Browsing by Author "Kuyeng, Karim"
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Item Restricted Climatology of Equatorial F-Region UHF Coherent Backscatter Radar Echoes and Comparison with Collocated VHF Radar Observations(IEEE, Institute of Electrical and Electronics Engineers, 2024) Massoud, A. A.; Rodrigues, F. S.; Sousasantos, J.; Milla, M. A.; Scipión, Danny; Apaza, J. M.; Kuyeng, Karim; Padin, C.Equatorial ionospheric irregularities at meter scale sizes have been well-studied using Very High Frequency (VHF) radar systems at the Jicamarca Radio Observatory (JRO). For example, the Jicamarca Unattended Long-Term Studies of the Ionosphere and Atmosphere (JULIA) is a 50 MHz coherent scatter radar system and has operated routinely since 1996. Radio waves transmitted by JULIA reflect off of field-aligned irregularities with scale sizes of ~3-meters due to Bragg scattering. Recently, the deployment and later repair of an Ultra High Frequency (UHF) radar system at the JRO provided an opportunity for coherent backscatter radar studies of irregularities with sub-meter scale sizes. The 14-panel version of the Advanced Modular Incoherent Scatter Radar (AMISR-14) system makes measurements at 445 MHz, corresponding to measurements of previously unobserved ~34-centimeters equatorial irregularities.Item Open Access Climatology of mesosphere and lower thermosphere diurnal tides over Jicamarca (12°S, 77°W): observations and simulations(SpringerOpen, 2023-12-14) Suclupe, Jose; Chau, Jorge L.; Conte, Federico J.; Milla, Marco; Pedatella, N. M.; Kuyeng, KarimThis work shows a 3-year climatology of the horizontal components of the solar diurnal tide, obtained from wind measurements made by a multistatic specular meteor radar (SIMONe) located in Jicamarca, Peru (12°S, 77°W). Our observations show that the meridional component is more intense than the zonal component, and that it exhibits its maxima shifted with respect to the equinox times (i.e., the largest peak occurs in August–September, and the second one in April–May). The zonal component only shows a clear maximum in August–September. This observational climatology is compared to a climatology obtained with the Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X). Average comparisons indicate that the model amplitudes are 50% smaller than the observed ones. The WACCM-X results are also used in combination with observed altitude profiles of the tidal phases to understand the relative contributions of migrating and non-migrating components. Based on this, we infer that the migrating diurnal tide (DW1) dominates in general, but that from June until September (November until July) the DE3 (DW2) may have a significant contribution to the zonal (meridional) component. Finally, applying wavelet analysis to the complex amplitude of the total diurnal tide, modulating periods between 5 and 80 days are observed in the SIMONe measurements and the WACCM-X model. These modulations might be associated to planetary waves and intraseasonal oscillations in the lower tropical atmosphere.Item Open Access Clustering and data reduction algorithm applied to spectra measured with a multi-static HF sounding system in Peru(2023 CEDAR Workshop, 2023-06) Vásquez, V.; Milla, M.; Kuyeng, Karim; Gonzales, J.; Scipión, DannyThe HF radar is a network of HF radio beacons and receivers for ionospheric sounding, and it has been operating in Peru since 2016. The purpose of this instrument is to measure the group delay, Doppler shift, power, and other parameters in order to estimate the regional plasma density as a function of space and time. This information is crucial for forecasting the occurrence of Spread-F. To improve the quality of the spectral data, two changes were made. The first one involved transmitting frequencies separated by 3.3 Hz in each transmission station, which allowed to spectrally separate and identify the signals coming from a given station, displacing the cross-talk in frequency but not eliminating it. Therefore, the second change was made, which corresponds to the development of an algorithm that extracts only the signals of interest from the measured spectrum. It is capable of detecting clusters of data in the spectra classifying them as coherent echoes, while noise sectors are discarded. The algorithm procedure and the comparisons of the spectra and final data are shown in this work.Item Open Access Construcción de un prototipo de radar meteorológico de banda X en el Perú(Instituto Geofísico del Perú, 2020-06) Espinoza, Juan C.; Valdez, Alexander; Ortecho, Daniel; Kuyeng, Karim; Scipión, Danny; Milla, MarcoSe presentan los avances en el desarrollo del primer prototipo de radar meteorológico de banda X completamente desarrollado en el Perú. El