First Dual‐Frequency Radar Observations of 150‐km Echoes From Gadanki and Implications

Patra, Amit; Chaitanya, P. Pavan; Rao, M. Durga; Kamaraj, P.

doi:10.1029/2017gl076749

Cited by 3 publications

(22 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Also note that the observation of larger spectral width at 30 MHz than that at 53 MHz illustrated here is opposite to that reported by Patra et al (2018). In order to gain insight on the manifestation of type-A and type-B echoes, in the following, we re-examine the observations reported earlier by Patra et al (2018). In order to gain insight on the manifestation of type-A and type-B echoes, in the following, we re-examine the observations reported earlier by Patra et al (2018).…”

Section: Comparative Analysis Of Common Observationscontrasting

confidence: 99%

“…These figures suggest that the echoes fall under the so-called type-B 150-km echoes. Also note that the observation of larger spectral width at 30 MHz than that at 53 MHz illustrated here is opposite to that reported by Patra et al (2018). Also note that the observation of larger spectral width at 30 MHz than that at 53 MHz illustrated here is opposite to that reported by Patra et al (2018).…”

Section: Comparative Analysis Of Common Observationscontrasting

confidence: 98%

“…Figure 3c shows scatterplots of SNR and spectral width observed by the two radars. Note that no type-A echo was observed in these dual-frequency experiments unlike those of Patra et al (2018). Note that no type-A echo was observed in these dual-frequency experiments unlike those of Patra et al (2018).…”

Section: Comparative Analysis Of Common Observationsmentioning

confidence: 77%

“…Note that no type-A echo was observed in these dual-frequency experiments unlike those of Patra et al (2018). It may be recalled that Patra et al (2018) used the full system of the 53-MHz MST radar, which was~18 dB higher than that used here. It may be recalled that Patra et al (2018) used the full system of the 53-MHz MST radar, which was~18 dB higher than that used here.…”

Section: Comparative Analysis Of Common Observationsmentioning

confidence: 79%

“…Here we re-examine dual-frequency radar observations reported by Patra et al (2018) and consider only those SNR and spectral width data which correspond to common height and time bins of both radar observations. It may, however, be mentioned that these observations were related to partly overlapping volume since observations made at 53 MHz were made using the full system of the MST radar (for details, refer to Patra et al, 2018).…”

Section: Reanalysis Of Previous Dual-frequency Radar Observationsmentioning

confidence: 99%

See 4 more Smart Citations

Common‐Volume Dual‐Frequency Radar Observations of 150‐km Echoes and Implications

et al. 2020

Self Cite

View full text Add to dashboard Cite

We present and discuss common-volume dual-frequency radar observations of 150-km echoes made at 30 and 53 MHz from Gadanki by employing identical transmitter power and antenna beam width. These controlled experiments reveal that 150-km echoes are stronger, broader in spectral width, and more frequent in their occurrence at 30 MHz than at 53 MHz. Echo intensities at 30 and 53 MHz are found to be consistent with the rocket-borne observations of wave number spectrum of meter-scale irregularities in the 150-km region. The frequency dependence of spectral widths of the echoes while is found to be somewhat similar to that of electrojet type-1 echoes it is opposite to that of electrojet type-2 echoes and also to that of incoherent scattering in direction perpendicular to magnetic field. Spectral widths of the echoes observed by both radars are found to be independent of SNR. A detailed comparison of these observations with those made earlier suggests that instrument functions play an important role in manifesting SNR-dependent/independent spectral width property of the 150-km echoes. The narrow spectral properties and frequency dependence of echo intensity and spectral width clearly suggest that the irregularities responsible for the radar backscatter are linked with weak plasma turbulence and the meter-scale irregularities responsible for radar echoes ought to be growing with direct injection of energy at the meter scale itself to overcome damping. We surmise the potential role of photoelectrons and atmospheric gravity waves in the underline plasma instability process.

show abstract

Section: Comparative Analysis Of Common Observationscontrasting

confidence: 99%

Section: Comparative Analysis Of Common Observationscontrasting

confidence: 98%

Section: Comparative Analysis Of Common Observationsmentioning

confidence: 77%

Section: Comparative Analysis Of Common Observationsmentioning

confidence: 79%

Section: Reanalysis Of Previous Dual-frequency Radar Observationsmentioning

confidence: 99%

See 3 more Smart Citations

Common‐Volume Dual‐Frequency Radar Observations of 150‐km Echoes and Implications

