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Molina, Maria Graciela
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Molina, Maria Graciela
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- PublicationOpen AccessSome considerations for different time-domain signal processing of pulse compression radar(2010)
; ; ; ; ; ; ; ;Cabrera, M. A.; Universidad Nacional de Tucumán ;Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Ezquer, R. G.; Universidad Nacional de Tucumán ;Sciacca, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Lopez, J. M.; Universidad Tecnológica Nacional, Tucumán ;Molina, M. G.; Universidad Nacional de Tucumán ;Baskaradas, J. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ;; ; ; Radar technology has for a long time used various systems that allow detection under high-resolution conditions, while emitting at the same time low peak power. Among these systems, transmitted pulse encoding by means of biphasic codes has been used for the advanced ionospheric sounder that was developed by the AIS-INGV ionosonde. In the receiving process, suitable decoding of the signal must be accomplished. This can be achieved in both the time and the frequency domains. Focusing on the time domain, different approaches are possible. In this study, two of these approaches have been compared, using data acquired by the AIS-INGV and processed by means of software tools (mainly Mathcad©). The analysis reveals the differences under both noiseless and noisy conditions, although this does not allow the conclusive establishment as to which method is better, as each of them has benefits and drawbacks.658 222 - PublicationRestrictedConsequences of a Solar Wind Stream Interaction Region on the Low Latitude Ionosphere: Event of 7 October 2015(2020)
; ; ; ; ; ; ; ; ; ; ; In this article, we present a study of the perturbations occurring in the Earth’s environment on 7 October 2015. We use a multi-instrument approach, including space and ground observations. In particular, we study the ionospheric conditions at low latitudes. Two ionospheric storms are observed at the low latitude station of Tucumán (26° 51' S, 65° 12' W). We observe a negative ionospheric storm followed by a positive one. These ionospheric perturbations were triggered by two sudden storm commencements (SSCs) of a strong geo-magnetic storm. Preliminary results show that the main mechanism involved in both ionospheric storms is the prompt penetration of electric fields (PPEFs) from the magnetosphere. Furthermore, in the positive storm, disturbed dynamo electric fields are observed acting in combination with the PPEFs. The impact of the solar wind on the Earth’s environment is analyzed using geomagnetic data and proxies, combined with data acquired in the Tucumán Low Latitude Observatory for the Upper Atmosphere. We also investigate the solar and interplanetary drivers of this intense perturbation. We find that, although typically interplanetary coronal mass ejections (ICMEs) are the most geoeffective transient interplanetary events, in this case, a corotating interaction region (CIR) is responsible for these strong perturbations to the geospace.163 5 - PublicationOpen AccessParticle classification in the LAGO water Cherenkov detectors using clustering algorithmsThe Latin American Giant Observatory (LAGO) is a ground-based observatory studying solar or high-energy astrophysics transient events. LAGO takes advantage of its distributed network of Water Cherenkov Detectors (WCDs) in Latin America as a tool to measure the secondary particle flux reaching the ground. These secondary particles are produced during the interaction between the modulated cosmic rays flux and the atmosphere. The LAGO WCDs are sensitive to secondary charged particles, high energy photons through pair creation and Compton scattering, and even neutrons thanks to, e.g., the deuteration of protons in the water volume. The pulse shape generated by these particles depends on several factors, such as the detector geometry, the water purity, the sensor response, or the reflectivity and diffusivity of the inner coating. Due to the decentralized nature of LAGO, these properties are different for each node. Additionally, the pulse shape depends on the convolution between the response of the central photomultiplier (PMT) to individual photons and the time distribution of the Cherenkov photons reaching the PMT. Typically, a WCD gives pulses with a sharp rise time ( 10 ns) and a longer decay time ( 70 ns). In this work, the WCD data used is acquired using the original LAGO data-acquisition system that digitizes pulses at a sampling rate of 40 MHz and 10 bits resolution on time windows of 400 ns. Here, we apply unsupervised machine learning techniques to find patterns in the WCDs data and subsequently create groups, through clustering, that can be used to provide particle separation. We use data acquired from an individual WCD, showing that density-based clustering algorithms are suitable for automatic particle separation producing good candidate groups. Improved separation would help LAGO to reconstruct in situ the properties of primary cosmic rays flux. These results open the possibility to deploy machine learning-based models in our distributed detection network for onboard data analysis as an operative prototype, allowing detectors to be installed at very remote sites.
