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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
441 - 460 of 462 results
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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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