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Submissões Recentes
Influence of Climate and Solar Variability on Growth Rings of Araucaria angustifolia in Três Barras National Forest (Brazil)
(MDPI) Muraja, Daniela Oliveira Silva; Klausner, Virginia; Prestes, Alan; Silva, Aline Conceicao da; Lemes, Cecilia Leite
This research applies continuous wavelet analysis and seasonal correlation anal- ysis to tree-ring data from Três Barras National Forest (FLONA Três Barras), revealing diverse influences on growth, including climate, solar activity, and external factors. The methodology involved tree-ring collection and subsequent wavelet and seasonal analy- ses to unveil the non-stationary characteristics of and multifaceted influences on growth. Key findings include the subtle effects of El Niño events on tree-ring development, the sensitivity of Araucaria angustifolia to temperature changes, the significant influence of precipitation during drought periods, and the intricate relationship between tree growth and solar cycles. The El Niño–Southern Oscillation (ENSO) emerges as a primary climatic driver during specific intervals, with external factors (precipitation, temperature, and solar cycle–solar irradiance) influencing tree response between 1936 and 1989. Additionally, the seasonal correlation analysis highlighted the importance of sub-annual climate variability, capturing specific intervals, such as a 3-month season ending in March of the previous year, that significantly impacted tree-ring growth. The study underscores the importance of protecting the endangered Araucaria angustifolia for climatic studies and local commu- nities. Historically, in Brazil, Araucaria angustifolia seeds played a vital role in sustaining indigenous populations, which in turn helped to disperse and propagate forests, creating anthropogenic landscapes that highlight the interconnected relationship between humans and the preservation of these forests.
Global ionospheric response to a G2 and a G3 geomagnetic storms of November 4 and 5 2023
(Elsevier) Agyei-Yeboah, Ebenezer; Fagundes, Paulo Roberto; Tardelli, Alexandre; Pillat, Valdir Gil; Vieira, Francisco; Bolzan, Mauricio José Alvez
Two successive geomagnetic storms of G2 and G3 intensities were observed on November 4, 2023, and November 5, 2023. The results presented in this study investigated the impacts of two geomagnetic storms during the main phases at equatorial, low-latitude, and EIA and beyond over west/east American, west/east African/European, and west/east Asian longitudinal sectors. This study was carried out using 30 GPS receivers, 30 magnetometers, and three ionosondes (East Brazilian sector). Positive storm effects were observed during the main phases of both the G2 (storm1) and G3 (storm2) storms, however the magnitude of the positive storm effects was greater during the G3 main phase than during the G2 main phase. The American sectors recorded the highest VTEC variations. Negative storm effects were mostly observed over the Asian sectors. Minimal changes in VTEC were observed in the Asian sectors during both main phases, except over DAEJ. The American sectors exhibited the strongest positive storm responses, followed by the African and Asian sectors, with VTEC enhancements being more pronounced during the G3 storm’s main phase compared G2 storm. Positive ionospheric effects extended to higher latitudes during the main phase of G3 storm especially in the American sectors, likely due to eastward prompt pen- etration electric fields (PPEF) uplifting the F-region to altitudes where lower recombination rates lead to VTEC enhancement. This PPEF effect varied with longitude and storm intensity, resulting in significant positive ionospheric responses in the American sector, par- ticularly during the G3 storm. Variations in the thermospheric O/N2 ratio further influenced the VTEC changes across all sectors. The EIA exhibited notable disturbances, particularly in the American sector. By contrast, EIA crest features were less distinct in the African sector, highlighting the longitudinal dependencies of PPEF effects on the EIA structure. The EIA features were more pronounced during the main phase of the first storm, whereas during the second, the crests appeared to merge into one structure extending beyond the typical crest regions. The foF2 obtained from ionogram also increased during the main phases in the American sector with no significant h’F variations. The DH showed marked depressions, particularly in the American and African sectors, with the G3 storm producing stronger DH depressions than the G2 storm. Similar longitudinal and latitudinal DH variations were observed across both events, with substantial decreases in DH over specific stations, such as ABG and JAI, in the West Asian sector.
