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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 - 462 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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Very low frequency phase advances during solar X-ray flares
Authors Alessandra Abe Pacini, Jean-Pierre Raulin, Emília Correia and Pierre KaufmannVery Low Frequency (VLF) waves propagate in the Earth-ionosphere waveguide bounded by the base of the D-region and by the ground. VLF waves are very sensitive to the electron density profile in the D region, and they can propagate over long distances keeping a high stability for the observed phase and amplitude parameters. For these reasons VLF waves provide a useful diagnostic of the low ionosphere, in terms of its parameters β (conductivity sharpness) and H (reflection height). This study reports on Sudden Phase Anomalies (SPA) of VLF waves received at Atibaia (São Paulo, Brazil) and at Inubo (Japan), from several long distance (over 2800 kilometers) paths during solar flares. The time coverage of the data sample includes periods of high solar activity (January-March 1991 and October-December 1991) as well as epochs of reduced solar activity (January 1994 - July 1997). This report allows us to investigate the detect ability of X-ray producing ionization excess in the low ionosphere, and how this situation is modified along the solar cycle. The results are also discussed in terms of solar flare properties like intensity and spectrum. In particular during solar minimum, we were able to identify a lower X-ray flux level needed to account for a SPA (~ 5.10-7 and 4.10-8 Wm-2 in the 1-8 Ǻ and 0.5-4 Ǻ energy ranges respectively). We also confirm the importance of the X-ray spectral characteristics for the properties of the observed SPAs.
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EQUARS - Satélite Científico para Monitoramento da Atmosfera Equatorial
The objective of the EQUatorial Atmosphere Research Satellite (EQUARS), designed by, and presently under development, at INPE is the monitoring of the Earth’s equatorial low, middle, upper atmosphere and ionosphere. This work presents the project, design and development of the EQUARS onboard platform systems. Various aspects of the onboard subsystems, such as mechanical structure, thermal control, power supply, onboard computer, attitude control, data communication, and their importance to the mission accomplishment will be discussed.
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Relationships Between Intense Magnetic Storms Caused By Sheath Regions, CIRs and ICMEs
Authors A. de Lucas, E. Echer, W.D. Gonzalez, L.E.A. Vieira, L.F. Guarnieri, A. Dal Lago, M.R. da Silva and J.C. dos SantosIn this work we study comparatively intense magnetic storms (Dst < -100 nT) caused by Corotating Interaction Regions (CIRs), or by interplanetary coronal mass ejection (ICMEs), or by sheath regions. Our aim is to analyze their interplanetary characteristics (electric field Ey, Bs interplanetary magnetic field) and their energy coupling function, (e ), and the total energy input, (We ), to analyze the differences between events caused by different interplanetary structures. The geomagnetic data/indices are also employed to study the ring current dynamics and to search for the differences in the storm evolution in these events. The selected storms are 10 March 1998, 6 August 1998, 17 April 1999, 22 September 1999, 24 May 2000, and 6 de November 2000. The interplanetary data were obtained from ACE spacecraft’s Web page, and the geomagnetic data is from World Data Center for Geomagnetism - Kyoto (WDC-Kyoto) and from Space Physics Interactive Data Resource, on the NOAA’s web page.
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Um estudo sobre es ondas de choque no meio interplanetário
More LessO meio interplanetário, o espaço entre os planetas e o Sol, está permeado pelo vento solar que é a própria atmosfera solar se expandindo no espaço interplanetário. Esta atmosfera é composta por um plasma tênue magnetizado o qual favorece a ação das forças Coulombianas de longo alcance. Estas pela presença deste campo magnético, conseguem exercer seu papel que é o de transferência de momentum e informação às partículas provenientes do Sol. Qualquer mudança na atividade solar se reflete no meio interplanetário devido a transferência de informações. A agitação do Sol, conseqüência de sua constante atividade, é transmitida ao vento solar e freqüentemente produz Ondas de Choque. É possível, com o estudo das variações dos parâmetros interplanetários como: densidade, temperatura e velocidade do vento solar e intensidade do campo magnético interplanetário – CMI, identificar a presença desses choques e calcular sua velocidade, intensidade e direção. Neste trabalho utilizamos dados de plasma e CMI fornecidos pelo sistema de dados On-line da sonda ACE – Advanced Composition Explorer, para fazer um estudo acerca de ondas de choque, analisando os gráficos de dados destes eventos e classificando-os, segundo os perfis dos choques feitos por E. Echer et al. [2003], em choques frontais, rápidos e lentos; ou reversos, rápidos e lentos. Este estudo deteve-se ao período de 2002 – 2003, que corresponde ao declínio do
Ciclo Solar 23.
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GPS scintillations, TEC and zonal plasma drifts observed during the COPEX 2002 campaign: Preliminary results
Radio signal amplitude scintillations at the Global Positioning System (GPS) L1 frequency (1.575 GHz) and the ionospheric irregularity zonal velocities were measured simultaneously at three sites during the Conjugate Point Equatorial Experiment (COPEX)
campaign conducted in Brazil from October 1 to December 10, 2002. These observations used two GPS receivers at each site spaced geomagnetically in the eastwest direction and the three observation sites were located along a same magnetic meridian, one at the magnetic equator, Cachimbo (9.5º S, 54.8º W, dip angle: -3.9º), one at the northern conjugate point, Boa Vista (2.8º N, 60.7º W, dip angle: 22.5º) and one at the southern conjugate point, Campo Grande (20.5º S, 54.7º W, dip angle: -22.5º). The data collected in the COPEX campaign occurred during high scintillation activity months which are associated to periods of high occurrence of ionospheric plasma depletions, also known as plasma bubbles. The average decimetric solar radio flux for this period of increased solar activity was about 156. Only magnetically quiet days with åKp £ 24 were selected for this study. Simultaneous dual-frequency GPS receivers measurements revealed total electron content (TEC) decreases, which are bubble signatures, during the observed strong amplitude scintillations. In this paper we will present some preliminary investigations of latitudinal variations and dynamics of scintillations, TEC and ionospheric zonal plasma drifts over magnetic conjugate points.
