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High variability of the ionosphere is connected to geomagnetic, solar, and neutral atmosphere wave activity. Results of scaling analysis of solar data (F10.7, SSN), geomagnetic indices (Dst, Kp, AE), and ionospheric critical frequencies (foF2) show similar structure of Kp, AE and foF2 at periods in the range from 4 to 32 days. Data structure depends on the location of ionospheric stations. Correlation coefficients between foF2 and geomagnetic and solar indices depend on length of time scale. We show that vertical coupling exists between neutral atmosphere activity and sporadic E layer area. This connection is located predominantly on periods corresponding to internal modes of planetary waves. Interplanetary magnetic field discontinuities (Coronal mass ejections, Magnetic clouds, Hight speed solar streams) affect strongly the ionosphere. Analysed events lead to lowering of foF2, increase in heights of the layer F2 and oscillations of hmF2 and foF2 on periods in the order of hours. Powered by TCPDF (www.tcpdf.org)

Orientador: João Francisco Galera Monico / Resumo: A tecnologia Global Navigation Satellite Systems (GNSS) tem sido amplamente utilizada em posicionamento, desde as aplicações cotidianas (acurácia métrica), até aplicações que requerem alta acurácia (poucos cm ou dm). Quando se pretende obter alta acurácia, diferentes técnicas devem ser aplicadas a fim de minimizar os efeitos que o sinal sofre desde sua transmissão, no satélite, até sua recepção. O sinal GNSS ao se propagar na atmosfera neutra (da superfície até 50 km), é afetado por gases hidrostáticos e vapor d’água. A variação desses constituintes atmosféricos causa uma refração no sinal que gera um atraso. Esse atraso pode ocasionar erros na medida de no mínimo 2,5 m (zenital) e superior a 25 m (inclinado). A determinação do atraso na direção inclinada (satélite-receptor) de acordo com o ângulo de elevação é realizada pelas funções de mapeamento. Uma das técnicas para o cálculo do atraso é o traçado de raio (ray tracing). Essa técnica permite mapear o caminho real que o sinal percorreu e modelar a interferência da atmosfera neutra sobre esse sinal. Diferentes abordagens podem ser usadas para obter informações que descrevem os constituintes da atmosfera neutra. Dentre as possibilidades pode-se citar o uso de medidas de radiossondas, modelos de previsão do tempo e clima (PNT), medidas GNSS, assim como modelos teóricos. Modelos de PNT regionais do Centro de Previsão de Tempo e Estudos Climáticos (CPTEC) do Instituto Nacional de Pesquisas Espaciais (INPE) apresentam-se como um... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Global Navigation Satellite Systems (GNSS) technology has been widely used in positioning, from day-to-day applications (metric accuracy) to applications that require high accuracy (few cm or dm). For high accuracy, different techniques may be applied to minimize the effects that the signal suffers from its transmission on the satellite to its reception. GNSS signal when propagating in the neutral atmosphere (from surface up to 50km) is influenced by hydrostatic gases and water vapor. The variation of these atmospheric constituents causes a refraction in the signal that generates a delay. This delay may cause errors of at least 2.5 m (zenith) and greater than 25 m (slant). The determination of the delay in the slanted direction (satellite-receiver) according to the elevation angle is performed by the mapping functions. One of the techniques for calculating the delay is raytracing. This technique allows us to map the actual path that the signal has traveled and to model the interference of the neutral atmosphere on it. Different approaches can be used to obtain information describing the neutral atmosphere constituents - temperature, pressure and humidity. The possibilities include the use of radiosonde measurements, weather and climate models (NWP), GNSS measurements, as well as theoretical models. Regional NWP models from the Center Weather Forecasting and Climate Studies (CPTEC) of the National Institute for Space Research (INPE) are a good alternative to provide atmospheri... (Complete abstract click electronic access below) / Doutor