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9th International Congress of the Brazilian Geophysical Society
- Conference date: 11 Sep 2005 - 14 Sep 2005
- Location: Salvador, Bahia, Brazil
- Published: 11 September 2005
401 - 420 of 462 results
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Geomagnetically induced currents – GIC in electric power system at low latitudes in Brazil: A case study
Authors Nalin B. Trivedi Convênio, Santa Maria, Ícaro Vitorello, Wanderli Kabata, Severino L. G. Dutra, Antonio L. Padilha, Mauricio S. Bologna, Marcelo B. de Paula, Maria José F. Barbosa, São José dos Campos, Alexandre Pinhel Soares, Guilherme Sarcinelli Luz, Salvatore Mantuano Filho, Fabio de Abreu Pinto and José Antonio F. MendesGeomagnetically induced currents (GIC) are a ground end manifestation of space weather processes. During the large geomagnetic storms the GIC end up flowing between the ground points of the power transformers and the electric power transmission lines connecting the transformers. In the high latitude regions damages to the power transformers are reported where the range of the storm time geomagnetic variations is very large and hence the large GIC compared to the range of variations observed at low latitudes. However GIC damages to the power transformers are a complex process it needs careful evalution even at the low latitude regions in Brazil. We report here a first such study conducted under a cooperative project between FURNAS and INPE.
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Geomagnetic storm-time variations in the South Atlantic Anomaly Region
Geomagnetic variations in the horizontal components H (North-South) and D (East-West) during the large geomagnetic storm of 7 to 10 November 2004 are studied from the data collected at the stations São Martinho da Serra – SMS (29.43° S, 53.82° W and 33° dip) and Vassouras (22.40°S, 43.65° W and 33° dip). We have observed amplitude differences in the H variations and in the D variations between the two stations. The ring currents seem to undergo quick changes between the two stations situated in the South Atlantic Anomaly-SAMA region. The local time difference between the two stations is only 40 minutes.
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Análise do espectro temporal de ondas de gravidade por meio de keogramas
Authors F.A. Vargas, F. A., C.T.B. Kattab, C. T. B., C.G.M. Gobbi, D. Takahashi, H. Brum and C. G. M.O objetivo deste trabalho é o estudo do espectro observável da freqüência temporal de ondas de gravidade utilizando para tal os keogramas gerados a partir de imagens da emissão do OH da aeroluminescência. As imagens utilizadas foram obtidas em Cachoeira Paulista entre Junho de 2004 e março de 2005 por meio de um imageador CCD all-sky adquirido recentemente pelo grupo LUME do INPE. Através da análise dos keogramas, foi possível verificar que o espectro das ondas de gravidade comporta-se segundo uma lei de potência, apresentando um valor absoluto do índice espectral de 1,72 com desvio padrão de 0,04 para o conjunto de dados como um todo. Este valor concorda muito bem com dados experimentais de outras localidades, que mostram que o espectro de freqüência, em geral, apresenta índice espectral entre 1,66–2, calculado por medidas de diferentes instrumentos. Este estudo apresenta uma nova técnica de determinação do espectro em freqüência temporal utilizando imagens da aeroluminescência.
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Analysis of the Geomagnetic Storm Variations and the count-rate of Cosmic Ray Muons recorded at the Brazilian Southern Space Observatory
An analysis of geomagnetic storm variations and the count rate of cosmic ray muons recorded at the Brazilian Southern Space Observatory -OES/CRSPE/INPE-MCT, in São Martinho da Serra, RS during the month of November 2004, is presented in this paper. The geomagnetic measurements are done by a three component low noise fluxgate magnetometer and the count rate of cosmic ray muons, are recorded by a multidirectional muon detector, both instruments installed at the Observatory. The fluxgate magnetometer measures variations in the three orthogonal component of Earth magnetic field, H (Nort-South), D (East-West) and Z (Vertical), with data sampling rate of 0.5 Hz. The muon detector records hourly count rates. The arrival of a solar disturbance can be identify observing the decrease in the muon count rate. The goal of this work is to describe the physical morphology and phenomenology observed during the geomagnetic storm of November 2004, using the H component of the geomagnetic field and vertical channel V (Sun-Earth) of the multi-directional muon detector in South of Brazil.