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Upper atmosphere phenomena in Brazilian geomagnetic anomaly region and its surrounding area
Authors Kazuo Makita, Masanori Nishino, Tatuo Torii, Recardo Monreal, Albert Foppiano and J. SchuchIn order to examine the effect of high energy particle precipitation in Brazilian geomagnetic anomaly region, we examined optical phenomena obtained at Brazil and Japan. During large magnetic storm, airglow phenomena with multiple bands structure were observed at Brazil, however, remarkable airglow phenomena was not recognized at Okinawa. We also examined atmospheric electric field, cosmic ray and 38.2MHz emission during this magnetic storm period. Electric field enhancements were continuously observed for more than 27 hours during the recovery phase of magnetic storm and a good relationship was seen between electric field and 38.2MHz variations. However cosmic ray enhancement was not recognized during this period. On the other hand, we installed imaging riometer at SSO, Brazil
and recently Punta Arenas and Concepcion, Chile. At the present, we did not obtained simultaneous data at these 3 points. So, we shows the preliminary results of imaging riometer observations.
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Study of the gravity wave propagation direction observed by airglow imaging in the South American sector
Airglow all sky imaging observation has been carried out in three different locations in the south America, at Cachoeira Paulista (22.7 S, 45.0 W) in 1999, São João do Cariri (7.5 S, 36.5 W) in 2001 and Boa Vista (2.8 N, 60.7 W) in 2002. Comparing the atmospheric gravity wave characteristics retrieved from the image data for the three different sites and including a previous work at Alcantara (2.3 S, 44.5 W) carried out by Taylor et al. (1997), we found that there is a preferential propagation direction, from the Continent to Atlantic Ocean. Possible source of the wave generation is discussed.
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Spectral features of F-region plasma irregularities as observed by rocket- borne electron density probes from Brazil
Authors P. Muralikrishna and L.P. Vieira and M.A. AbduThe height variation of the ionospheric electron density was measured with rocket-borne electron density probes from Alcantara (2.31oS; 35.2oW) in Brazil. A Black Brant X sounding rocket was launched on 14-th October 1994 at 1955hrs (LT) to investigate the phenomenon of high-altitude equatorial spread-F events. Ground equipments were operated during the campaign to ensure that the rocket was launched under conditions favorable for the generation of plasma bubbles in the F-region. The electron density was measured by three different types of probes. A High Frequency Capacitance probe (HFC) gave density data with low height resolution, while a conventional Langmuir Probe (LP) and a Plasma Frequency Probe (PFP) measured the electron density and the spatial fluctuations in it. The k-spectra of the plasma irregularities were obtained by the spectral analysis of the electron density fluctuation data. An important feature observed was the continuous presence of plasma irregularities of a large range of vertical scale sizes in the altitude range of 340km to 817km. The electron number density varied considerably in these spatial structures, for example a decrease by a factor of 2.6 in a vertical extension of 1km near the altitude of 497km. Near 535km altitude the electron density increased by a factor of 1.8 within a height range of 2.7km. Density structures of vertical scale sizes in the range of hundreds of meters also were observed superposed on the large scale structures. During the rocket upleg two height regions of intense irregularities were observed, one between 366 and 480km and the other between 684 and 812km. The Langmuir Probe (LP) could make measurements of irregularities of vertical scale sizes more than 8m in these height ranges, while the Plasma Frequency Probe, could make measurements of irregularities of vertical scale sizes as small as 0.5m. Spectral features of these irregularities as observed by the two plasma probes at different height regions are presented and discussed here.
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Equatorial F-region irregularities generated by the Rayleigh-Taylor instability mechanism – rocket observations from Brazil
Authors P. Muralikrishna and L.P. VieiraSeveral sounding rockets carrying plasma diagnostic experiments were launched from the Brazilian rocket launching stations in Natal (5.9°S, 35.2°W Geog. Lat.) and Alcantara (2.31°S, 44.4°W Geog. Lat.). Langmuir Probes (LP) were used to measure the height profiles of electron density and electron temperature and High Frequency Capacitance (HFC) probes were used to measure electron density. The LP’s were also used to measure the amplitude of electron density fluctuations ranging in scale size from a few meters to several kilometers. A detailed study of the characteristic features of large scale electron density irregularities observed by rocket-borne electron density probes under different ionospheric conditions is presented here. The main objective of these studies is the identification of these irregularities from the point of view of the dynamic and eletrodynamic processes responsible for their generation. The existing theories of the Rayleigh Taylor Instability mechanism are adapted for conditions of the geomagnetic equatorial ionosphere over Brazil. Appropriately modified equations are used to estimate the minimum expected wavelength of the irregularities, the minimum growth time of irregularities, and the wavelength of irregularities corresponding to the minimum growth time. Through these parameters it is possible to discuss about the importance of the RTI mechanism for the ionosphere. The observed characteristics of the irregularities during four rocket launches are compared with the theoretically expected characteristics. These results confirm the operation of a cascade process that is responsible for the generation of a wide spectrum of irregularities. The cascade process is initiated by conditions favourable for the operation of Gradient Drift Instability (GDI) mechanism, though the growth times expected from theories do not always match with the observations. The large scale irregularities are first generated probably by the RTI mechanism that creates conditions favourable for the operation of the GDI mechanism. From the k-spectra of irregularities it is possible to obtain the spectral index n corresponding to the height chosen. In most of the cases the estimated spectral indices agree well with those published in the literature for the cases of irregularities generated by the GDI mechanism.
