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Item Exploring patterns in dendrochronological data through cluster analysis(Universidade Federal do Paraná) Muraja, Daniela Oliveira Silva; Leite, Cecília Lemes; Klausner, Virginia; Prestes, Alan; Silva, Iuri Rojahn daThis study employed the dendrogram methodology to analyze time series data obtained from measuring tree growth rings. A total of 64 samples were collected from 21 individual trees. Polynomials were applied to filter the natural growth pattern of the trees and enhance the impact of external factors, such as climate influences. Cluster analysis using Ward's minimum variance and Euclidean squared distance was utilized to group the data based on similarity. Three dendrograms were constructed, consisting of 10, 47, and 64 samples, respectively. The analysis revealed that the samples with the highest correlations, encompassing over 95% of the total samples, formed homogeneous groups. Pearson correlation was also employed to confirm the results obtained from the dendrograms. Consequently, it can be affirmed that the most suitable samples were utilized in constructing the average chronology from the available data.Item Enhancing learning of the Grad-Shafranov Equation through scientific literature: part 1 of a physics education series(Sociedade Brasileira de Física) Ojeda González, Arian; Santos, Lenadro Nunes dos; La Luz, Victor Hugo de; Oliveira, Matheus Felipe Cristaldo de; Sousa, Antonio Nilson Laurindo; Prestes, Alan; Klausner, Virgínia; Pilling, SergioThis article provides a comprehensive review of relevant studies in the fields of plasma physics, electromagnetism, and space physics. The aim is to demonstrate how the study of the scientific literature can be used to enhance problem-solving abilities and develop innovative solutions in physics. In this paper, we focus on the study of solutions of the specific Grad-Shafranov equation. Two of the new solutions proposed by Yoon and Lui (2005) are used as a basis for the development of a new solution. The new solution presented has singular points similar to the Yoon-Lui-2 solution, but with an inverted configuration, and also presents less rounded double islands compared to the Yoon-Lui-2 solution. Additionally, the new solution does not exhibit the formation of a current ring, a characteristic of the Yoon-Lui-1 solution, and varying its parameters may lead to higher plasma confinement efficiency. In summary, we illustrate how a thorough analysis of literature can serve as a powerful means for generating innovative approaches to resolving theoretical issues in physics.Item Enhancing learning of the Grad-Shafranov equation through scientific literature: part 2 of a physics education series(Sociedade Brasileira de Física) Santos, Lenadro Nunes dos; Ojeda González, Arian; La Luz, Victor Hugo de; Oliveira, Virgínia Klausner de; Pilling, Sergio; Prestes, Alan; Sousa, Antonio Nilson Laurindo; Oliveira, Matheus Felipe Cristaldo deIn part 1 of our physics education series, we introduced a novel solution based on Yoon-Lui’s solutions 1 and 2. Building upon that, this follow-up presents a new solution obtained by combining the generating functions of Yoon-Lui-1 and Yoon-Lui-3, resulting in a new and simplified general solution. We also calculate the singular points and determine their coordinates for various parameter values. A graphical representation of the solution is presented, showing the magnetic field lines and current density distribution. The behavior of the magnetic field and the effect of varying the parameter are discussed. The observed magnetic islands and singular points are relevant in the fields of Plasma Physics and Space Physics, providing insights into magnetic structures in plasmas and their impact on confinement and stability. Furthermore, this study encourages innovation and equips researchers and students with the necessary tools to make meaningful contributions to the field, emphasizing the integration of scientific literature into physics education to promote a comprehensive understanding of physical concepts and their practical applications.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 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.Item Principal component analysis in the modeling of HILDCAAs during the Solar Minimum of Cycle 23/24(Elsevier) Klausner, Virginia; Lamin, Isabelle Cristine Pellegrini; Ojeda-González, Arian; Macedo, Humberto Gimenes; Cândido, Claudia Maria Nicoli; Prestes, Alan; Cezarini, Marina VedelagoIn this article, we propose a new approach to model the high-intensity, long-duration, continuous AE (Auroral Electrojet) activity (HILDCAA) by relaxing one of the criteria originally designed, based on the interplanetary features during the unusual Solar Minimum of Cycle 23/24 (SMC23/24). This relaxation does not intend to suppress or modify the original HILDCAAs’ conception, but propose a new view