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- DissertaçãoAnálise de variações na radiação gama natural associada ao radônio e influência do campo elétrico atmosférico e efeitos meteorológicosOliveira, Rafael Ricardo Rosa de (2020-08-17)
Escola de Engenharia Mackenzie (EE)
Natural Gamma radiation is mainly produced during the interaction of energetic cosmic rays in the Earth’s atmosphere, the decay of radionucleides from the soil and transient energetic atmospheric phenomena. The variability of natural gama radiation and its relation to the atmospheric electric field is important for a better understanding of phenomena like thunderstorms and lightning. In this thesis, it is analyzed the natural gamma ray radiation for different meteorological conditions and verify its relation with the atmospheric electric field. The comparison is done for fair weather conditions on different timescale: annual, seasonal and monthly variations. During disturbed weather conditions it is reported and discussed events of abnormal and impulsive natural gamma radiation. The data were extracted from the El Leoncito Observatory in Argentina from April, 2018 to February, 2019. In fair weather averages, it was possible to obtain a good correlation between the local atmospheric electric field curve and the global electric field curve (Carnegie curve) with a correlation coefficient of R = 0.94. In the curves of natural gamma radiation, a pattern was strongly dependent on the levels of atmospheric turbulence, with maximum radiation occurring close to sunrise and minimum occurring close to sunset. On days when there were abnormal variations in natural gamma radiation, meteorological conditions were analyzed and all events are generally preceded by thunderstorms and may also be accompanied by precipitation - DissertaçãoAnálise do campo elétrico atmosférico durante tempo bom e distúrbios geofísicosAnaya, José Carlos Tacza (2015-01-19)
Engenharia
In this dissertation, we present the capability of a new network of sensors to monitor the atmospheric electric field at various locations in South America. The main goal is to obtain the characteristic Universal Time daily curve of the atmospheric electric field in fair-weather. That curve is known as the Carnegie curve, which is related to the currents flowing in the Global Atmospheric Electric Circuit. This has been accomplished using monthly, seasonal and annual averages. After obtaining our standard curve of variation of the electric field in fair-weather, the deviations related to phenomena such as solar flares, solar protons events, geomagnetic storms, total solar eclipse and seismic activity are analyzed and commented. - DissertaçãoContribuição ao estudo de distúrbios ionosféricos utilizando a técnica de VLFCruz, Edith Liliana Macotela (2015-03-09)
Engenharia
The Earth-Low ionosphere system behaves as a waveguide for the propagation of radio waves of very low frequency (VLF). If in this system the electrical conductivity of its boundaries is perturbed, the propagation of the VLF waves will also be perturbed. There is a diversity of transient physical phenomena that are able to alter significantly the electrical conductivity of the lower ionosphere. The disturbance in this region is able to produce phase and amplitude variations with respect to a quiescent level of these waves. The aim of the present work is to study the response of the lower ionosphere to phenomena originated in the Earth, our solar system or even much farther away. For this purpose, VLF data obtained by SAVNET (South American VLF Network) during the solar cycle 24 was used. It was found that the correction by both the length of the path illuminated by the flare and the reference height coefficient allows normalizing the effect of ionospheric disturbances observed in the VLF phase signals that propagated along trajectories with a north-south or west-east direction, separately. The lower limit of detection for disturbances caused by the X-ray radiation excess is 1.8×10−9 Jm-2 and 2.6×10−7 Jm-2 for the nighttime and daytime lower ionosphere, respectively. Changes in the periodicities of the VLF signal, in the infrasonic band, were observed between 6 and 14 days prior to the seismic events, of magnitude 7, occurred in Haiti in 2010 and in Peru in 2011. Increases in the periodicities of the order of few minutes were observed when the shadow of the total solar eclipse of 2010 was moving on the Earth. Due to the solar eclipse the ionospheric reference height increased in ~3 km and the electron density decreased in 60 % of its quiescent level. Finally, it was found that the effective recombination coefficient, for 80 km height, was 1.1×10−5 cm-3s-1 during the time of the eclipse, which is an intermediate value between the diurnal and nocturnal conditions. - DissertaçãoDeterminação da opacidade atmosférica em comprimentos de ondas submilimétricasEspinoza, Deysi Veronica Cornejo (2017-07-28)
Escola de Engenharia Mackenzie (EE)