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Temporal dynamics and chaotic intermittency in nonlinear wave-wave interactions in space plasmas
Authors Rodrigo A. Miranda, Abraham C.-L. Chian and Erico L. RempelA nonlinear model of three-wave interactions and its temporal evolution is studied. First, we revise the techniques used to obtain the model. Starting from the MHD equations, we found an electrostatic expression for the Zakharov equations, which in the static approximation yield to the Nonlinear Schrödinger equation. The model is finally obtained using a three traveling wave truncation consisting in one linearly unstable pump wave and two linearly damped daughter waves. Then we proceed with the nonlinear dynamics analysis by constructing a bifurcation diagram, where we found a period-3 window. Examples of intermittency driven by temporal chaos present in the time series are shown. Some reviews of in-situ experiments and observations related to wave-wave interactions, and the relevance of the studied model are discussed.
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Modelo para Cálculo da Coluna Total de Ozônio usando Dados do Espectroradiômetro do Observatório Espacial do Sul
The ozone total column has been obtained through UV Radiation detectors as Radiometers and Spectroradiometers. It was used as an alternative method for stations which does not have expensive equipments to measure ozone like Brewer Spectrophotometers. The aim of this work is to find a mathematic model using the relation between UVB/UVA radiations ratio measured by Spectroradiometer MS 701 and effective ozone measured by Brewer Spectrophotometer MKIII #167. Both equipments are installed at Southern Space Observatory, at southern Brazil. The period selected for this analysis was the year of 2003 and only clean sky days were used. The mathematic model found was an exponential function with a correlation coefficient about 0.85. The effective ozone data obtained by Spectroradiometer were fitted with the model found and compared with the Brewer and TOMS ozone total column. The average difference between the model results and Brewer ozone total column was 0.7% and between the model and TOMS ozone data was 3.1%. It verifies the efficiency of the method used and a good approximation of the model.
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Atividade de Ondas de Gravidade na Estratosfera Terrestre Inferida Através da Técnica de Rádio Ocultação de GPS
More LessNeste trabalho são apresentados alguns resultados da atividade de ondas de gravidade na estratosfera sobre a América Latina, inferida através da técnica de rádio ocultação de GPS. Os dados utilizados foram obtidos pelo satélite Challenging Minisatellite Payload (GPSCHAMP). Também serão apresentados, a teoria e a metodologia empregada no cálculo da atividade das ondas de gravidade.
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A Técnica de Rádio Ocultação de GPS como Ferramenta para o Estudo da Atmosfera Terrestre
Authors Cristiano Max Wrasse, Hisao Takahashi and Joaquim FechineNeste trabalho será descrita a técnica de rádio ocultação de GPS e as suas potencialidades para o estudo da atmosfera terrestre, bem como as diversas áreas da ciência em que esta técnica vem sendo empregada.
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A Conductivity Model for the Brazilian Equatorial E-Region
More LessIn this paper we present field-line-integrated local ionospheric conductivity model for the Brazilian equatorial region. It was developed aiming to calculate the E-region electric fields that drive the 3-meter plasma irregularity of the equatorial electrojet. This model was based on the neutral atmosphere and electron densities, on the ion composition, and on E-region critical frequency foE measured by digisonde. Due to the large magnetic declination angle in the Brazilian sector we approximate the geomagnetic field model with a dipole which is not located at the centre of the Earth. We have also considered the eccentric dipole having an inclination of 20° with respect to the Earth rotation axis. The local conductivities resulting from our model are compared to the local conductivities obtained from the conductivity model of the Kyoto University.
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Ozone Hole Depletion over Brazilian Antarctic Station in the spring 2003/2004
More LessWe present measurements of ozone and UV-B radiation made in Brazilian Antarctic Station on King George Island (62.1°S; 58.4°W), during 2003/2004 spring. A field campaign was organized to measured the ozone using a ground based Brewer spectrophotometer, filter photometers, and the vertical profile was obtained on several days using balloon-borne ECC ozonesondes. During this period the UV-B radiation were also measured daily with the Brewer spectrophotometer. 13 successful ozone soundings were obtained during September and October 2003 and 6 ozone soundings were launched during October of 2004. The comparison between 2003 and 2004 these soundings showed severe depletion of stratospheric ozone, mostly in the lower stratosphere, which reached a maximum on October 06 2003, with 60% the reduction on ozone concentration and 2004 the maximum depletion was on October 14, with reduction of the 40%. During 2003 the total ozone content varied considerably: between 121 Dobson Units (DU) on October 06 and 391.6 DU for November 03 and the occurrence the minimum total ozone was the 35 days showing 16 consecutive days. During 2004 the ozone depletion was present 22 days with 11 consecutive days.
The comparison of the total ozone content measured by the ozonesondes with the total ozone Brewer spectrophotometer that operates from the ground has also been used during the campaign, giving a percentage difference of 3.9 + 2.4%.
In terms of the UV-B index, higher values were seen during 2003: on two occasions the Index passed the level of 9; which is larger than values observed on any campaign at the site. During the end of September and the beginning of October the index running mean reached 6, while during the 2004 equivalent period the higher value was about 6.8 and the running mean reached 3.3.