of the same phenomena by enlarging the sample of events, which in turn may improve space weather monitoring and prediction programs. To assess and classify the Alfvénity associated with HILDCAAs, the values of 4h-Windowed Pearson Cross-Correlation (4WPCC) between the IMF components and the solar wind speed components observed in situ at the Lagrangian point L1 (1 AU) were evaluated. The principal component analysis (PCA) was performed on the dataset and, from the first three principal components, which represent 65% of the accumulative percent variance, we applied principal component regression (PCR) in each of the following parameters: the AE index, the Interplanetary Magnetic Field (IMF) components, the plasma density, the solar wind speed, the temperature, the IMF magnitude, and the SYM-H geomagnetic index. Furthermore, we applied Multiple Linear Regression (MLR) to establish a linear model to express the AE index in terms of the PCR-based model parameters. The AE MLR-based model demonstrated to hold a prognosis potential for HILDCAAs. Despite that, this model is only suitable for the SMC23/24. In this sense, this model might be implemented a real-time analysis for short-term HILDCAA prognosis in the near future.Item Principal Components Analysis: An Alternative Way for Removing Natural Growth Trends(Springer Nature Link) Silva, Daniela Oliveira da; Klausner, Virginia; Prestes, Alan; Macedo, Humberto Gimenes; Aakala, Tuomas; Silva, Iuri Rojahn daIn this article, we establish a new approach for removing natural growth trends from tree-ring samples, also called detrending. We demonstrate this approach using Ocotea porosa (Nees & Mart) Barroso trees. Nondestructive samples were collected in General Carneiro city, located in the Brazilian southern region (Paraná state). To remove natural tree growth trends, principal components analysis (PCA) was applied on the tree-ring series as a new detrending method. From this, we obtained the tree-ring indices by reconstructing the tree-ring series without the first principal component (PC), which we expect to represent the natural growth trend. The performance of this PCA method was then compared to other detrending methods commonly used in dendrochronology, such as the cubic spline method, negative exponential or linear regression curve, and the regional curve standardization method. A comparison of these methods showed that the PCA detrending method can be used as an alternative to traditional methods since (1) it preserves the low-frequency variance in the 566-year chronology and (2) represents an automatic way to remove the natural growth trends of all individual measurement series at the same time. Moreover, when implemented using the alternating least squares (ALS) method, the PCA can deal with tree-ring series of different lengths.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 Ocean–atmosphere interaction identified in tree-ring time series from southern Brazil using cross-wavelet analysis(Springer Nature Link) Muraja, Daniela Oliveira Silva; Klausner, Virginia; Prestes, Alan; Silva, Iuri Rojahn daTropical dendrochronology has gained significant attention in recent years, particularly with the dendrochronological study of new species that produce annual growth rings and are responsive to environmental changes. Despite the progress, the extent to which ocean–atmosphere interactions influence regional climate and, consequently, tree growth, is not fully understood. Among the new species, Ocotea porosa (Nees & Mart.) Barroso (also known as Imbuia) has shown excellent potential for climate research. This study investigates the climatic and solar influences on a chronology of 41 Imbuia tree samples. Pearson’s correlation was used alongside Wavelet transform to evaluate periodicities between the tree-ring chronology and climatic parameters such as the southern-oscillation index (SOI), annual precipitation, El Niño 3.4 (PACE), and the South Atlantic Index (ATLS). Our analysis revealed evidence of the influence of the El Niño Southern Oscillation (SOI) on rainfall variability in the region, the Hale and Gleissberg solar cycles causing precipitation variation, likely due to the influence of the Atlantic Ocean, and the Brückner-Egeson-Lockyer climatic cycle, which is correlated with sunspot activity. Furthermore, our wavelet analysis identified possible connections to the Eastern Pacific-type El Niño events during five specific periods: 1911–1912, 1918–1919, 1976–1977, 1982–1983, and 1986–1987. The results indicate that southern Brazil is affected by several climatic and geophysical parameters from both the Atlantic and Pacific oceans, which directly affect the growth of Imbuia trees as their tree-ring series display sensitivity to these parameters.Item Análise de componentes principais aplicada à dendrocronologiaSilva, Daniela Oliveira da; Oliveira, Virgínia Klausner de; Prestes, Alan; Macedo, Humberto Gimenes