sistema es compacto y transportable y cuenta con una antena parabólica de 1.2m de diámetro de doble polarización instalada sobre un posicionador, que permite el movimiento en azimut y elevación. Además, los sistemas de transmisión y recepción del radar están basados en tecnologías SDR (Software Defined Radio) para mayor flexibilidad en su configuración. El objetivo del radar es realizar mediciones de las precipitaciones en una determinada región, cubriendo un área de varias decenas de kilómetros alrededor del radar para así poder realizar investigaciones sobre las condiciones atmosféricas en esta región. La construcción de este prototipo viene siendo realizada por el Instituto Geofísico del Perú, en su sede del Radio Observatorio de Jicamarca, y es financiada por el fondo para intervenciones ante la ocurrencia de desastres naturales (FONDES) del Instituto Nacional de Defensa Civil (INDECI).Item Open Access Driving Influences of the Doppler Flash Observed by SuperDARN HF Radars in Response to Solar Flares(American Geophysical Union, 2022-06) Chakraborty, S.; Qian, L.; Baker, J. B. H.; Ruohoniemi, J. M.; Kuyeng, Karim; Mclnerney, J. M.Sudden enhancement in high-frequency absorption is a well-known impact of solar flare-driven Short-Wave Fadeout (SWF). Less understood, is a perturbation of the radio wave frequency as it traverses the ionosphere in the early stages of SWF, also known as the Doppler flash. Investigations have suggested two possible sources that might contribute to it’s manifestation: first, enhancements of plasma density in the D-and lower E-regions; second, the lowering of the F-region reflection point. Our recent work investigated a solar flare event using first principles modeling and Super Dual Auroral Radar Network (SuperDARN) HF radar observations and found that change in the F-region refractive index is the primary driver of the Doppler flash. This study analyzes multiple solar flare events observed across different SuperDARN HF radars to determine how flare characteristics, properties of the traveling radio wave, and geophysical conditions impact the Doppler flash. In addition, we use incoherent scatter radar data and first-principles modeling to investigate physical mechanisms that drive the lowering of the F-region reflection points. We found, (a) on average, the change in E- and F-region refractive index is the primary driver of the Doppler flash, (b) solar zenith angle, ray’s elevation angle, operating frequency, and location of the solar flare on the solar disk can alter the ionospheric regions of maximum contribution to the Doppler flash, (c) increased ionospheric Hall and Pedersen conductance causes a reduction of the daytime eastward electric field, and consequently reduces the vertical ion-drift in the lower and middle latitude ionosphere, which results in lowering of the F-region ray reflection point.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 First climatology of F-region UHF echoes observed by the AMISR-14 system at the Jicamarca radio observatory and comparison with the climatology of VHF echoes observed by the collocated JULIA radar(Elsevier, 2024-10) Massoud, Alexander A.; Rodrigues, Fabiano S.; Sousasantos, Jonas; Milla, Marco A.; Scipión, Danny; Apaza, Joab M.; Kuyeng, Karim; Padin, CarlosCoherent backscatter radar observations made at the Jicamarca Radio Observatory (JRO) have contributed significantly to our understanding of equatorial F-region irregularities. Radar observations, however, have been made predominantly at the Very-High Frequency (VHF) band (50 MHz), which corresponds to measurements of 3-m field-aligned irregularities. The deployment of the 14-panel version of the Advanced Modular Incoherent Scatter Radar (AMISR-14) at Jicamarca provided an opportunity for observations of Ultra-High Frequency (UHF - 445 MHz) echoes which correspond to measurements of irregularities with 0.34 m scale sizes. Here, we present what we believe to be the first report describing the quiet-time climatology of sub-meter equatorial F-region irregularities derived from UHF radar measurements. The measurements were made between August 2021 and February 2023 using a 10-beam AMISR-14 mode that scanned the F-region in the magnetic equatorial plane. The results show how F-region sub-meter irregularities respond to variations in season and solar flux conditions. The results also confirm, experimentally, that the occurrence of UHF F-region echoes is controlled by the occurrence of equatorial spread F (ESF). Higher occurrence rates were observed during pre-midnight hours and during Equinox and December solstice. Reduced occurrence rates were observed during June solstice. The results show that an increase in solar flux was followed by an increase in the