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Comparative study of the ionospheric characteristics of two low latitude Brazilian stations
Authors F. Bertoni, W. Lima, P. Fagundes, F. Becker-Guedes and Y. SahaiWe present, in this paper, a comparative study of ionospheric parameters obtained by two digital ionosondes located at the Brazilian stations of Palmas (10.17°S, 48.20°W) and São José dos Campos (23.21°S, 45.86°W), during periods of geomagnetically quiet days of the equinoctial months of September, October and November 2003. It is suggested that some of the differences between the ionosphere behaviors over those locations to be related to seasonality and some to geographic and geomagnetic configurations.
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Observações simultâneas da emissão do OI 630 nm da Aeroluminescência Noturna através de Fotômetros nos Observatórios Espaciais de São Martinho da Serra (OES) e Cachoeira Paulista (CP)
Este trabalho visa estudar o comportamento das “Bolhas de Plasma” na Ionosfera observando a emissão da Aeroluminescência do oxigênio OI 630 nm em dois sítios observacionais na mesma Latitude Geomagnética, um em São Martinho da Serra, RS (29°S, 53°W, -33° dip latitude), e o outro em Cachoeira Paulista, SP (22.7°S, 45°W, -34° dip latitude). Foram realizadas as medidas simultâneas das variações temporais da intensidade de emissão OI 630 nm no período de janeiro de 2000 a fevereiro de 2005. Para o
presente trabalho foram escolhidas quatro noites quando com ocorrência de “Bolhas de Plasma” nos dois locais. Observou-se nos eventos uma assimetria em relação ao número de “Bolhas” e simetria em relação à intensidade da emissão medida. A análise estatística sobre a ocorrência das “Bolhas” está sendo desenvolvida.
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Modelo Empírico para determinação do Índice UV, obtido com dados do Radiômetro e do Biômetro para o Observatório Espacial do Sul
The Ultraviolet Index was created to advise the population about the solar exposure risk. It can be obtained through biologically active radiation detectors or UV detectors able to measure the irradiance for each wavelength. A network of UV – B Radiometers were installed in cities as: São Martinho da Serra – Brazil, Punta Arenas – Chile, Concepcion – Argentina and Rio Grande – Brazil, through a cooperation between the Tokushoku and Rikkyo Universities, in Japan, the Federal University of Santa Maria and the Southern Regional Space Research Center of the National Institute for Space Research, in Brazil. These equipments measure the accumulated UV Radiation in the spectral range from 280 to 315 nm, which does not permit the radiation be weighed with the Erythema Action Spectrum (Mckinlay-Diffey). The aim of this work is to calculate a model which infers the Ultraviolet Index by UV – B Radiometer MS 210 W data using a Biometer 501 A as reference. The equipments used in this analysis are installed at Southern Space Observatory SSO/CRSPE/INPE – MCT, in São Martinho da Serra, RS – Brazil. The period selected for this analysis was the months of June and November of 2003. Two functions were obtained comparing the Biometer and Radiometer data, one for each month. The models obtained made possible the calculus of the Ultraviolet Index. The correlation coefficients obtained by the models are 0.95 for June and 0.96 for November.
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Ventos Mesosféricos no Sul do Brasil
The Radar System of Meteoric Trails - "All-Sky Interferometric Meteor Radar - SKiYMET", makes it possible the study of Mesosphere in the South of Brazil, in the geographical center of Rio Grande do Sul. Of all theexistent techniques to study the winds in the middle atmosphere, only the ones that use radars and, meteoric radars specially, allows the continuous study in long periods, making possible the evaluation of the diurnal and seasonal variations on winds. The radar technique is based on the determination of average speed of the neutral winds, through the radial speed of the meteoric trails. When penetrating in the atmosphere in high speed, the cosmic particles suffer ablation and produce long ionized columns, which are moved by neutral winds. The movement of these particles produces a Doppler displacement in the sign reflected by the meteoric trail. From this displacement, the radial speed of the meteor can be determined, and together with other information, the position, the speed and direction of the wind also can
be determined.
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Estudo da estrutura vertical da emissão OI 630,0 nm na camada F na região tropical brasileira
Authors C.M.N. Cândido, P. R. Fagundes, J. R. Abalde, V. G. Pillat, D. Gobbi and H. TakahashiIn this paper we present the optical study using the OI 630,0 nm all-sky imaging observations, which occurs in the bottom side of the F layer, between 250 and 300 km altitude. This study is based on the simultaneous observations of the emission OI 630,0 nm which are performed by two similar all-sky imaging systems, based on CCD system set up at two separate sites, Brazópolis, MG (22,53S; 45,57W; Dip Latitude 17,47S) and Cachoeira Paulista, SP (22,7S; 45,0W; Dip Latitude 17,95 S) and São José dos Campos, SP (23,21S; 45,86W; Dip Latitude 17,61S). Applying the triangulation method we analyze two simultaneous images obtained at pair of stations and we derive the altitude of the emission layer.
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A preliminary study of global and diffuse solar radiation data from a SONDA station located in São Martinho da Serra, RS - Brazil (29.44ºS, 53.82ºW)
The aim of this work is to present a preliminary study of the incident solar radiation data, measured by the SONDA station of São Martinho da Serra, RS, Brazil. The global solar radiation and one of its components, the diffuse radiation, are compared each other and with some correlations and results found in the technical literature. Data produced by pyranometers in the period from July/2004 (station installation) to March/2005 were used. It was found a good agreement between the observational data and results already published. Some of the observed differences were discussed. However, a longer period of data is necessary in order to create models correlating the global and diffuse radiation for this station.