To understand the nature of the solar explosive radiation mechanisms at high frequency radio waves, which depends on the interpretation of the flux density spectrum (S), it is necessary to have a good estimate of the accuracy of S . For this reason, the atmospheric opacity determination is essential, to correct the observed solar radiation flux from radio telescopes in the ground. For high frequencies (e.g. in the sub-millimeter and infrared wavelength), the water vapor is mainly responsible of the atmospheric opacity. Thus, the solar radiation collected by the radio telescope can be strongly attenuated up to a factor of 1000 (e.g. at 405 GHz). Therefore, it is necessary to have a reliable estimate of the atmospheric opacity. The main aim of this work is to determine the atmospheric opacity at 212 and 405 GHz using the solar brightness method. Comparing with the characteristics of other methods in the literature, we find that this one allows to determine the atmospheric opacity up to considerably high values, and only depends on one parameter. Namely, the product 𝑃 = 𝜂𝑇, where 𝑇 is the brightness temperature of the Sun measured at 212 and 405 GHz and 𝜂 is the beam efficiency; we assume that the 𝑃 value is constant even though 𝑇 and 𝜂 are not well known individually. For the development of the present work, we were used approximately 18 thousand solar scans recorded by the Submillimetric Solar Telescope (SST, CASLEO, 2552 m altitude), for the period between 2002 and 2015, where only clear days with low opacity were considered. Using the solar brightness method, the 𝑃 value was calculated at 212 and 405 GHz. For the four beam at 212 GHz, we obtained: ¯ 𝑃 = 2446 ± 149 K (beam 1); ¯ 𝑃 = 2489±184 K (beam 2); ¯ 𝑃 = 2541±223 K (beam 3); ¯ 𝑃 = 2361±199 K (beam 4) and for the two beams at 405 GHz we obtained: ¯ 𝑃 = 3241±331 K (beam 5) and ¯ 𝑃 = 3299 ± 276 K (beam 6). Using the mean values ¯ 𝑃, the atmospheric opacities 𝜏212 and 𝜏405 were determined at 212 and 405 GHz, respectively. The correlation between the opacities 𝜏212 and 𝜏405, show that the opacity at 405 GHz ∼ 7 times more than that at 212 GHz. In addition, we also find that the atmospheric opacities determined with the method proposed in this work show an excellent correlation with the water vapor content, when this is measured simultaneously. - DissertaçãoEstudo em múltiplas frequências da baixa atmosfera solar durante explosõesHuaman, Denis Pavel Cabezas (2015-03-26)
Engenharia
O trabalho tem como objetivo estudar as perturbações da baixa atmosfera solar produzidas pelas explosões solares, usando observações em Hα, 30 THz (10 μm), UV/EUV, raios X e uma ampla faixa de emissões em ondas de rádio (microondas, milimétrica, submilimétrica); com o propósito de determinar a natureza dos processos físicos envolvidos. Este conjunto de dados multiespectrais nos permitiu (i) analisar os diferentes aspectos das explosões tanto na fase impulsiva como gradual, (ii) determinar a origem da emissão em rádio durante a fase gradual, e consequentemente (iii) entender melhor os mecanismos de aceleração das partículas. Os dados em Hα e 30 THz foram fornecidos pelo sistema de aquisição de dados com alta resolução temporal, instalado nos observatórios OSM1 e CASLEO2, adicionalmente dados do telescópio HASTA (H-Alpha Solar Telescope for Argentina) instalado no observatório OAFA3. Enquanto as observações em rádio, os dados foram do rádio polarímetro POEMAS (POlarization Emission of Millimeter Activity at the Sun) nas frequências de 45 e 90 GHz, do telescópio SST (Sub-millimeter Solar Telescope) nas frequências 212 e 405 GHz, ambos instalados no CASLEO. Dados na faixa de microondas (0,2-15 GHz) obtidos pela rede RSTN (Radio Solar Telescope Network). Além disso, foram considerados observações do Sol obtidas pelos satélites RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager), Fermi e GOES (Geostationary Operational Environmental Satellite) para raios X, e dos instrumentos AIA (Atmospheric Imaging Assembly), HMI (Helioseismic and Magnetic Imager), a bordo do satélite SDO (Solar Dynamics Observatory), respectivamente. - DissertaçãoVariabilidade das tempestades elétricas e sua relação com o campo elétrico atmosférico de tempo bom utilizando a rede WWLLNCcopa, Josue Gabriel Anca (2021-08-08)
Centro de Rádio Astronomia e Astrofísica Mackenzie (CRAAM)
Estudos realizados no século XX pelo navio do Instituto Carnegie de Washing ton mostraram que a variação média diária do campo elétrico atmosférico de tempo bom, conhecida também como curva de Carnegie, era independente do local de medição. A curva de Carnegie apresenta três máximos às 08, 14 e 19 UT, os quais correspondem aos horários locais de máxima atividade de tempestades elétricas na Ásia-Austrália, Europa-África e América respectivamente. Assim, as tempestades elétricas foram propostas como um dos principais geradores de corrente elétrica dentro do circuito elétrico atmosférico global (CEAG). Neste trabalho, analisamos dados da World Wide Lightning Location Network (WWLLN) para os anos 2012 e 2013, que nos fornece o tempo de ocorrência e a posição dos relâmpagos detecta dos de forma global. Nossa metodologia consiste em agrupar os dados de raios da WWLLN em uma matriz de densidade com uma resolução espacial de 0,1°x 0,1° (1 pixel) e uma resolução temporal de uma hora. O algoritmo utilizado identifica os pixels com relâmpagos e agrupa esses pixels com os pixels adjacentes para for mar a tempestade. Desta forma, foram geradas curvas diurnas (mensais, sazonais e anuais) de tempestades elétricas. As curvas obtidas foram comparadas com a curva de Carnegie (curva padrão), e com a curva de Vostok (medições mais recen tes) para entender a relação entre as variações do campo elétrico de tempo bom e as variações das tempestades elétricas. Nossos resultados mostram uma alta correla ção linear entre a ocorrência anual de tempestades elétricas diurnas e as curvas de Carnegie (R= 0,97) e Vostok (R = 0,98). Nos resultados sazonais encontrámos uma maior correlação nos meses de setembro-outubro-novembro (R = 0,98 e R = 0,99) e uma baixa correlação em junho-julho-agosto (R = 0,75 e R = 0,88) entre tempestades - Carnegie e tempestades - Vostok, respectivamente. Obtivemos uma média global de 841 tempestades por hora, que cobrem aproximadamente 0,132% da superfície terrestre e geram uma corrente total de 1120 A a cada momento. Essa corrente ge rada é descarregada na superfície terrestre em regiões de tempo bom, com uma densidade média de 2,2 pA/m2 e campo elétrico médio de 146,7 V/m.