Study of sporadic E layers based on GPS radio occultation measurements and digisonde data over the Brazilian region

Resende, L. C. A.; Arras, Christina; Batista, I. S.; Denardini, Clezio Marcos; Bertollotto, T. O.; Moro, Juliano

doi:10.5194/angeo-36-587-2018

Cited by 33 publications

(23 citation statements)

References 26 publications

(40 reference statements)

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“…The blanketing frequency f b Es corresponds to the lowest frequency that can penetrate the Es layer, so it is a measure of the weakest patches of ionization (Yu et al 2015). Arras and Wickert (2018) revealed a linear relationship between S4max and f b Es based on 17 coinciding measurements at mid-latitudes, which is consistent with the results over the Brazilian low-latitude region (Resende et al 2018). Whalen (2009) quantified 47 determinations of S4max, which have a linear dependence on the coinciding electron density (equivalently, the square of the electron plasma frequency f 2 ).…”

Section: Resultssupporting

confidence: 84%

Using GNSS radio occultation data to derive critical frequencies of the ionospheric sporadic E layer in real time

Scott

Xue

et al. 2020

GPS Solut

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The small-scale electron density irregularities in the ionosphere have a significant impact on the interruptions of Global Navigation Satellite System (GNSS) navigation and the accuracy of GNSS positioning techniques. The sporadic ionospheric E (Es) layer significantly contributes to the transient interruptions of signals (loss of lock) for GNSS tracking loops. These effects on the GNSS radio occultation (RO) signals can be used to derive the global location and intensity of Es layers as a complement to ground-based observations. Here we conduct statistical analyses of the intensity of Es layers, based on the scintillation index S4max from the FORMOSAT-3/COSMIC during the period 2006–2014. In comparison with simultaneous observations from an ionosonde network of five low-to-middle latitude ionosondes, the S4max indices from COSMIC, especially the small values, are linearly related to the critical frequency of Es layers (foEs). An accumulated period of less than 1 h is required to derive the short-term variations in real-time ionospheric Es layers. A total of 30.22%, 69.57% and 98.13% coincident hourly foEs values have a relative difference less than 10%, 30% and 100%. Overall, the GNSS RO measurements have the potential to provide accurate hourly observations of Es layers. Observations with S4max < 0.4 (foEs < 3.6 MHz), accounting for 66% of COSMIC S4 measurements, have not been used fully previously, as they are not easily visible in ground-based ionosonde data.

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Section: Resultssupporting

confidence: 84%

Using GNSS radio occultation data to derive critical frequencies of the ionospheric sporadic E layer in real time

Scott

Xue

et al. 2020

GPS Solut

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“…The radio occultation (RO) technology implemented by the FORMOSAT-3/COSMIC satellites can be applied to measure the ionospheric electron density profile including the peak electron density in E-region (N m E). The N m E values calculated from f b Es were seen to be close to the COSMIC N m E values (Arras & Wickert, 2018;Resende et al, 2018). Thus, the periodic peaks on the f b Es curve imply that the periodic disturbance may pass by and enhance the peak electron density in Es.…”

Section: 1029/2019ja027532supporting

confidence: 59%

A Case Study of the Daytime Intense Radar Backscatter and Strong Ionospheric Scintillation Related to the Low‐Latitude E‐Region Irregularities

et al. 2020

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The special daytime echoes, which present the V‐shaped echo pattern between 90–180 km ranges in the range‐time‐intensity (RTI) plot, were occasionally recorded by the Hainan coherent scatter phased array radar (HCOPAR) located at the low latitude of China. Four cases with distinct echo traces are presented to display the common characteristics of the V‐shaped echoes. They usually occur between 10:00–15:00 LT in the daytime with the enhanced top frequency and blanketing frequency of Es layer (ftEs and fbEs). Their left/right wings present negative/positive Doppler velocity. A case on 16 August 2015 was investigated by the joint observation of the HCOPAR, the Hainan Digisonde, and a scintillation receiver. The echo spectra show that the V‐shaped echoes were backscattered from the type 2 irregularities. The formation of the V‐shaped echo pattern was due to the leakage of the antenna sidelobe for the very intense scatter from Es layer. The irregularities were found traveling westward with the velocity of 41.12 ± 2.08 m/s. While the occurrence of the intense irregularities, there were periodic peaks appearing on the ftEs and fbEs curves, and the maximum ftEs‐fbEs reached 10.31 MHz. At the same time, the strong ionospheric scintillation event was recorded by the scintillation receiver. The wind shear is considered to produce the sharp density gradient in the Es plasma and then induce the gradient drift instability. The large‐scale gravity waves have the possibility to induce the E‐region wind shear.

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“…The height where the SNR value deviates most from the mean of the SNR profile is considered as the altitude of the E S layer. This has been validated by comparisons with ionosonde E S observations (Arras and Wickert, 2018;Resende et al, 2018a). 2014obtained from a more limited dataset.…”

Section: Sporadic E Occurrence Ratesmentioning

confidence: 67%

Quarterdiurnal signature in sporadic E occurrence rates and comparison with neutral wind shear

Jacobi¹,

Arras²,

Geißler³

et al. 2018

Preprint

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Abstract. The GPS radio occultation (RO) technique is used to study sporadic E (ES) layer plasma irregularities of the Earth’s ionosphere on a global scale using GPS signal-to-noise ratio (SNR) profiles from the COSMIC/FORMOSAT-3 satellite. The maximum deviation from the mean SNR can be attributed to the height of the ES layer. ES are generally accepted to be produced by ion convergence due to vertical wind shear in the presence of a horizontal component of the Earth magnetic field, while the wind shear is provided mainly by solar tides. Here we present analyses of quarterdiurnal (QDT) signatures in ES occurrence rates. We find from a local comparison with mesosphere/lower thermosphere wind shear obtained with a meteor radar at Collm (51:3°N, 13:0°E), that the phases of the QDT in ES agree well with those of negative wind shear for all seasons except for summer, when the QDT amplitudes are small. We also compare the global QDT ES signal with numerical model results. The global distribution of ES occurrence rates qualitatively agrees with the modeled zonal wind shears. The results indicate that zonal wind shear is indeed an important driving mechanism for the QDT seen in ES.

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Study of sporadic E layers based on GPS radio occultation measurements and digisonde data over the Brazilian region

Cited by 33 publications

References 26 publications

Using GNSS radio occultation data to derive critical frequencies of the ionospheric sporadic E layer in real time

Using GNSS radio occultation data to derive critical frequencies of the ionospheric sporadic E layer in real time

A Case Study of the Daytime Intense Radar Backscatter and Strong Ionospheric Scintillation Related to the Low‐Latitude E‐Region Irregularities

Quarterdiurnal signature in sporadic E occurrence rates and comparison with neutral wind shear

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