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Variação sazonal do airglow do sódio mesosférico em 7,4ºS em torno da atividade solar máxima 23
Authors F.E. Gomes, R.A. Buriti and A.F. TakahashiThe mesopheric sodium airglow emission occurs when the sodium atom decay from excited level 2S to level 2P, emitting at the line D in λ=589.3nm. Measurements of the emission nocturnal intensity havebeen carried by a multichannel photometer installed at S. J. do Cariri (7,38°S;36,5°O) since 1998. In this work was analyzed a data set correspondent to a period from 1998 to 2003, in order to study the emission seasonal comportament. The analyses showed that a strong seasonal variation. The results are in accordance to others studies realized at equatorials regions. The relationship between solar activity and NaD emission showed a concordance during ascendency and decay of the solar activity, but have discrepance during peak of the solar activity.
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Detecção de TIDs nas regiões sub-auroral e da Anomalia Magnética do Atlântico Sul
Gravity waves propagating to thermospheric heights and interacting with the ionospheric plasma give rise to Traveling Ionospheric Disturbances (TID). These are visible as amplitude, phase and frequency (period) quasi-periodical fluctuations of a radio signal reflected from the ionosphere and/or a variation of cosmic noise absorption intensity in the lower ionosphere. This work presents a gravity wave study obtained from cosmic noise absorption recorded by riometer from 1989 to 1996 in the Brazilian Antarctic Station (EACF) (sub-auroral region – 62.56oS; 58.39oW) and the South Atlantic Magnetic Anomaly Region (SAMA) (Cachoeira Paulista – 22.50oS; 45.00oW). The results obtained present the occurrence dominance of the median scale TIDs in the sub-auroral region while in the SAMA region the large scale TIDs occurrence were dominant. This analysis also shows that the sub-auroral region is more prone to occurrence of TIDs than the SAMA region, independent of its period. The results show a close relationship of the medium scale TID occurrence increase with the geomagnetic activity and with the Dst index decrease (periods of the magnetic storms and sub storms) in the sub-auroral region and in the interplanetary shock periods (positive fase of the magnetic storms). In the SAMA region it was found a possible response to the large scale TIDs with the periods associated with magnetic storms and/or sub-storms.
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Modelo numérico da baixa ionosfera
More LessThis work presents lower ionosphere simulations performed by the BLIC model (Brum Lower Ionosphere Chemistry model) compared with the Sheffield University Plasmasphere Ionosphere Model-Enhanced (SUPIM-E) simulations of the South Atlantic Magnetic Anomaly region (SAMA) and Sodankylä Ion Chemistry model (SIC) simulations and rocket data over the Andoya (Norway) region. These results show a good consistence in the simulations for the different regions and conditions. The simulations performed for the SAMA region showed excellent agreement, mainly with the ionospheric E region height peak. Therefore, below this peak, it was found a little difference between the electronic density profile simulations during solar minimum activity condition, produced by the different sources of ionization radiation sources used by the SUPIM-E and BLIC models. Also, good agreement was found among SIC, BLIC simulations and rocket data over the Andoya region, mainly under 90km hight. Over this altitude it was verified a small difference in the profiles computed by BLIC and the profiles computed by SIC and obtained by rocket experiment due to the chose precipitated electron spectrum.
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Chaos and intermittency in interplanetary Alfvén waves
More LessIn this paper we present an investigation of intermittency in interplanetary Alfvén waves modeled by the DNLS equation. We show how the fluctuations of the magnetic field can evolve from periodic to chaotic dynamics, where two types of intermittency are identified: type-I Pomeau-Manneville and crisis-induced intermittency. The characteristic intermittency time follows a well defined power-law as a function of the plasma viscosity.
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Simultaneous ionospheric sounding observations from the equatorial and low latitude regions in the Brazilian sector during the super geomagnetic storm on 20 November 2003
Authors F. Becker-Guedes, Y. Sahai, P. R. Fagundes, Su. Basu, Sa. Basu, W. L. C. Lima and and V. G. PillatDigital ionosondes, of the type known as the Canadian Advanced Digital Ionosonde (CADI), have been in routine operation at São José dos Campos (low latitude region) and Palmas (equatorial region), Brazil, since August 2000 and April 2002, respectively. These CADIs are part of a new network established in a collaborative program between UNIVAP and CEULP/ULBRA. The main objective of the network is to study the equatorial and lowlatitude ionospheric regions in the Brazilian sector during both quiet and geo-magnetically disturbed conditions. In this work we present the results of the ionospheric observations related to the superstorm (|Dst|max > 250 nT) on 20 November 2003 in the Brazilian sector, as evidenced by the ionospheric parameter changes from simultaneous ionospheric sounding observations carried out at São José dos Campos and Palmas. A comparison of the observed ionospheric response at the two stations, separated only by about 1460 km, shows considerable latitudinal differences associated with the geomagnetic disturbances. Both the stations show copious storm-time changes.
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Terdiurnal tides in MLT region over Cachoeira Paulista (22.7º S; 45º W)
Authors Aparecido S. Tokumoto, Paulo P. Batista and Barclay R. ClemeshaFive years of winds measurements obtained by a SkiYmet meteor radar at Cachoeira Paulista (22.7° S, 45.0° W) are used to investigate the terdiurnal This type of tide is frequently observed in the meteor region but the mechanisms responsible for its production are not yet completely explained. Among the possible causes are solar direct forcing and nonlinear interactions between the diurnal and semidiurnal tides. Nonlinear interaction between diurnal and semidiurnal tides can generate two secondary waves: a diurnal tide and a terdiurnal tide. The origin and distribution of the terdiurnal tide may indicate the presence of a secondary diurnal tide as a cause of variability in the primary diurnal tide. In this work we analyze the winds data in search of evidence for these mechanisms.