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The solar origin of the October 21st-22nd (1999) very intense geomagnetic storm
In this work we address the solar origin of the October 21st -22nd (1999) very intense geomagnetic storm, which was caused by the interaction between an interplanetary ejecta (ICME) and a high speed stream. We believe that a high speed stream compressed the interplanetary ejecta and intensified its internal magnetic field, thus increasing the intensity of the geomagnetic storms. This kind of event is very difficult to predict based on remote observations of the solar corona, such as those from the Large Angle and Spectroscopic Coronagraph – LASCO, abord the Solar and Heliospheric Observatory – SOHO, because they are normaly related to relatively slow CMEs. Using combined data from different instruments, we present evidences on the solar disk of a coronal hole just beside (to the east) the active region from which the coronal mass ejection was liftted off. In the last solar cycle at least 1 out of 14 very intense geomangetic storms, i.e. peak Dst < -200 nT, was caused by such a mechanism.
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Ground-based observations of solar UV radiation at Tokyo, Brazil and Chile
Authors H. Nozawa, H. Yamamoto, K. Makita, N. J. Schuch, D. K. Pinheiro, S. Carbone, A. J. Foppiano and R. M. Mac-MahonIn this paper, we show some results of ground-based observations of solar ultraviolet (UV) radiations using UV radiometers and spectroradiometers. Our observations have been carried out at Ikebukuro, Japan and São Martinho, Brazil since 2002. Variation in flux ratio of UV-B to UV-A showed clear anti-correlation with that of effective ozone. As a result of functional fitting, exponential relations between the ratio and effective ozone were obtained. We are going to investigate long-term solar UV and ozone variations, not only using data taken at Japan and Brazil, but also at Chile.
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Ground Gamma Ray (GGR) activity associated with rain and lightning
Authors U. B. Jayanthi, A. A. Gusev, J.A.C.F. Neri, T. Villela, Pinto Jr., G. I. Pugacheva and K. C. TalaveraThe naturally occurring environmental Ground Gamma Radiation (GGR) is established as due to the radon progeny and efforts are continuously being made to detect the associated increases in GGR due to rain precipitation and lightning phenomena. We have installed, a Gamma radiation monitoring system with the detector equipment situated within a distance of 100 meters from two rocket launch towers for induced lightning. The detector, a NaI (Tl) crystal of 40 cm dia., is monitored on a continuous basis every 10 s in the energy range of 50 keV to ~ 1MeV. The precipitation rates, electrical field parameters etc., are available at the site. The system is in operation since February 2005, and has produced data during events corresponding to rain precipitation and lightning activity and the preliminary results will be presented.
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Observations of transient luminous events from space – a review
By Yoav YairWe review the results of space-based observations of Transient Luminous Events occurring in the mesosphere, occurring in conjunction with intense lightning flashes. The global rate of these events has significant implications on the global electrical circuit, combining the lower troposphere with the ionosphere. The needed TLE climatology can be best addressed by data from orbiting space platforms. The results from various such platforms are presented: from early space shuttle missions, the MEIDEX campaign, the LSO on-board the ISS and unmanned instruments on the ROCSAT-2 and RHESSI satellites. Future missions are briefly described.