altitude where noticeable occurrence rates start and in the maximum altitude of these occurrence rates. The observations also show that occurrence rates lasted longer (in local time) during low solar flux conditions. Comparisons with collocated VHF radar observations showed that, despite differences in radar parameters, observation days, and the scale size (one order of magnitude) of the scattering irregularities, the two systems show similar climatological variations with only minor differences in the absolute occurrence rates. Finally, the analysis of the occurrence rates for different beams did not show substantial climatological variations over local (within a few 100s of km) zonal distances around JRO. We point out, however, that observations on a single day can show strong local variations in echo detection and intensity within the AMISR-14 field of view due to the intrinsic development and decay of ESF structures.Item Open Access Jicamarca Radio Observatory 2021 Status(Instituto Geofísico del Perú, 2021-06) Milla, Marco; Kuyeng, Karim; Espinoza, Juan C.; De la Jara, CésarThe Jicamarca Radio Observatory is a research facility of the Geophysical Institute of Peru dedicated to the study of the equatorial ionosphere and upper atmosphere. It is located near the city of Lima, Peru. Its main instrument is one of the largest Incoherent Scatter radars in the World. This presentation explains: Jicamarca radar status, news about AMISR14 and SIMONe and radar upgrade progress.Item Open Access Jicamarca Radio Observatory status during COVID-19(Instituto Geofísico del Perú, 2020-06-25) Milla, Marco; Kuyeng, Karim; Espinoza, Juan C.; De la Jara, CésarIn this presentation, Dr. Marco Milla, director of the Jicamarca Radio Observatory, explained the state of the Jicamarca radar and the progress in the improvements that will be implemented to increase its capabilities. This seeks to develop new experiments and attract new users for the radar.Item Open Access Multistatic specular meteor radar network in Peru: system description and initial results(American Geophysical Union, 2021-01) Chau, J. L.; Urco, J. M.; Vierinen, J.; Harding, B. J.; Clahsen, M.; Pfeffer, N.; Kuyeng, Karim; Milla, Marco; Erickson, P. J.The mesosphere and lower thermosphere (MLT) region is dominated globally by dynamics at various scales: planetary waves, tides, gravity waves, and stratified turbulence. The latter two can coexist and be significant at horizontal scales less than 500 km, scales that are difficult to measure. This study presents a recently deployed multistatic specular meteor radar system, SIMONe Peru, which can be used to observe these scales. The radars are positioned at and around the Jicamarca Radio Observatory, which is located at the magnetic equator. Besides presenting preliminary results of typically reported large‐scale features, like the dominant diurnal tide at low latitudes, we show results on selected days of spatially and temporally resolved winds obtained with two methods based on: (a) estimation of mean wind and their gradients (gradient method), and (b) an inverse theory with Tikhonov regularization (regularized wind field inversion method). The gradient method allows improved MLT vertical velocities and, for the first time, low‐latitude wind field parameters such as horizontal divergence and relative vorticity. The regularized wind field inversion method allows the estimation of spatial structure within the observed area and has the potential to outperform the gradient method, in particular when more detections are available or when fine adaptive tuning of the regularization factor is done. SIMONe Peru adds important information at low latitudes to currently scarce MLT continuous observing capabilities. Results contribute to studies of the MLT dynamics at different scales inherently connected to lower atmospheric forcing and E‐region dynamo related ionospheric variability.Item Open Access On new two-dimensional UHF radar observations of equatorial spread F at the Jicamarca Radio Observatory(Springer Open, 2023-08-09) Rodrigues, F.S.; Milla, M.A.; Scipión, Danny; Apaza, Joab; Kuyeng, Karim; Sousasantos, J.; Massoud, A.A.; Padin, C.We describe a mode for two-dimensional UHF (445 MHz) radar observations of F-region irregularities using the 14-panel version of the advanced modular incoherent scatter radar (AMISR-14). We also present and discuss examples of observations made by this mode. AMISR-14 is installed at the Jicamarca Radio Observatory (JRO, 11.95°S, 76.87°W, ~ 0.5° dip latitude) in Peru and, therefore, allows studies of ionospheric irregularities at the magnetic equator. The new mode takes advantage of the electronic beam-steering capability of the system to scan the equatorial F-region