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Behavior of the equatorial ionosphere over Palmas-TO during geomagnetic quiet days
Authors W. Lima, F. Bertoni, P. Fagundes, F. Becker-Guedes, Y. Sahai and Abalde J. RThis work presents a study of the ionospheric parameters obtained a digital ionosonde type know as Canadian Advanced Digital Ionosonde – CADI located Palmas (10.17°S, 48.20°W), Brazil for the winter month of July and the equinoctial month of September. A comparison of the ionospheric parameters (h´F, hpF2 and foF2) for the 2002 and 2003 year during periods of geomagnetically quiet days, although similar, shows same significant differences during particular periods.
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Quasi-2-day wave observed in the equatorial and low latitudes MLT regions of the Southern Hemisphere
Simultaneous observations of the atmospheric neutral winds in the mesosphere and lower thermosphere (MLT) region by meteor radar have been carried out at São João do Cariri (7.4° S, 36.5° W) and Cachoeira Paulista (22.7° S, 45.0° W). From the wind variability we investigate the planetary-scale quasi-two-day waves, which are present at both the sites during the winter of 2004 and summer of 2004/2005. The amplitude of the meridional component was larger than that of the zonal component, reaching a maximum value of ~60 m/s at the equatorial site and ~25 m/s at the low latitude site during the winter. During the January-February period the 2-day wave was very similar at the two sites, with a maximum amplitude of ~50 m/s. The phase propagation with height shows a descending mode and upward energy propagation. The vertical wavelength estimated for Cachoeira Paulista was longer than for São João do Cariri, for all of the observed events. Cross-spectral analysis showed a significant coherence between the quasi-two-day oscillations observed at the two sites. From the phase difference between the two sites we concluded that São João do Cariri leads Cachoeira Paulista. These results are compatible with a westward propagating wave.
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Diurnal and semidiurnal variations in the mesospheric winds observed at São João do Cariri-PB, Brazil: a preliminary study
The terrestrial atmosphere is a dynamical system in which periodic oscillations are present and play a significant role in the dynamics of the upper mesosphere and low thermosphere (MLT). It is already well known that atmospheric tides play an important role in the dynamics of the MLT region, and the purpose of this study is to extend our knowledge of diurnal and semidiurnal oscillations in the equatorial MLT region, taking advantage of the measurements of meteor winds over São João do Cariri, Brazil (7° S, 36° W), which started in June 2004. In a preliminary analysis, we have observed that both wind components exhibited variability with respect to both time and height. Diurnal and semidiurnal oscillations also exhibited time and height variability. In general, the diurnal and semidiurnal amplitudes for meridional wind component were larger than the zonal component. From the phase structure, it was found that the vertical wavelength of the diurnal variations assumed values from 21 to 26 km for the meridional wind component, whereas for semidiurnal variations, the vertical wavelengths assumed values between 50 and 90 km.
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Ionospheric plasma drift at low latitudes
Trans-equatorial F region plasma bubbles are large-scale ionospheric depleted regions that develop in the bottomside of equatorial F region due to plasma instability processes. Simultaneous all-sky imaging observations of the OI 630.0 nm and OI 777.4 nm nightglow emissions were carried out at São José dos Campos (23.21oS, 45.86oW; dip latitude 17.6oS), Brazil, during the years 2000 and 2001, a period of high solar activity. In this work we present and discuss the height-resolved nocturnal F region zonal drift velocities obtained from plasma bubbles observed in imaging observations of these two emissions for several days of 2000 and 2001. We have investigated the nighttime zonal plasma drift variations using fixed emission peak altitudes, used by earlier investigators, as well as emission peak altitudes based on simultaneous ionospheric sounding observations. The average maximum and minimum zonal plasma drift velocities inferred for both the emissions, using emission peak altitudes based on simultaneous ionospheric observations are lower and with less scatter than those using fixed emission peak altitudes. Also, the nocturnal variations of the zonal plasma drift velocities obtained for the two emissions with peak altitudes based on simultaneous ionospheric observations show better agreement than for the case with fixed emission peak altitudes.
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Forbush decreases in November 6-20, 2004 observed by the Muon Detector Network
In this paper we study the relationship between Interplanetary Coronal Mass Ejections (ICMEs) and the count rate muon decrease detected by the muon detector network in November 6-20, 2004. The Muon Detector Network is composed by the detectors installed in Nagoya (Japan), Hobart (Australian) and the prototype detector installed in the “Observatório Espacial do Sul – OES/CRSPE/INPE-MCT”, located in São Martinho da Serra, RS, Brazil. With the muons count rate observed by the Muon Detector Network, we will be able to observe, in the future,the direction in which a given ICME moves, and with that, we will be able to calculate the angle which they reach the Earth. Also, with this muon network, we will be able to send alerts of up to 12 hours before the arrival of a shock or an ICME. The Space Weather forecast method using cosmic rays will be a very important tool because it provides a forecast with good antecedence.
