence: 97%

“… Tsunoda and Ecklund [2008] also invoked the involvement of metallic ions in the formation and transport of small plasma density structures. Patra et al [2011] have further argued that the daytime 150 km echoes and the nighttime echoes from the same height region displaying descending properties but with different vigor [ Patra and Rao , 2007b] are possibly of the same instability origin.…”

Section: Discussionmentioning

confidence: 99%

“…Interchange instability of some kind is believed to be responsible for the generation of the 150 km irregularities [ Kudeki and Fawcett , 1993; Tsunoda and Ecklund , 2000]. Recently, Patra et al [2011], using observations made during a solar eclipse, have provided experimental evidence on the role of the density gradient associated with the F 1 layer in the echoing process. They advocated for the interchange instability proposed earlier by Kudeki and Fawcett [1993] and underlined the combined role of density gradient and recombination rate in the growth of the instability.…”

Section: Introductionmentioning

confidence: 99%

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Descending ion layer property in the Gadanki radar observations of 150 km echoes and its implication to the echoing phenomenon

Patra

2011

J. Geophys. Res.

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Gadanki radar observations of the daytime 150 km echoes displaying descending features, resembling the descending ion layer behavior, are presented. The descending pattern is intriguing since it indicates the possible role of density gradient associated with the ion layer in generating the irregularities responsible for 150 km radar echoes, not envisioned before. Unusually strong SNR and narrow spectral features of these echoes clearly indicate the role of sharp density gradients in the echoing process. Given the fact that Gadanki is located at magnetically low latitude, it is argued that these descending echoing layers are produced by interchange instability on the gradient of daytime descending ion layer formed by meridional wind shear associated with tidal/gravity waves quite similar to that observed during nighttime. The observations reported here are first of its kind illustrating the role of density gradient layers and are important in furthering our understanding on the puzzling 150 km echoing phenomenon.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Descending ion layer property in the Gadanki radar observations of 150 km echoes and its implication to the echoing phenomenon

Patra

2011

J. Geophys. Res.

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“…It explains the necklace shape because EUV photons penetrate most deeply at noon and less so at other times of the day as the photons have to travel through more atmosphere before encountering the same depth. It also explains why the echoes disappeared during the partial solar eclipse observed over the Gadanki radar site [ Patra et al , ] and why they were enhanced during a solar flare [ Reyes , ]. It may explain why they show the vertical structuring seen in Figure by invoking resonances which optimize this process at some altitudes and not others.…”

Section: Introductionmentioning

confidence: 99%

Photoelectron‐induced waves: A likely source of 150 km radar echoes and enhanced electron modes

Oppenheim

Dimant

2016

Geophysical Research Letters

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VHF radars near the geomagnetic equator receive coherent reflections from plasma density irregularities between 130 and 160 km in altitude during the daytime. Though researchers first discovered these 150 km echoes over 50 years ago and use them to monitor vertical plasma drifts, the underlying mechanism that creates them remains a mystery. This paper uses large‐scale kinetic simulations to show that photoelectrons can drive electron waves, which then enhance ion density irregularities that radars could observe as 150 km echoes. This model explains why 150 km echoes exist only during the day and why they appear at their lowest altitudes near noon. It predicts the spectral structure observed by Chau (2004) and suggests observations that can further evaluate this mechanism. It also shows the types and strength of electron modes that photoelectron‐wave interactions generate in a magnetized plasma.

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“…Since the early observations made by the Jicamarca ISR in the 1960s, coherent scatter echoes have been observed from regions around 150 km altitude during daytime (Balsley, 1964). The origin of these echoes is still not understood since there are no obvious sources for plasma instabilities and, therefore, plasma irregularities in that region (Tsunoda and Ecklund, 2000;Patra et al, 2011).…”

Section: F S Rodrigues Et Al: Equatorial Vertical Drifts In Brazilmentioning

confidence: 99%

Equatorial 150 km echoes and daytime F region vertical plasma drifts in the Brazilian longitude sector

et al. 2013

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Abstract. Previous studies showed that conventional coherent backscatter radar measurements of the Doppler velocity of the so-called 150 km echoes can provide an alternative way of estimating ionospheric vertical plasma drifts during daytime hours (Kudeki and Fawcett, 1993;Chau and Woodman, 2004). Using observations made by a small, lowpower 30 MHz coherent backscatter radar located in the equatorial site of São Luís (2.59 • S, 44.21 • W; −2.35 • dip lat), we were able to detect and monitor the occurrence of 150 km echoes in the Brazilian sector. Using these measurements we estimated the local time variation of daytime vertical ionospheric drifts in the eastern American sector. Here, we present a few interesting cases of 150 km-echoes observations made by the São Luís radar and estimates of the diurnal variation of vertical drifts. These cases exemplify the variability of the vertical drifts in the Brazilian sector. Using same-day 150 km-echoes measurements made at the Jicamarca Radio Observatory in Peru, we also demonstrate the variability of the equatorial vertical drifts across the American sector. In addition to first estimates of the absolute vertical plasma drifts in the eastern American (Brazilian) sector, we also present observations of abnormal drifts detected by the São Luís radar associated with the 2009 major sudden stratospheric warming event.

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Characteristics of 150 km echoes linked with solar eclipse and their implications to the echoing phenomenon

Cited by 16 publications

References 26 publications

Descending ion layer property in the Gadanki radar observations of 150 km echoes and its implication to the echoing phenomenon

Descending ion layer property in the Gadanki radar observations of 150 km echoes and its implication to the echoing phenomenon

Photoelectron‐induced waves: A likely source of 150 km radar echoes and enhanced electron modes

Equatorial 150 km echoes and daytime F region vertical plasma drifts in the Brazilian longitude sector

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