in the east–west direction. Therefore, it produces two-dimensional views of the spatial distribution of sub-meter field-aligned density irregularities in the magnetic equatorial plane. The scans have a temporal resolution of 20 s and allow observations over a zonal distance of approximately 400 km at main F-region heights. While the system has a lower angular and range resolution than interferometric in-beam VHF radar imaging observations available at Jicamarca, it allows a wider field-of-view than that allowed with the VHF system. Here, we describe the mode, and present and discuss examples of observations made with the system. We also discuss implications of these observations for studies of ESF at the JRO.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 Open Access Preliminary results of new operation mode JULIA Medium Power at JRO(2023 CEDAR Workshop, 2023-06) Kuyeng, Karim; Scipión, Danny; Condor, P.; Manay, E.; Milla, M.The main radar of the Jicamarca Radio Observatory (JRO), for several years, has operated with two main modes, the ISR mode with big transmitters (1.5 MW), operating around 1000 hours per year, to survey the ionosphere and obtain parameters such as drifts, densities and composition; and the JULIA mode with low power transmitters (20 kW), operating around 4000 hours per year, to measure mostly coherent echoes such as Equatorial Electrojet, Spread F and 150 km echoes to provide with a proxy of the behavior of the ionosphere. Starting in 2022, two new solid-state transmitters were installed at JRO, with peak power of 96 kW each, making it possible to not only detect coherent echoes but to be able to estimate zonal and vertical drifts in the ionosphere too. This new mode, called JULIA Medium Power (JULIA MP), is capable of measuring the same coherent echoes as the original JULIA but able to estimate zonal and vertical drifts up to 500 km. This work will present the preliminary results of this mode, comparisons of the coherent echoes obtained with JULIA and JULIA MP and finally show the quality of drifts we are getting with this medium power mode.Item Open Access Quality improvements to the spectral data acquired from HF multi-static sounding system at the magnetic Equator(2023 SWOL Workshop, 2023-10) Vásquez, V.; Milla, M.; Kuyeng, Karim; Gonzales, J.; Scipión, DannyA network of HF radio beacons and receivers for ionospheric sounding has been operating in Peru since 2016. The purpose of this instrument is to measure the group delay, Doppler shift, power, and other parameters in order to estimate the regional plasma density as a function of space and time, this information is crucial for forecasting the occurrence of Spread-F. The HF radar used only one frequency for transmission and reception that generated interference between different transmitter stations in the analyzed spectrum. To improve the quality of the spectral data, changes were made to the operation of the radar. Spectral separation of the transmitted signals was carried out, followed by the implementation of an algorithm that extracts only the signals of interest from the measured spectrum, discarding the noisy areas. The procedure for the changes made to the HF system, along with comparisons of the final data, is shown in this work.Item Open Access Radar imaging comparison methods(Instituto Geofísico del Perú, 2021-06) Yupanqui, Diego; Milla, Marco; Kuyeng, Karim; Ocaña, Eladio; Oré, ErnestoIn this work, we are conducting a comparison of different methods to solve a one-dimensional aperture-synthesis radar imaging problem based on simulations. For this purpose, we are going to consider the geometry of the Jicamarca ionospheric radar. These methods are going to be applied to the generation of images of field-aligned plasma irregularities in the equatorial ionosphere, particularly, to the case of Spread-F phenomena. The methods used in the comparison goes from a direct Fourier inversion and a simple numerical integration, to more elaborated algorithms, such as, Capon’s method and Maximum entropy method. We are also going to include in the comparison, the compressed sensing technique using the Haar and dab4 basis, in this case, we are assuming that the brightness function of the spread-F echoes has a sparse representation. In the simulations of the radar measurements, we are considering Gaussian shape brightness functions. The different methods will be compared based on some metrics of the reconstructed images.Item Open Access Short-term prediction of horizontal winds in the mesosphere and lower thermosphere over coastal Peru using a hybrid model(Frontiers Media, 2024-09-23) Mauricio, Christian; Suclupe, Jose; Milla, Marco; López de Castilla, Carlos; Kuyeng, Karim; Scipión, Danny; Rodriguez, RodolfoThe