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Methane emissions from lakes in Pantanal – Methodology and preliminaries results
Authors Luciano Marani and Plínio C. AlvaláThe methodology and the preliminaries results of a study to evaluate the methane (CH4) emissions from lakes and floodplains in Pantanal are presented. The sample sites are chosen to represent different environmental characteristics on the region. The methane fluxes are obtained by the technique of static chamber. The work had begun in 2004 and extends for 2005, with sampling campaigns every 3-month (March, June, September and December of each year). The preliminaries results obtained during 2004 (March, June and September) shows a overall average flux of 79.3 ± 227.1 mgCH4 m-2d- 1, ranged -8.7 to 1983.1 mgCH4 m-2d-1 and also indicates that methane fluxes are influenced by the water depth and by the presence of aquatic vegetation. The fluxes
could be divided in terms of the way of methane transport through the water column in diffusive and bubble fluxes, and each one are influenced by water depth and vegetation in different ways.
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Comportamento sazonal de Bolhas de Plasma na região equatorial do Brasil observado pelo imageamento do airglow na emissão do OI 630,0 nm
Authors Igo Paulino, Amauri Fragoso de Medeiros and Ricardo Arlen BuritiThe study of the ionospheric irregularities or plasma bubbles is very important for to understand the dynamics process of the high atmosphere. The variability is a determined element in the preview of the space weather, thus the short time preview of the behavior of the bubbles is indispensable for the plain of the activities and the system of special application. In this paper we present results of two years (from September 2000 to l August 2002) of observations of the plasma bubbles through imager all sky data localized placed at São João do Cariri (7°13’S; 35°52’W). The plasma bubble showed a seasonal behavior characterized by appear between moths September and Mach of the two years observed, while in the others moths we detect few times the plasma bubble. However, we can see too that during the equinox moths the occurrence peak of the bubbles happened more early (~20:30 LT) than summer moths where the occurrence peak was around of 21:30 until 23:30 LT (Local Time). In the summer the plasma bubble occurrence was larger than equinox moths. The dynamics conditions of ionospheric plasma are dominated by electromagnetic drift ExB and depended of the conductivity across field magnetic lines in the E conjugates regions and, thus, the alignment between the magnetic meridian and the solar terminate is the responsible by bubble seasonal variation, as well as, by major occurrence this phenomenon in the summer months.
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A Statistical study of the Application of Incoherent Integration to Simulated Equatorial Electrojet Irregularities Power Spectra
The RESCO 50 MHz coherent back-scatter radar has been operated since 1998 at the INPE/MCT’s São Luís Space Observatory (2.33° S, 44.2° W, DIP: -0.5°), Brazil, on the dip equator to study the equatorial electrojet dynamics. Spectral analysis of the received echo from equatorial electrojet irregularities allow us to identify the dominant type of plasma irregularities in the electrojet bulk observed by the radar. Using curve fitting methods on the resulting power spectra it is also possible to obtain other characteristics from the echoes, such as: center of frequency distribution, spectral width and power. The usual approach in this analysis is through a Gaussian fitting based on the method of Least Square Error to parameters estimation. Before fitting the power spectra it is usual to smooth it in order to reduce the noise level and define better the center of frequency distribution. From the center of frequency distribution, we are able to deduce the Doppler shift of the irregularities in relation to the radar, which is close related to the electric fields that drives the plasma instabilities. In this work, we have simulated echoes signals from 3-meter type 1 plasma instabilities, and analyzed it in order to recover the center of frequency distribution used to simulate the data generated. As a smoothing method we have use dincoherent integration. We have applied three distinct levels of smoothing in order to evaluate the response of the fitting to this technique. The advantages and disadvantages of applying different levels of incoherent integration over power spectra of back-scatter echoes from type 1 irregularities in the parameter estimation are presented and discussed.
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AIR POLLUTION EPISODES ASSOCIATED WITH LONG RANGE TRANSPORT OF BIOMASS BURNING PRODUCTS
Authors Cláudia Boian and Volker W. J. H. KirchhoffAn experiment was performed in the north-west of the state of Paraná, at Maringá site (23.10 S; 51.10 W), from August 2001 to November 2002, to determine the impact of large scale transport, over a distant region of the biomass burning area, under the influence of the anticyclonic circulation. This is a typical local transport regime during the dry season (July-September), when intense biomass burning occurs in Central Brazil, and which gives origin to the transport of burning products from the sources to distant regions in the south of the continent. Simultaneous measurements of carbon monoxide and ozone were made in Campo Grande (20S; 54W), a moderate biomass burning region. Campo Grande is a continental site located in the Mato Grosso do Sul state, which was used as a temporary site for the present study. Vertical ozone profiles, surface carbon monoxide and ozone measurements, were compared with backward trajectories, fire pixels seen by the AVHRR satellite and meteorological conditions to determine the influence of the large scale transport at Maringá. An instrumented air-conditioned trailer was installed in a rural area (northeast of Maringá), distant some 15 km from downtown, for continuous and systematic surface ozone measurements. CO measurements were obtained from grab samples, collected weekly. The air samples were then taken to the laboratory where they were analyzed for CO by gas chromatography. Electrochemical concentration cell (ECC) ozonesondes were used to measure the vertical ozone profile. The lowest concentrations were measured in January (carbon monoxide average 110.8 ± 11.8 ppbv and ozone average 13.2 ± 4.0). These values were used as reference background values in our analysis. A clear increase in trace gas concentrations was observed in Maringá during the dry season (from August to October) when intense biomass burning occurs in Central Brazil and the transport term is more significant. An excess of four times the background value of CO was observed in Maringá during this period. Excess ozone was also observed from surface measurements and vertical ozone profiles.