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Resultados Preliminares de Estudo do Comportamento da Camada F Ionosférica sob o Equador Magnético a partir de Dados de Digissonda
The pre-reversal enhancement is a phenomenon of the evening equatorial ionosphere that has been pointed as decisive factor in the formation of the plasma bubbles of the F region. This enhancement can be observed through the data analysis of several equipments, among them: radars and digisondes. A digisonde 256 of INPE is installed and collecting data in São Luís (2.33° S, 44.2° W, dip: -0.5°). In the present work we have used the peak height of the F2 layer (hmF2) and the virtual height of the F layer (h'F) from some selected days in 2003 to study of speed of the layer F ascent in the equatorial zone during the pre-reversal period. The peak heights of the F2 layer obtained from the data analysis are compared with the same parameter obtained from simulations of electron density profiles. For the simulations we have used the
International Reference Ionosphere model - IRI. The speed of vertical drift is calculated from the data collected by the digisonde. The data set selected for this analysis covers some days from the periods around summer solstice and around autumn equinox in 2003. According the level of magnetic activity, the days of data acquisitions were classified between calm and disturbed. The results are presented and discussed in terms of the season and in terms of magnetic disturbance level.
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Análise do Ozônio Troposférico sobre o Observatório Espacial do Sul de 1996 a 2000
Dentro da Parceria entre o Laboratório de Ciências Espaciais de Santa Maria – LACESM/CT/UFSM e o Centro Regional Sul de Pesquisas Espaciais – CRSPE/INPE – MCT, sondagens atmosféricas para medida de perfis de ozônio troposférico e estratosférico tem sido desenvolvidas no Observatório Espacial do Sul (29,4°S, 53,8°W) desde 1996. Neste trabalho são analisadas 50 sondagens lançadas de novembro de 1996 a dezembro de 2000. Foram analisadas todas as sondagens que atingiram a altitude mínima de 17,5 km, a altitude da tropopausa sobre a região. A variação sazonal de ozônio troposférico no Observatório Espacial do Sul é ao redor de 55%. A média do ozônio troposférico no período é 31,3 ± 5,7 UD (máximo em outubro de 40,2 UD e mínimo em março de 22,9 UD). O ozônio troposférico representa aproximadamente 12% da coluna total de ozônio (9% em março e 15% em outubro). Cerca de 62 % das sondagens apresentaram picos secundários de ozônio na troposfera. A altitude média da presença dos picos está ao redor 3,3 km, mas houve ocorrência de picos numa faixa de 0,9 a 6,1 km. A média da pressão parcial de ozônio nesta extensão de altitude sem os picos é 19,5 ± 3,5 μhPa, enquanto que com os picos a média é de 38,8 ± 10,6 μhPa. A distribuição sazonal dos picos é desigual, ocorrendo principalmente em janeiro, novembro e dezembro, com 100%, 91% e 70% das sondagens mensais, respectivamente.
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ELF / VLF LIGHTNING NETWORK TO MONITOR CHARGE DISTRIBUTION AND CONTINUING CURRENT
More LessChanges of the vertical electric field due to individual strokes of multiple-stroke flashes to ground have been used to determinate sources of charge and the occurrence of continuous current in a thunderstorm cloud. This paper presents a technical description of the development and installation of a multiple station ELF/VLF electric field network to study the occurrence of continuing current in cloud-to-ground lightning flashes. Through the data recorded by the multiple stations ELF/VLF sensors the charge destroyed in the strokes and the signals related to continuing current in a region of about 1000 km*2 will be obtained. The data from the sensors network will be analyzed using the RINDAT (Integrated Lightning Detection Network) support. The network will be developed by the Atmospheric Electricity Group (ELAT) of the National Institute of Space Research (INPE). The Optical Ground Wires (OPGW) technology is used for data communications in power transmission lines. The studies using this network can also be used to a better understanding of the damages produced by lightning discharges on OPGW cable, providing information for simulation in laboratory of the continuing current effect on these cables.
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Mesosphere-Ionosphere coupling processes observed by ionosonde and airglow photometer in the equatorial region
Authors H. Takahashi, M A. Abdu, I. S. Batista, C. M. Wrasse, D. Gobbi, L. M. Lima and R. A. BuritiEquatorial ionosphere sounding at São Luís (2.6 S, 44.2 W) and Fortaleza (3.9 S, 38.4 W), and mesospheric airglow OI5577, O2b(0,1) and OH(6,2) emissions and OH rotational temperature observation at Cariri (7.4 S, 36.5 W) have been carried out since 1999. Spectral analyses of the ionospheric F-layer bottom height (h’F) and mesospheric airglow emission intensities reveal that there are quasi 2 and 4 day period oscillations in their temporal variations. Simultaneously observed meteor wind at 90 km of altitude at Cariri also showed similar periodic oscillations. It might indicate that planetary scale oscillations, Rossby-gravity waves and Ultra Fast Kelvin waves, are present in the ionosphere, passing through the mesosphere.