Evidence of Unusually Strong Equatorial Ionization Anomaly at Three Local Time Sectors During the Mother's Day Geomagnetic Storm On 10-11 May 2024
(Advancing Earth and Space Sciences) Rout, Diptiranjan; Kumar, Ankit; Singh, Ram; Patra, Swadesh; Karan, Deepak K.; Chakraborty, Shibaji; Scipion, Danny; Chakrabarty, Dibyendu; Riccobono, Juanita
This study uses multiple ground and satellite‐based measurements to investigate the extreme ionospheric response to the Mother's Day storm on May 10–11, 2024. Prompt penetration electric field caused a significant enhancement in the ionospheric vertical drift (∼ 95 m/s) and the equatorial electrojet strength (∼275 nT) over Jicamarca. These extreme eastward electric field perturbations, along with the large meridional wind, significantly altered the F‐region plasma fountain at different local times. The afternoon equatorial ionization anomaly (EIA) not only sustained for an exceptionally long duration (∼ 12 hr) but also expanded spatially over time. The separation between the two peaks of EIA crests exceeded ∼48° and ∼70° in the morning and evening sectors, respectively. This study shows, for the first time, that unusually strong EIA can not only develop at different local times but can also sustain for long duration under favorable conditions, which has implications for space weather applications.
Effects of planetary wave oscillation on E-sporadic (Es) layers during the rare Antarctic sudden stratospheric warming of 2019
(Elsevier) Fontes, Pedro Alves; Muella, Marcio Tadeu de Assis Honorato; Resende, Laysa Cristina Araújo; Jesus, Rodolfo de; Fagundes, Paulo Roberto; Mitra, Gourav; Pillat, Valdir Gil; Batista, Paulo Prado; Buriti, Ricardo Arlen; Correia, Emília; Muka, Peter Taiwo
This study investigates the impact of the rare 2019 Antarctic Sudden Stratospheric Warming (SSW) event on the top frequency parameter (ftEs) of the sporadic E (Es) layers, using data from several ionosondes located at low and mid-latitudes across the Southern and Northern Hemispheres, including stations in the American, Oceanian, and Asian regions. The ionosonde data were also used to identify frequency anomalies in the Es layers during the event. Additionally, data from three meteor radars in South America were used to further analyze the impact of the SSW, focusing on key parameters such as tidal winds and Planetary Wave (PW) oscillations. The study found significant ftEs peaks exceeding 10 MHz, particularly at low-latitude stations, with values reaching up to 20 MHz. The presence of these atypical peaks in ftEs was related to PW activity, which intensified the electron densities in the Es layers. A wavelet analysis of the ftEs and neutral wind data revealed oscillations associated with PW and tidal interactions, with dominant periods of ∼2–8-days. These patterns were more pronounced in the Southern Hemisphere, indicating stronger PW-tide coupling compared to the Northern Hemisphere. In addition, this study shows that the non-linear interaction between the PW and the tides occurred globally, generating secondary oscillations of ∼2–8-days on the Es layer development for the three continents. These oscillations were observed in the zonal (U) and meridional (V) winds of the diurnal and semidiurnal tides (DT and ST) during the SSW event, demonstrating a coupling in the troposphere-stratosphere-lower atmosphere dynamics. The coupling between the stratosphere and lower thermosphere contributed to the observed anomalies, revealing the broader impacts of SSW events on Es layer behavior. This study provides an understanding of the impact of SSW on Es layers, using ionosonde data and wave oscillation analysis that could enhance data assimilation models for more accurate ionospheric prediction.
Equatorial Ionization anomaly disturbances (EIA) triggered by the May 2024 solar Coronal Mass Ejection (CME): The strongest geomagnetic superstorm in the last two decades
(Elsevier) Fagundes, Paulo Roberto; Pillat, Valdir Gil; Habarulema, John Bosco; Muella, Marcio Tadeu de Assis Honorato; Venkatesh, Kavutarapu; Abreu, Alessandro José de; Anoruo, Chukwuma Moses; Vieira, Francisco; Welyargis, Kibrom Hadush; Agyei-Yeboah, Ebenezer; Tardelli, Alexandre; Felix, Gabriela de Sousa; Picanço, Giorgio Arlan da Silva
Between May 10–15, 2024, a geomagnetic superstorm, the most intense in the past two decades, was recorded. This G5-level super- storm exhibited a Disturbance Storm Time (Dst) index of −412 nT and a Kp index of 9. The sudden storm commencement (SSC) occurred on May 10 at 17:05 UT, followed by the main phase from 18:00 UT on May 10 to 03:00 UT on May 11. The recovery phase lasted from 03:00 UT on May 11 until May 15. During this period, nine X-class solar flares were observed, indicating intense solar activ- ity. The superstorm led to significant ionospheric disturbances, which were analyzed using data from two ionosonde stations and GPS- TEC data from a network across the American sector, covering equatorial to low-mid latitude regions. A negative storm effect was observed in the equatorial region, while a positive ionospheric effect was observed in the low-mid latitudes during the main phase, accom- panied by the uplift of the F-layer to altitudes exceeding 1024 km, driven by storm induced prompt penetration electric fields. Addition- ally, a strong negative storm effect was recorded during the recovery phase on May 11 in daytime, probably due to O/N2 ratio changes.