PreviousNext No Access11th International Congress of the Brazilian Geophysical Society & EXPOGEF 2009, Salvador, Bahia, Brazil, 24-28 August 2009Anti-correlation between magnetic storms and ionospheric scintillation observed at stations in the equatorial anomalyAuthors: R. Y. L. C.E. R. de PaulaE. BonelliR. Y. L. C.Instituto Nacional de Pesquisas Espaciais/DAE, São José dos Campos, São Paulo, BrazilSearch for more papers by this author, E. R. de PaulaInstituto Nacional de Pesquisas Espaciais/DAE, São José dos Campos, São Paulo, BrazilSearch for more papers by this author, and E. BonelliDepartamento de Geofísica, Universidade Federal do Rio Grande do Norte, Natal, Rio Grande do Norte, BrazilSearch for more papers by this authorhttps://doi.org/10.1190/sbgf2009-028 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract Ionospheric scintillations are due to the presence of plasma irregularities in the ionosphere, which show seasonal dependence (occur in September-March) and with greater intensity during periods of high solar activity. It was studied the effect of magnetic storms on the ionospheric scintillations during the maximum (1999-2001) and minimum (2006-2007) of solar activity. To represent the intensity of the scintillations, it was used hourly averages scintillation index S4 of São José dos Campos and Cachoeira Paulista stations (under the peak of the Equatorial Ionization Anomaly - EIA), São Luís and Natal (near the valley of the EIA) and Cuiabá (between valley and peak of the EIA). Using the geomagnetic indices Kp and Dst to represent the magnetic activity, it was found an anti-correlation in the GPS amplitude during the storm main phase. This represents an improvement of the GPS signal reception during magnetic storms. This inhibition of scintillations is associated with penetration of electric fields from the disturbed dynamo, which inhibit the formation of the prereversal peak plasma vertical drift, which is one of the main factors in the generation of plasma irregularities in the ionospheric F region. The prereversal peak inhibition and consequently a decrease in the S4 scintillation index occurs predominantly when the storm main phase happens in the range of 1000 to 1600 LT. In this study it is analyzed the relation between S4 and Dst indices during this local time interval. Keywords: aeronomy, ionospheric, magnetic, GPS, solarPermalink: https://doi.org/10.1190/sbgf2009-028FiguresReferencesRelatedDetails 11th International Congress of the Brazilian Geophysical Society & EXPOGEF 2009, Salvador, Bahia, Brazil, 24-28 August 2009ISSN (online):2159-6832Copyright: 2009 Pages: 1997 publication data© 2009 Published in electronic format with permission by the Brazilian Geophysical SocietyPublisher:Society of Exploration Geophysicists HistoryPublished Online: 28 Apr 2014 CITATION INFORMATION R. Y. L. C.Cueva, E. R. de Paula, and E. Bonelli, (2009), "Anti-correlation between magnetic storms and ionospheric scintillation observed at stations in the equatorial anomaly," SEG Global Meeting Abstracts : 111-114. https://doi.org/10.1190/sbgf2009-028 Plain-Language Summary KeywordsaeronomyionosphericmagneticGPSsolarPDF DownloadLoading ...

Amplitude scintillations in satellite signals can cause errors in communications, because of signal fading, but can be very useful for scientists trying to improve their understanding of the physics of the ionosphere. Usually, magnetic storms are expected to affect the ionosphere in such way as to increase ionospheric irregularities responsible for scintillations. To help change the view of scientists and engineers, in this respect, we show that amplitude scintillation on GPS signals show dramatic decrease during selected magnetic storms, at Brazilian GPS stations. These stations are located on magnetic latitudes that go from equatorial (São Luís) to low‐latitude (São José dos Campos and Cachoeira Paulista) so that a region of several thousand kilometers is represented by the data. We present 4 months of data chosen from 2003 to 2005 to represent the strongest storms during each scintillation season. Although there is lack of data for some days from the different stations, it is possible to see, especially for the Halloween Storm (October 2003), that scintillations are attenuated in this wide range of latitudes. During magnetically calm periods scintillations are strong, in this region, from August to March, during solar maxima. Although the data are clear about the attenuation of scintillations during greater magnetic storms, it is not possible to easily conclude which physical mechanism was responsible for this phenomenon, even with the aid of more detailed data like Dst and AE.

The following paper describes the test activities performed at AEROSPAZIO during a 3000 h endurance test carried out on the RIT-22 thruster. In particular, the paper describes the vacuum data and the beam diagnostics test results. The test activities were aimed at performing a continuous firing of the RIT thruster at the selected nominal operating point corresponding to 175 mN of thrust. Characterisation tests (Perveance, Electron Back Stream) were performed at selected operating times. Beam diagnostics was performed approximately each 100 h of thruster operation. The test activities were performed in the new Aerospazio large Vacuum Test Facility. The vacuum conditions were better than 6 x 10 -6 mbar during all thruster operations.

