Navegando por Autor "Macedo, Humberto Gimenes"
Agora exibindo 1 - 8 de 8
Resultados por página
Opções de Ordenação
Item Ahead-of-Tsunami magnetic disturbance detection using intrinsic mode functions: Tohoku-Oki earthquake case study(Springer Nature Link) Oliveira, Virgínia Klausner de; Macedo, Humberto Gimenes; Prestes, AlanWe document magnetic disturbances that occurred during the Tohoku-Oki tsunami of 11 March 2011 using empirical mode decomposition (EMD) in a dataset derived from a network of ground-based magnetometers (INTERMAGNET and GIS). The disturbances, obtained by filtering the magnetic field data using the first intrinsic mode function (IMF1) of EMD, propagate ahead of the tsunami at a speed in the range of 600–1.6 km/s. They also appear 3 min (near-field) to 2 h (far-field) earlier than the tsunami arrival at the magnetic observatories. We refer to these distur- bances as ahead-of-tsunami magnetic disturbances (ATMDs). A comparison with seismometer data shows them arriving 10 min after the arrival of Rayleigh waves. Their association with both seismogenic and tsunamigenic processes is discussed, and it is argued that the tsunamigenic process can well explain the magnetic disturbance propagation characteristics at the far-field. At near- field, the ATMDs are the coseismic magnetic signatures mainly driven by surface Rayleigh waves. Monitoring these ATMDs can be extremely useful for the early warning of the tsunami.Item Análise de componentes principais aplicada à dendrocronologiaSilva, Daniela Oliveira da; Oliveira, Virgínia Klausner de; Prestes, Alan; Macedo, Humberto GimenesItem Desenvolvimento de Ferramentas Computacionais para o Estudo de Variações Geomagnéticas e de Distúrbios Ionosféricos Propagantes(2022-03-11) Oliveira, Virgínia Klausner de; Muella, Marcio Tadeu de Assis Honorato; Gomes, Anna Beatriz Silva; Cândido, Claudia Maria Nicoli; Macedo, Humberto Gimenes; Prestes, Alan; São José dos CamposEsta dissertação aborda as assinaturas geomagnéticas e ionosféricas causadas por eventos solares, sísmicos e oceânicos. A atividade solar, principalmente as ejeções de massa coronal e as regiões de interação corrotantes, podem gerar variações geomagnéticas na forma de tempestades magnéticas e eventos HILDCAA em virtude do acoplamento entre a magnetosfera e o vento solar. Por outro lado, durante a ocorrência de terremotos tsunamigênicos verifica-se o desenvolvimento de ondas de gravidade na atmosfera neutra, pois a gravidade atua como uma força restauradora a fim de reestabelecer o equilíbrio após a perturbação inicial. Estas, por sua vez, propagam-se até a termosfera, onde interagem com o plasma ionosférico por meio de colisões entre íons e neutros, produzindo correntes elétricas e campos magnéticos secundários. Consequentemente, variações geomagnéticas irregulares são produzidas, com períodos e amplitudes na ordem de minutos e poucos nT , respectivamente. Além disso, devido ao fenômeno de indução por movimento, os fluxos oceânicos associados a um tsunami também geram variações geomagnéticas, tendo em vista que as águas oceânicas constituem um fluido condutor em movimento que está imerso no campo geomagnético. Em altitudes ionosféricas, as ondas de gravidade colocam a ionosfera em movimento e se manifestam como distúrbios ionosféricos propagantes, isto é, como flutuações de natureza ondulatória na densidade do plasma ionosférico. Esses distúrbios podem ser detectados por meio de várias técnicas de rádio sondagem, mas atualmente as medições do conteúdo eletrônico total obtidas por meio de sinais de satélite são utilizadas com esta finalidade. Tendo em vista o exposto, o propósito do presente trabalho é desenvolver ferramentas computacionais munidas com as principais técnicas matemáticas, tais como análise wavelet e decomposição em modo empírico, para a identificação e caracterização de variações geomagnéticas e distúrbios ionosféricos propagantes causados tanto pela atividade solar quanto por terremotos tsunamigênicos. Além de seu propósito científico, este trabalho tem importância prática, pois a compreensão desses fenômenos pode ajudar no desenvolvimento de sistemas de previsão e alerta do Clima Espacial e de catástrofes, podendo evitar ou mitigar prejuízos econômicos e, principalmente, humanos.Item Exploring the centennial-scale climate history of Southern Brazil with Ocotea porosa (Nees & Mart.) Barroso Tree-Rings(MDPI) Muraja, Daniela Oliveira Silva; Klausner, Virginia; Prestes, Alan; Aakala, Tuomas; Macedo, Humberto Gimenes; Silva, Iuri Rojahn daThis article explores the dendrochronological potential of Ocotea porosa (Nees & Mart) Barroso (Imbuia) for reconstructing past climate conditions in the General Carneiro region, Southern Brazil, utilizing well-established dendroclimatic techniques. A total of 41 samples of Imbuia were subjected to dendroclimatic analysis to reconstruct precipitation and temperature patterns over the period from 1446 to 2011. Notably, we achieved the longest reconstructions of spring precipitation and temperature for the Brazilian southern region, spanning an impressive 566-year timeframe, by employing a mean chronology approach. To achieve our objectives, we conducted a Pearson’s correlation analysis between the mean chronology and the climatic time series, with a monthly temporal resolution employed for model calibration. Impressively, our findings reveal significant correlations with coefficients as high as |rx,P| = 0.32 for precipitation and |rx,T| = 0.45 for temperature during the spring season. Importantly, our climate reconstructions may elucidate a direct influence of the El Niño—South Oscillation phenomenon on precipitation and temperature patterns, which, in turn, are intricately linked to the natural growth patterns of the Imbuia trees. These results shed valuable light on the historical climate variability in the Southern Brazil region and provide insights into the climatic drivers affecting the