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Ionospheric foF2 anomalies during Halloween events: A preliminary Look
By R. P. KaneThe global evolutions of foF2 anomalies were examined for the very intense geomagnetic storms, namely the Halloween events of October-November 2003 (Event X, Oct. 29-30, 2003, Dst -401 nT; Event Y, Nov. 20-21, 2003, Dst -472 nT). For Event X (Oct. 29-30, 2003, slight winter in NH and summer in SH), troughs (negative storms) were clearly seen for ~65oN at nighttime, but not at any other LTs. Troughs were strongly seen in high southern latitudes, as if this was a summer storm for SH. For northern midlatitudes as also for low latitudes, there were very strong positive effects on Oct. 29, followed by negative effects next day. For Event Y (Nov. 20-21, 2003, winter in NH and summer in SH), there were no troughs in NH high latitudes for morning and evening hours but there were troughs for night. For midlatitudes and low latitudes, some longitudes showed strong negative effects in the early morning as expected, but some longitudes showed strong positive effects at noon and in the evening hours. A disconcerting feature was the presence of strong positive effects in the 24 hours before the storm commencement.
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Perturbações Gravitacionais e a Atividade Tectônica em Europa
More LessOrbital ressonance combined with gravity tides generated by Jupiter have a strong effect on the Europa’s thermal evolution and tectonic features observed at the surface of this satellite. With the energy supplied by dissipation of gravity perturbations, a process of convection was instaled on a possible subsurface ocean. This mechanism is responsible for the vast network of ridges in the Europa’s surface, and can be explained for the rheological properties of ice.
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Effects of High-Intensity Long-Duration Continuous AE Activity in the Equatorial Ionosphere Dynamics
The High Intensity Long-Duration Continuous AE Activity – HILDCAAs are continuous activity of high intensity auroral currents for days or weeks, in the absence of geomagnetic storms. The HILDCAAs effects on the low latitude ionosphere are not very well known since they have not been experimentally studied in detail. In this work we analyze the responses of the equatorial ionosphere over the Brazilian region to intense episodes of High Intensity Long-Duration Continuous AE Activity – HILDCAAs on the equatorial ionosphere in the Brazilian region during the periods of 27-31 March 2001 and 12-16 April 2004. The following experimental data were used here: 1. Ionospheric parameters h´F, hmF2 and foF2 obtained from ground-based either Digisonde or digital ionosonde located at São Luís (2,33S; 44,2W, dip 1.6S epoch 2001), Fortaleza (3o53´S 38o25´W dip 10.9S epoch 2001) and Cachoeira Paulista (22o41´S , 45o 00W, dip -31.8 epoch 2001).2. The auroral indexes AU, AL, and AE, and the Dst index, and 3. Interplanetary data from the Advanced Composition Explorer/ACE satellite orbiting around Lagrangian L1: north-south magnetic field component Bz, solar wind velocity VH, plasma temperature TH, and electric field.
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Analyses of magnetic storms effects on ionosphere electron content based on GPS data
More LessMagnetic storms can cause a lot of effects such as bright auroras visible at more southern latitudes than usual, or even to interfere with satellite communications; disrupting power grids; even short out orbiting satellites, rendering them permanently inoperable. Processing GPS data make possible to have a visualization of the Ionosphere behavior on days highly affected by the magnetic storms. The purpose of this paper is to show the effects of magnetic storms on the behavior of the Ionosphere electron content based on GPS data.