38 12 - PublicationRestrictedAutomatic ionospheric layers detection: Algorithms analysis(2016)
; ; ; ; ; ; ;Molina, M. G.; Dpto. de Ciencias de la Computacion FACET-UNT, Tucuman, Argentina ;Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Cabrera, M. A.; Dpto. de Electronica Electricidad y Computacio FACET-UNT, Tucuman, Argentina ;Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Sciacca, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Baskaradas, J. A.; School of Electrical and Electronics Engineering, SASTRA University, Thanjavur, India; ; ; ; ; Vertical sounding is a widely used technique to obtain ionosphere measurements, such as an estimation of virtual height versus frequency scanning. It is performed by high frequency radar for geophysical applications called "ionospheric sounder” (or "ionosonde”). Radar detection depends mainly on targets characteristics. While several targets behavior and correspondent echo detection algorithms have been studied, a survey to address a suitable algorithm for ionospheric sounder has to be carried out. This paper is focused on automatic echo detection algorithms implemented in particular for an ionospheric sounder, target specific characteristics were studied as well. Adaptive threshold detection algorithms are proposed, compared to the current implemented algorithm, and tested using actual data obtained from the Advanced Ionospheric Sounder (AIS-INGV) at Rome Ionospheric Observatory. Different cases of study have been selected according typical ionospheric and detection conditions.581 45 - PublicationOpen AccessIonospheric response modeling under eclipse conditions: Evaluation of 14 December 2020, total solar eclipse prediction over the South American sector(2022)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;In this work, we evaluate the SUPIM-INPE model prediction of the 14 December 2020, total solar eclipse over the South American continent. We compare the predictions with data from multiple instruments for monitoring the ionosphere and with different obscuration percentages (i.e., Jicamarca, 12.0°S, 76.8°W, 17%; Tucumán 26.9°S, 65.4° W, 49%; Chillán 36.6°S, 72.0°W; and Bahía Blanca, 38.7°S, 62.3°W, reach 95% obscuration) due to the eclipse. The analysis is done under total eclipse conditions and non-total eclipse conditions. Results obtained suggest that the model was able to reproduce with high accuracy both the daily variation and the eclipse impacts of E and F1 layers in the majority of the stations evaluated (except in Jicamarca station). The comparison at the F2 layer indicates small differences (<7.8%) between the predictions and observations at all stations during the eclipse periods. Additionally, statistical metrics reinforce the conclusion of a good performance of the model. Predicted and calibrated Total Electron Content (TEC, using 3 different techniques) are also compared. Results show that, although none of the selected TEC calibration methods have a good agreement with the SUPIM-INPE prediction, they exhibit similar trends in most of the cases. We also analyze data from the Jicamarca Incoherent Scatter Radar (ISR), and Swarm-A and GOLD missions. The electron temperature changes observed in ISR and Swarm-A are underestimated by the prediction. Also, important changes in the O/N2 ratio due to the eclipse, have been observed with GOLD mission data. Thus, future versions of the SUPIM-INPE model for eclipse conditions should consider effects on thermospheric winds and changes in composition, specifically in the O/N2 ratio.45 36 - PublicationRestrictedDigital signal processing and numerical analysis for radar in geophysical applications(2013-05-15)
; ; ; ; ; ;Molina, M. G.; Dpto. de Ciencias de la Computación, Facultad de Ciencias Exactas y Tecnología (FACET), Universidad Nacional de Tucumán (UNT), Av. Independencia 1800, Tucumán, Argentina ;Cabrera, M. A.; Laboratorio de Telecomunicaciones, Dpto. de Electrónica Electricidad y Computación, FACET, UNT, Av. Independencia 1800, Tucumán, Argentina ;Ezquer, R. G.; Laboratorio de Ionósfera, Dpto. de Física, FACET, UNT, Av. Independencia 1800, Tucumán, Argentina ;Fernandez, P. M.; Dpto. de Ciencias de la Computación, Facultad de Ciencias Exactas y Tecnología (FACET), Universidad Nacional de Tucumán (UNT), Av. Independencia 1800, Tucumán, Argentina ;Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ;; Numerical solutions for signal processing are described in this work as acontribution to study of echo detection methods for ionospheric sounder design. The ionospheric sounder is a high frequency radar for geophysical applications. The main detection approach has been done by implementing the spread-spectrum techniques using coding methods to improve the radar’s range resolution by transmitting low power. Digital signal processing has been performed and the numerical methods were checked. An algorithm was proposed and its computational complexity was calculated. The proposed detection process combines two channels correlations with the local code and calculates threshold (Vt) by statistical evaluation of the background noise to design a detection algorithm. The noisy signals treatment was performed depending on the threshold and echo amplitude. In each case, the detection was improved by using coherent integration. Synthetic signals, close loop and actual echoes, obtained from the Advanced Ionospheric Sounder (AIS-INGV) at Rome Ionospheric Observatory, were used to verify the process. The results showed that, even in highly noisy environments, the echo detection is possible. Given that these are preliminary results, further studies considering data sets corresponding to other geophysical conditions are needed.621 85