growth dynamics of Ocotea porosa (Nees & Mart) Barroso.Item Freya: an educational MATLAB GUI-based tool for generalized Fourier series(Research, Society and Development) Macedo, Humberto Gimenes; Oliveira, Virgínia Klausner de; Gomes, Anna Karina Fontes; Fernandes, Francisco Carlos RochaThe Fourier analysis is a very powerful mathematical tool to decompose functions into their frequency components. Due to this, it has applications in a wide variety of fields inside the realm of science and engineering. As usual, this theory starts with a discussion about the trigonometric Fourier series, the expansion of a function in terms of sines and cosines, and then is generalized in the sense that other functions rather than the trigonometric ones can be used as an orthogonal basis, as the eigenfunctions of some specific Sturm-Liouville problems, such as Bessel functions and Legendre polynomials. In this direction, we present the so- called Freya, an educational graphical user interface (GUI) for the generalized Fourier series developed using the interactive MATLAB (MATrix Laboratory) App Designer environment. We aim to provide a user-friendly tool as a learning aid system for students to gain a comprehensive understanding of the subject as well as for teaching.Item Geomagnetic Disturbances During the Maule (2010) Tsunami Detected by Four Spatiotemporal Methods(Springer Nature Link) Klausner, Virginia; Macedo, Humberto Gimenes; Cezarini, Marina Vedelago; Ojeda-González, Arian; Prestes, Alan; Cândido, Claudia Maria Nicoli; Kherani, Esfhan Alam; Santos, Thiago de AlmeidaSeparating tsunamigenic variations in geomagnetic field measurements in the presence of more dominant magnetic variations by magnetospheric and ionospheric currents is a challenging task. The purpose of this article is to survey the tsunamigenic variations in the vertical component (Z) and the horizontal component (H) of the geomagnetic field using four spatiotemporal methods. Spatiotemporal analysis has shown enormous potential and efficiency in retrieving tsunamigenic contributions from geomagnetic field measurements. We select the Maule (2010) tsunami event on the west coast of Chile and examine the geomagnetic measurements from 13 ground magnetometers scattered in the Pacific Ocean covering a wide area from Chile, crossing the Pacific Ocean to Japan. The tsunamigenic magnetic disturbances are possibly due to two types of contributions, one arising from direct ocean motion and the other from atmospheric motion, both associated with tsunami forcing. Moreover, even though the tsunami waves decrease considerably with increasing epicentral distance, the tsunamigenic contributions are retrieved from a magnetic observatory in Australia ( 13,000 km radial distance from the epicenter). These results suggest that various types of tsunamigenic disturbances can be identified well from the integrated analysis framework presented in this work.Item Lithosphere atmosphere ionosphere coupling during the September 2015 Coquimbo earthquake(Springer Nature Link) Adhikari, Bhoj Raj; Klausner, Virgínia; Cândido, Claudia Maria Nicoli; Poudel, Prakash; Macedo, Humberto Gimenes; Silwal, Ashok; Gautam, Sujan Prasad; Calabia, Andrés; Shah, MunawarThis study explores temporal variations in seismic data, interplanetary parameters, and geomagnetic indices during the 2015 Coquimbo earthquake. We employ wavelet transform techniques to investigate potential coupling mechanisms between the lithosphere, atmosphere, and ionosphere (LAI), even during geomagnetically disturbed periods. Our analysis is strengthened by evaluating geomagnetic data and all- sky images within a 2000–3000 km radius of the epicenter. We explore the post-Chilean earthquake seismogenic perturbations in the upper atmosphere on September 16–17, 2015. Coseismic and post- seismic events emerge in the Brazilian region 1–3 hrs after the earthquake onset. The co-occurrence and subsequent response of these disturbances to seismic events suggest their seismogenic nature. Addi- tionally, we utilize geomagnetic storm and interplanetary magnetic Beld (IMF) indices to differentiate magnetic Cuctuations arising from solar storms during seismic events. While our study detects magnetic disturbances associated with seismic activity, distinguishing them from the eAects of solar storms in the geomagnetic records or all-sky images remains challenging. These observations prompt further investigation into the intricate interplay between geomagnetic and ionospheric disturbances and their connection to seismic and geomagnetic storm activity.Item Principal component analysis applied to dendrochronology(Universidade Federal do Rio Grande do Norte) Silva, Daniela Oliveira da; Klausner, Virginia; Prestes, Alan; Macedo, Humberto GimenesThis work uses samples of the species Ocotea porosa (Nees & Mart) Barroso (Imbuia), collected in the city of General Carneiro, Southeast region of the State of Paraná (26o24'01 25"S 51o24'03 91"W), Brazil, to generate average chronology (GC index) of this region. The objective of this article is to remove the natural growth trends of trees using a tool that is still little explored for this purpose, Principal Component Analysis (PCA). In each tree sample, the width of each growth ring was measured, obtaining a time series (1 ring per year). The samples were selected using Cluster Analysis, which classifies samples based on their similarities. Once the Principal Components (PCs) were obtained, the dendrochronological series were reconstructed without the first PC. This methodology is an estimate of the trend that best represents the natural growth of all trees on the site. The arithmetic mean of the series without the 1st PC is the GC index. It was found that PCA has three benefits: fast data processing, preservation of low-frequency signals and, when integrated with a powerful tool, the Alternated Least Squares (ALS) method, missing data estimation.