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ASSOCIATION BETWEEN IONOSPHERIC PLASMA BUBBLES AND SPREAD-F
A statistical study of the association between the frequency of occurrence of the ionospheric bubbles and the range spread-F (large-scale ionospheric irregularities) is presented here. This study was based on radio frequency observations (Digisonde data) and optical observations of the airglow OI630nm by an all-sky digital imager system located at the low-latitude region – Cachoeira Paulista (22.5oS, 45oW) – and at the equatorial region – São João do Cariri (7.4oS; 36.5oW). A total of 158 nights during maximum solar cycle were analyzed being 63 nights at Cachoeira Paulista and 95 nights at São João do Cariri. The frequency of occurrence of ionospheric bubbles at Cachoeira Paulista was compared with frequency of occurrence of the range spread-F over the same site. At São João do Cariri, the frequency of occurrence of the ionospheric bubbles was compared with the frequency of occurrence of the range spread-F over São Luis (2oS; 44oW) and Fortaleza (3.5oS; 38.2oW) because unfortunately there is not a Digisonde operating at São João do Cariri. This statistical study with the local time showed that the ionospheric irregularities occur with high frequency between October and March. Also, it was observed that the occurrence of ionospheric bubbles is closely related to the occurrence of the range spread-F. The observations showed that the frequency of occurrence of ionospheric bubbles in Cachoeira Paulista is greater than the frequency of occurrence of the range spread-F. Apparently, this fact occurs because of the discrepancies between the areas of covering of each instrument utilized.
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Extension of the non-linear depth imaging capability of the inverse scattering series to multidimensional media: strategies and numerical results
Authors F. Liu, A. B. Weglein and K. A. Innanen and B. G. NitaThe inverse scattering series (ISS) has proven, and continues to prove, to be a highly effective formalism for the separate and isolated accomplishment of several key tasks of reflection seismic processing and inversion. In particular, Weglein et al. (2000), Shaw et al. (2003), and Shaw (2005) describe the development of an algorithm distilled from the ISS that concerns itself with the location of subsurface reflectors with no prior knowledge, or related intervening estimation, of the medium wavespeed. The specific non-linear data activity that accomplishes this goal has been investigated by Shaw as such for an idealized 1D pre-stack acoustic experiment; we here describe the extension of those ideas to accommodate media with lateral variation. This is a non-trivial step.
Nevertheless, beneath the added algebraic complexity, recognizable patterns and mechanisms are visible. Analysis of these terms and patterns suggests that certain portions of the 2D reflector location mechanisms of the ISS are a good starting point for the creation of algorithms for the accurate depth location of reflectors with a moderate level of lateral variability. The partial 2D imaging capability within the ISS is examined in this paper for the special case of a constant density acoustic medium and taking kh=0. We demonstrate numerical implementations of these forms and discuss ongoing work towards capturing further imaging capability residing within the ISS, especially with regards to the accommodation of larger levels of contrast and rapidity of spatial variation in medium properties.
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Common-Reflection-Surface stack – a generalized stacking velocity analysis tool
By Jürgen MannThe Common-Reflection-Surface (CRS) stack has originally been considered as an alternative stacking tool to simulate high quality zero-offset section from seismic multicoverage data. Meanwhile, this perception has significantly changed in favor of the stacking parameters employed in the CRS stack. The fully automated determination of these parameters during the CRS stack can be seen as generalization of the well established stacking velocity analysis applied in the conventional NMO/DMO/stack approach. As
the CRS stack accounts for local dip and curvature of reflectors in depth, its stacking parameters carry far more information about the subsurface than conventional stacking velocity. Consequently, applications based on such stacking parameters, e. g., velocity model determination, directly benefit from this generalization: more stable results can be achieved in a more automated manner with less rigorous constraints compared to conventional methods. I briefly review the basic concepts of the CRS stack method and illustrate them with a data example. The main message is that this method facilitates various imaging problems, e. g., inversion, depth imaging, and automated horizon picking.
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Detecting reservoir fractures and their orientation using multi azimuth walkaway VSP
More LessFour walkaway VSP lines were acquired in the Kashagan East 1 well located in the Caspian Sea. Fracture orientations in the reservoir were obtained by acquiring data from multi azimuths and offsets recorded with several 3-component geophones lowered into the carbonate zone. Orientations were detected by interpreting the polarization of the fast and slow shear waves (figure 1) observed in the horizontal geophone component data.
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Offset VSP in a deviated well to get converted shear waves
This paper presents a case history in which the main objective of the borehole seismic survey was to obtain information about converted shear waves, in order to support the evaluation of feasibility for an OBC project in a Tertiary reservoir, Offshore Brazil. The Offset VSP has shown a large degree of P to S conversion, at different layers. The well trajectory in combination with the source position allowed to get Shear velocities, and also to generate P and S images that provided an additional tool to evaluate the degree of P to S conversion.
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Seismic phase and amplitude calibration deep-water Brazil using VSP data
Authors Rafael Guerra, Carlos Rodriguez and Scott LeaneyIn this paper we review a case study where borehole seismic data acquired in a deep-water field offshore Brazil, was used to build a 1.5D-anelastic model that accurately predicts the seismic amplitude attenuation versus time and offset, due to the combined effects of geometrical spreading, transmission losses and anelastic attenuation (Q-factor). This borehole calibrated model is ray-traced to compute a seismic amplitude gain function that can be applied directly to surface seismic pre-stack gathers and the results compared to the geometrical spreading correction conventionally used. The Q(z) profile derived from the VSP data provides also very useful information for high-frequency enhancement of seismic data. Finally, we show the use of VSP data in assessing
the phase of different vintages of surface seismic data and their degree of well tie.
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