Browsing by Author "Flores, Roberto"
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Item Open Access Estimation of spectral parameters from oblique Equatorial Electrojet echoes using a double skewed Gaussian model at JRO(2023 CEDAR Workshop, 2023) Flores, Roberto; Milla, M.; Kuyeng, Karim; Hysell, D.L.; Chau, J.L.Coherent echoes from the equatorial electrojet (EEJ) region are detected at the Jicamarca Radio Observatory (JRO) by using an array of 16 Yagi antennas with a main beam pointed obliquely to the west with an elevation of about 35 deg. The spectrum of these observations are composed of two types of EEJ echoes (Type I and Type II)[1] from which we can estimate their main spectral parameters such as Doppler shift and spectral width independently for each type. Previously, the method applied to obtain these parameters was a standard fitting approach based on a double Gaussian model. However, in some cases, the shape of the spectral measurements are not symmetric (resembling the shape of a skewed distribution). Based on simulations, we determined that the skewed shape of the oblique EEJ spectrum comes from the fact that the measured spectrum is the result of the sum of spectral contributions coming from different heights, with different Doppler shifts and spectral widths weighted by the antenna beam shape. The overall result is an asymmetric spectrum with a peak that does not coincide with the average Doppler shift. Thus in order to account for this effect, we have implemented a double skewed Gaussian distribution model to fit the oblique EEJ measurements and estimate their spectral parameters. In this work, we present the results obtained in the simulation showing the skewed shape of the spectrum. Based on our simulations, we have also proved that the shift of the skewed Gaussian model can be interpreted as the Doppler shift of the echoes. In addition, some examples of the new fitting procedure are shown in comparison with the classical Gaussian fitting where it can be seen the better agreement between the data and the double skewed Gaussian model.Item Open Access Inferring Zonal Wind Profiles in the Equatorial Electrojet From Coherent Scatter(URSI, 2022-10-16) Hysell, D.L.; Chau, J.L.; Conte, J.F.; Flores, Roberto; Milla, M.A.Zonal wind estimates in the equatorial electrojet derived from coherent scatter echoes, specular meteor trail echoes, and optical limb scans are compared. While the three techniques exhibit broad overall agreement, significant differences in the results of the three techniques appear. The differences can be attributed in large part to horizontal inhomogeneity in the winds and the dissimilar averaging kernels of the three techniques.Item Open Access Long term analysis of high-resolution E-region neutral wind estimations over Jicamarca: First results(2024 CEDAR Workshop, 2024-06) Flores, Roberto; Milla, M.; Hysell, D. L.Ground based techniques can be used to measure neutral zonal winds, such as the ISR technique which is usually performed to estimate zonal wind profiles from measured ion drifts at mid- and high-latitude but cannot be used at low-latitudes due to clutter from coherent echoes at E-layer (EEJ). Additionally, the Spread Spectrum Interferometric Multistatic meteor radar Observing Network (SIMONe) system, deployed in September 2019, can estimate neutral winds from specular meteor trail echoes in the mesosphere and lower thermosphere (MLT) region (70 - 110 km) which includes the EEJ layer, however the time resolution is 1 hour and it probes a larger volume than our oblique radar, then estimated winds will be a result of a contribution from different regions. Space-based missions have also been used to measure these winds such as the Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI) on board the ICON satellite, the Wind Imaging Interferometer (WINDII) on the Upper Atmosphere Research Satellite (UARS) among others, but their measurements are not continuous over a specific latitude and longitude as they orbit around the planet. On the other hand, a technique to estimate zonal neutral winds from oblique EEJ type II Doppler shifts, sampled every minute approximately, was proposed by Shume et al. [2005]. This method predicts Doppler shifts from neutral winds, compares the Doppler with the measured ones and updates the winds until the best data-model agreement of the Doppler shift (RMSE≤2.0). Although wind estimations are limited to the EEJ echoes detection and SNR intensity, this method provides high time resolution wind profiles from 97 to 107 km approximately and might be complemented by other techniques. This work presents the first results of neutral wind estimations over the Jicamarca Radio Observatory (JRO), a facility of Instituto Geofísico del Perú (IGP), at the EEJ region with a resolution of 5 minutes and 700 meters using oblique spectra data fitted by a skewed Gaussian distribution.Item Open Access Preliminary AMISR-14 radar observations of F-region incoherent backscatter echoes at the Jicamarca Radio Observatory (JRO)(2022 CEDAR Workshop, 2022-06) Apaza, Joab; Kuyeng, Karim; Flores, Roberto; Milla, M.; Rodrigues, F. S.; Scipión, DannyA 14-panel Advanced Modular Incoherent Scatter Radar (AMISR-14) was installed at the Jicamarca Radio Observatory (IGP- JRO) in 2014. Because of its size, this radar was mainly used to observe coherent echoes such as those produced by the Equatorial Electrojet (EEJ) and Equatorial Spread F (ESF). However, the radar operation was intermittent until 2019 when repairs started to make the radar fully operational. Now, AMISR-14 runs regularly in parallel with the main Jicamarca radar in the JULIA (Jicamarca Unattended Long-term studies of the Ionosphere and Atmosphere) mode to monitor the Equatorial Spread F activity. More recently, we found that running these experiments with a more stable peak power, we have been able to detect not only coherently scatter (CS) signals but also what seems to be incoherently scattered (IS) echoes from the F-region ionosphere. In this poster, we will present some examples of the experiments we have been conducting with AMISR-14. More specifically, we will present and discuss examples of these interesting ISR-like echoes observed with AMISR-14 pointing in different directions along the E-W plane.Item Restricted Spectral Analysis of Incoherent Scatter Radar Signals in Faraday/Double Pulse Experiments at the Jicamarca Radio Observatory(IEEE, Institute of Electrical and Electronics Engineers, 2021) Flores, Roberto; Milla, Marco; Kuyeng, KarimThe Jicamarca incoherent scatter radar can be operated in different modes to measure the main physical parameters of the equatorial ionosphere. One of these modes is the Faraday/Double Pulse experiment that was designed to estimate F -region plasma densities and electron/ion temperatures by pointing the Jicamarca antenna beam off-perpendicular to the geomagnetic field. For several years, the data processing for this mode was performed in time domain (correlation analysis), but sometimes the data is contaminated with frequency interference and other unwanted signals that are not easy to remove. To obtain better results, a spectral analysis procedure for this mode has been implemented in Signal Chain, a python-based radar signal processing library developed at the Jicamarca Radio Observatory. Signal Chain includes algorithms for interference and clutter removal to clean the spectral data before estimating the geophysical parameters. The procedure applies an outlier removal algorithm before calculating incoherently averaged power spectra. This algorithm, based on the Hildebrand-Sekhon method, is applied to sequences of spectral data for each frequency bin. Then, the DC clutter from the self- and cross-spectra is removed as a second step in the cleaning process. In this work, we present the results obtained with the spectral analysis procedure applied to the the FaradaylDouble Pulse experiment and compared the electron densities estimated with this method with the ones obtained with the standard correlation analysis.