Navegando por Autor "Camargo, Paulo de Oliveira"

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    Advantages and disadvantages of VTEC, ROTI and airglow images in studying equatorial plasma bubbles
    (Elsevier) Souza, Ana Lucia Christovam de; Prol, Fabricio dos Santos; Muella, Marcio Tadeu de Assis Honorato; Picanço, Giorgio Arlan da Silva; Camargo, Paulo de Oliveira; Monico, João Francisco Galera
    Equatorial plasma bubbles (EPBs) are large-scale plasma depletion structures, observed near the geomagnetic equator and in low- latitude regions after sunset. Several instruments have been employed to study EPBs, such as ionosondes, in situ satellites, coherent and incoherent scatter radars, airglow imagers, GNSS radio occultation, and GNSS ground-based stations. Among these instruments, Total Electron Content (TEC) and Rate of TEC change Index (ROTI) data derived by GNSS measurements are presenting as outstand- ing data sources to study the climatology of EPBs. In this study, we evaluate the reliability of TEC and ROTI index for mapping iono- spheric plasma bubble structures in comparison to airglow images, demonstrating the performance of each technique and highlighting their respective advantages and disadvantages. The results demonstrate that TEC and ROTI time series are effective to identify plasma bubble occurrence in terms of temporal profiles, horizontal maps, and keograms for EPB velocity estimation. In terms of ionospheric temporal profiles, all techniques presented a good correspondence, TEC data may present direct characteristics of plasma bubbles, i.e., the intensity of the electron density depletions, while ROTI values are more suitable to present the occurrence, or not, of plasma bubbles. TEC maps showed advantages in mapping the horizontal distributions of EPBs, specially at the equatorial regions where ROTI failed to detect disturbances. Velocity estimates based on keograms from airglow data averaged 111 m/s, while TEC and ROTI index averaged 106 m/s and 107 m/s, respectively. Overall, TEC data presented better estimates of velocities due to the geometric and physical information, while ROTI offers statistical insights that often mask the natural propagation of EPBs.
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    Drift Velocity Estimation of Ionospheric Bubbles Using GNSS Observations
    (Advancing Earth and Space Sciences) Souza, Ana Lucia Christovam de; Camargo, Paulo de Oliveira; Muella, Marcio Tadeu de Assis Honorato; Tardelli‐Coelho, Flavia
    Equatorial plasma bubble (EPB) irregularities are large-scale plasma depleted structures that exist in the equatorial and low-latitude ionosphere. Thus, particularly in these regions, much attention must be given to the effects of the EPBs in the life critical applications based on global navigation satellite systems (GNSS). The study on the dynamics of plasma bubbles, particularly in the determination of their drift velocities, and their impact on ground-based augmentation system is of fundamental importance for civilian aviation. In this regard, we proposed a methodology to estimate the zonal drift velocities of the plasma bubble irregularities using slant total electron content (TEC) measurements derived from two spaced ground-based GNSS receivers. The experiments were performed with the purpose to evaluate if the drift velocities obtained using the methodology proposed in this study agree with the velocities deduced from all-sky imaging systems. The results revealed that the TEC-estimated mean eastward drift velocities were comparable with the values deduced from the airglow techniques, and with the results obtained from previous studies. Therefore, the methodology proposed in this work to infer the plasma bubble drift velocities seem to have the potential in future investigations to provide a new datasource in this field