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Study of ionospheric irregularities during intense magnetic storms
Authors L. F. C. de Rezende, E. R. de Paula, Inez S. Batista, I. J. Kantor and M. T. H. MuellaThe effects of intense magnetic storms over ionospheric irregularities were analyzed using GPS data from the stations of São Luís (2.570 S, 44.210 W, dip latitude 1.730 S) in the equatorial region, São José dos Campos (23.070 S, 45.860 W, dip latitude 18.010 S) and Cachoeira Paulista (22.570 S, 45.070 W, dip latitude 18.120 S) both under the Equatorial Ionospheric Anomaly (EIA), and São Martinho da Serra (29.280 S, 53.820 W, dip latitude 18.570 S), located in the South of Brazil. Total Electron Content (TEC) data were also analyzed. The two storms analyzed occurred in October 28-31, 2003 and in November, 7-11, 2004. The Dst (Disturbance Storm-Time) index reached –401 nT around 23 UT in October 30 and –373 nT around 7 UT in November 8. In the night of 29/30 October, during the storm main phase, it was observed that TEC in São José dos Campos reached high values in comparison to a quiet magnetic day. Scintillation was strongest for Cachoeira Paulista (under EIA) and São Martinho da Serra, South of Brazil, compared to the quiet day (Oct 10). During the November 8 storm, TEC keeps the behavior of a quiet day except during days 10 and 11, when a large TEC decrease was observed. The scintillation was inhibited for the São Luís and São José dos Campos stations.
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Pororocas Mesosféricas Equatoriais
Authors J. Fechine, A.F. Medeiros, A. F., R.A. Buriti, R. A. Takahashi, C.M. Wrasse, C. M. and D. GobbiBaseado na observação de inúmeras pororocas mesosféricas em São João do Cariri, Brasil (7,4oS 36,5oO), foi realizada uma verificação das previsões do modelo de Dewan e Picard (1998, 2001). No presente trabalho foram utilizados dois anos de dados de um imageador all sky e um fotômetro que operam rotineiramente no Observatório de Luminescência Atmosférica da Paraíba observando as camadas de airglow OH, O2 e OI5577. Vários aspectos do modelo foram investigados, a saber: a ausência de sazonalidade e a alta atividade de ondas de gravidade registrada antes dos eventos, a direção preferencial de propagação e o horário de maior ocorrência do fenômeno, as primeiras observações de pororocas em formação e/ou dissipação e de pororocas não ondulares, uma estatística dos parâmetros físicos observados, as variações na intensidade de emissão e na temperatura rotacional das camadas de airglow em resposta à passagem das pororocas, o comportamento do ducto mesosférico e as suas implicações para os efeitos de complementaridade previstos e não previstos pelo modelo, e finalmente, saltos na intensidade de emissão simultâneos a diminuição na temperatura rotacional, que também não são previstos pelo modelo.
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Metodologia para a determinação da temperatura da mesosfera superior usando um Espectro-Imageador
More LessIn this work we’ll present a new methodology to calculate the temperature in the upper mesosphere. For this propose was determined the instrumental characteristics and was made the acquisition airglow data. The instrument consist of the imaging spectrometer that selected a wavelength range of the OH(6-2) airglow emission in interference cycles pattern which are show in image form. The airglow data was obtained at INPE observatory site located at Cachoeira Paulista(22.7°S, 45.0°W), Brazil. The application this methodology resulted temperature values that agree with temperature values observed in the upper mesosphere.
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Anysotropy of the Solar Variables Measured by SOHO Satellite
Authors M.J.A. Bolzan, M. J. A., P.C. Vieira and P. C.We studied the anisotropy in turbulent time-series of the solar wind velocity and proton density measured by SOHO satellite, during the two conditions of Solar acitivities, moderate (years 1996 and 1997) and high activities (years 1999 to 2004). An approach based in the correlation coefficient between of the great and small scales and Morlet Wavelet Transform are used. The results, explained in terms of memory effect, shown that the high activities of the Sun promote an increase of memory in both variables. Furthermore, an explanation in terms of Coherent Structure in the turbulent flows are presented.
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