mesosphere and lower thermosphere (MLT) are transitional regions between the lower and upper atmosphere. The MLT dynamics can be investigated using wind measurements conducted with meteor radars. Predicting MLT winds could help forecast ionospheric parameters, which has many implications for global communications and geo-location applications. Several literature sources have developed and compared predictive models for wind speed estimation. However, in recent years, hybrid models have been developed that significantly improve the accuracy of the estimates. These integrate time series decomposition and machine learning techniques to achieve more accurate short-term predictions. This research evaluates a hybrid model that is capable of making a short-term prediction of the horizontal winds between 80 and 95 km altitudes on the coast of Peru at two locations: Lima (12°S, 77°W) and Piura (5°S, 80°W). The model takes a window of 56 data points as input (corresponding to 7 days) and predicts 16 data points as output (corresponding to 2 days). First, the missing data problem was analyzed using the Expectation Maximization algorithm (EM). Then, variational mode decomposition (VMD) separates the components that dominate the winds. Each resulting component is processed separately in a Long short-term memory (LSTM) neural network whose hyperparameters were optimized using the Optuna tool. Then, the final prediction is the sum of the predicted components. The efficiency of the hybrid model is evaluated at different altitudes using the root mean square error (RMSE) and Spearman’s correlation (r). The RMSE ranged from 10.79 to 27.04 ms⁻¹, and the correlation ranged from 0.55 to 0.94. In addition, it is observed that the prediction quality decreases as the prediction time increases. The RMSE at the first step reached 6.04 ms⁻¹ with a correlation of 0.99, while at the sixteenth step, the RMSE increased up to 30.84 ms⁻¹ with a correlation of 0.5.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.Item Open Access The impact of the Hunga Tonga–Hunga Ha’apai volcanic eruption on the Peruvian atmosphere: from the sea surface to the ionosphere(SpringerOpen, 2024-05-28) Pacheco, Edgardo E.; Velasquez, J. P.; Flores, R.; Condori, L.; Fajardo, G.; Kuyeng, Karim; Scipión, Danny; Milla, M.; Conte, J. F.; Poblet, F. L.; Chau, J. L.; Suclupe, J.; Rojas, R.; Manay, E.The eruption of the Hunga Tonga Hunga Ha’apai volcano on 15 January 2022 significantly impacted the lower and upper atmosphere globally. Using multi-instrument observations, we described disturbances from the sea surface to the ionosphere associated with atmospheric waves generated by the volcanic eruption. Perturbations were detected in atmospheric pressure, horizontal magnetic field, equatorial electrojet (EEJ), ionospheric plasma drifts, total electron content (TEC), mesospheric and lower thermospheric (MLT) neutral winds, and ionospheric virtual height measured at low magnetic latitudes in the western South American sector (mainly in Peru). The eastward Lamb wave propagation was observed at the Jicamarca Radio Observatory on the day of the eruption at 13:50 UT and on its way back from the antipodal point (westward) on the next day at 07:05 UT. Perturbations in the horizontal component of the magnetic field (indicative of EEJ variations) were detected between 12:00 and 22:00 UT. During the same period, GNSS-TEC measurements of traveling ionospheric disturbances (TIDs) coincided approximately with the arrival time of Lamb and tsunami waves. On the other hand, a large westward variation of MLT winds occurred near 18:00 UT over Peru. However, MLT perturbations due to possible westward waves from the antipode have not been identified. In addition, daytime vertical plasma drifts showed an unusual downward behavior between 12:00 and 16:00 UT, followed by an upward enhancement between 16:00 and 19:00 UT. Untypical daytime eastward zonal plasma drifts were observed when westward drifts were expected. Variations in the EEJ are highly correlated with perturbations in the vertical plasma drift exhibiting a counter-equatorial electrojet (CEEJ) between 12:00 and 16:00 UT. These observations of plasma drifts and EEJ are, so far, the only ground-based radar measurements of these parameters in the western South American region after the eruption. We attributed the ion drift and EEJ perturbations to large-scale thermospheric wind variations produced by the eruption, which altered the dynamo electric field in the Hall and Pedersen regions. These types of multiple and simultaneous observations can contribute to advancing our understanding of the ionospheric processes associated with natural hazard events and the interaction with lower atmospheric layers.