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

On the Nature of F‐Region Bottom‐Type Echoing Layer Over Gadanki

Chaitanya

Patra

2021

JGR Space Physics

Self Cite

View full text Add to dashboard Cite

Bottom‐type echoing layers observed from Gadanki are presented and analyzed. The analysis is based on observations made using a substantial database of the 30 MHz Gadanki Ionospheric Radar Interferometer (GIRI) during 2017–2019, collocated digisonde observations, and a few days of overlapping volume observations made using the GIRI and the 53 MHz Advanced Indian MST Radar (AIR) . The echoes commence well before the E‐ and F‐region sunsets and last as late as 23:00 Local Time. The echoing layers occur in the height range of 220–300 km with a thickness of 10–15 km and the Doppler spectra are narrow with spectral width confined to 10 m s−1. The echoing layers are very common during the entire observational period and do not show any noticeable seasonal dependence. The zonal velocities of the irregularities responsible for the radar echoes are close to zero irrespective of the height of the echoing region. The echoes are stronger at 30 MHz than at 53 MHz indicating strong Bragg scale dependence. The height of the echoing layer agrees very well with the height of the F‐region peak electron density (hmF2). Also, early commencement of the echoing layer is found to be associated with low hmF2 and corresponding high electron density (foF2). While the results indicate toward the wind‐driven interchange instability as their origin, the early onset of the echoing layer and its relationship with the background ionospheric parameters call for explanation. The results are discussed in the light of current understanding on the bottom‐type echoing layer.

show abstract

Solved and unsolved riddles about low-latitude daytime valley region plasma waves and 150-km echoes

Chau

Longley²,

Reyes³

et al. 2023

Front. Astron. Space Sci.

View full text Add to dashboard Cite

The Earth’s atmosphere near both the geographic and magnetic equators and at altitudes between 120 and 200 km is called the low-latitude valley region (LLVR) and is among the least understood regions of the ionosphere/thermosphere due to its complex interplay of neutral dynamics, electrodynamics, and photochemistry. Radar studies of the region have revealed puzzling daytime echoes scattered from between 130 and 170 km in altitude. The echoes are quasi-periodic and are observed in solar-zenith-angle dependent layers. Populations with two distinct types of spectral features are observed. A number of radars have shown scattering cross-sections with different seasonal and probing-frequency dependencies. The sources and configurations of the so-called 150-km echoes and the related irregularities have been long-standing riddles for which some solutions are finally starting to emerge as will be described in this review paper. Although the 150-km echoes were discovered in the early 1960s, their practical significance and implications were not broadly recognized until the early 1990s, and no compelling explanations of their generation mechanisms and observed features emerged until about a decade ago. Now, more rapid progress is being made thanks to a multi-disciplinary team effort described here and recent developments in kinetic simulations and theory: 18 of 27 riddles to be described in this paper stand solved (and a few more partially solved) at this point in time. The source of the irregularities is no longer a puzzle as compelling evidence has emerged from simulations and theory, presented since 2016 that they are being caused by photoelectrons driving an upper hybrid plasma instability process. Another resolved riddle concerns the persistent gaps observed between the 150-km scattering layers—we now understand that they are likely to be the result of enhanced thermal Landau damping of the upper hybrid instability process at upper hybrid frequencies matching the harmonics of the electron gyrofrequency. The remaining unsolved riddles, e.g., minute-scale variability, multi-frequency dependence, to name a few, are still being explored observationally and theoretically—they are most likely unidentified consequences of interplay between plasma physics, photochemistry, and lower atmospheric dynamic processes governing the LLVR.

show abstract

First Dual‐Frequency Radar Observations of 150‐km Echoes From Gadanki and Implications

Cited by 3 publications

References 20 publications

Common‐Volume Dual‐Frequency Radar Observations of 150‐km Echoes and Implications

Common‐Volume Dual‐Frequency Radar Observations of 150‐km Echoes and Implications

On the Nature of F‐Region Bottom‐Type Echoing Layer Over Gadanki

Solved and unsolved riddles about low-latitude daytime valley region plasma waves and 150-km echoes

Contact Info

Product

Resources

About