A Large Vacuum Test Facility has been developed at AEROSPAZIO Tecnologie with the aim of providing high qualified test services in Electric Propulsion and Space Simulation. The test facility consist of a stainless steel cylinder 3.8 m diameter and 11.5 m overall length. A modular cryopumping system allows 200.000 l/s continuous pumping speed of Xe. Beam diagnostics, including Faraday probes and Retarding Potential Analysers, have been installed. A test campaign aimed at evaluating the EMC characteristics of the test site has been performed.

Ionospheric Electron Content (IEC), measured at the Brazilian low latitude station of Cachoeira Paulista (22.5°S, 45°W, dip latitude 14°S) was compared with IEC calculated using the IRI-90 and Sheffield University Plasmaphere-Ionosphere (SUPIM) models for a large range of solar fluxes at 10.7 cm (F10.7). The analysis of the F10.7 influence on IEC showed that, for Cachoeira Paulista (CP) at 05 LT (around the diurnal minimum), there is a good agreement between the IEC measurements and the models. At 16 LT (around the diurnal maximum), substantial discrepancies were observed in the IRI-90 results while SUPIM presents a good agreement up to F10.7 ≈ 200. The measured IEC diurnal variation is better represented by SUPIM, mainly during higher F10.7. At low latitudes two critical parametric inputs for the SUPIM mathematical model are the equatorial ExB plasma drifts and thermospheric neutral winds. Therefore, updated values of these parameters should be introduced in the model calculations everytime they are available. At CP, a station located close to the southern Appleton anomaly peak due to the fountain effect, where large discrepancies between IRI-90 and observations were found mainly with high F10.7, this model should include adequately this effect, which we believe is the main reason for the discrepancies.

Two main forms of hamartomas are found in the lung, chondromas and hemangiomas. Hemangiomas occur either as single lesions or as diffuse pulmonary hemangiomatosis, which is a very rare but fatal disorder. The disease frequently manifests asymptomatically, and mainly in adults. Patients most often do not experience any symptoms and the disease manifests as late as in the adult age with cough, hemoptysis, chest pain and fever associated with pneumonitis. Usually, the disease progresses rapidly, and causes secondary veno-occlusive disease leading to pulmonary hypertension or bleeding. Diagnosis is difficult, and radiography often gives no evidence. There is need for an aggressive approach which in most cases is followed only after the onset of severe complications. In newborns these lesions are chiefly detected incidentally at autopsy; visceral hemangiomas do not regress spontaneously. Since an accurate diagnosis depends on open biopsy, conjoint resection can be easily performed in most instances, this may even become a necessity when complications occur. We report about 3 cases of pulmonary hemangiomas in newborn babies who were diagnosed shortly after birth and treated surgically during the first months of life. In 2 cases, surgical treatment cured the patients, 1 case took a fatal caurse. Early diagnosis may allow to restrict the surgical procedure and may in some cases even cure the patient, anyhow it prevents complications.

Incoherent scatter radar measurements at Jicamarca are used to study the effects of large solar fluxes and magnetic activity on the F region vertical plasma drifts. The average drifts from the two last solar maxima are almost identical except in the late afternoon‐early evening sector where their variations with solar flux and magnetic activity are strongly season dependent. The average evening winter (May‐August) drifts appear to remain almost constant after a certain solar flux level is reached but increase with magnetic activity. The equinoctial evening drifts increase systematically with solar‐flux but decrease with magnetic activity. Very large prereversal enhancement velocities, up to about 80 m/s, were often observed during the 1978–1981 equinoctial periods when the solar flux was very high. Comparison of incoherent scatter radar drifts with vertical velocities inferred from ionosonde observations indicate that the latter technique substantially underestimates the plasma drifts during periods of large solar fluxes except during winter.

The electric fields in the ionospheric E and F regions near the magnetic equator often show a strong eastward enhancement shortly after sunset and before the eastward (normally) daytime field reverses to westward. Several theoretical models of the low‐latitude fields suggest that this enhancement is caused mainly or entirely by F region winds (the F region dynamo), but some authors have suggested that it could be produced solely by E region tidal winds. We give here additional calculations and arguments in support of the F region source. The enhancement of the eastward field for an eastward F region wind turns out to be a simple direct consequence of the fact that after sunset the ionospheric conductivity decreases far more rapidly in the E region than in the F region.

By a sample record we show that the radio beacon experiments which utilize the Faraday rotation technique and the scintillation observations can be used to observe equatorial ionization bubbles. In a two‐hour period 5 isolated bubbles have been identified. The depleted total electron content for one such bubble is 2.2×1016 electrons/m² and the east‐west dimension is about 72 km. This translates to a total depletion of 1.6×1021 electron per meter in the north‐south direction.

A wireless application based on a PDA and a mobile phone has been developed at AEROSPAZIO Tecnologie to allow remote control of space test facilities and increase the staff mobility. The application developed in house has been compared with the available software over different networks. The test activities and results are described