Navegando por Autor "Tsali-Brown, Vera Yesutor"

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    Ionospheric storm due to solar Coronal mass ejection in September 2017 over the Brazilian and African longitudes
    (Elsevier) Fagundes, Paulo Roberto; Tsali-Brown, Vera Yesutor; Pillat, Valdir Gil; Arcanjo, Mateus de Oliveira; Venkatesh, Kavutarapu; Habarulema, John Bosco; Bolzan, Maurício José Alves; Jesusm Rodolfo F. de; Abreu, Alessandro José de; Tardelli, Alexandre; Vieira, Francisco; Denardini, Clezio Marcos
    Coronal mass ejection (CME) occurs when there is an abrupt release of a large amount of solar plasma, and this cloud of plasma released by the Sun has an intrinsic magnetic field. In addition, CMEs often follow solar flares (SF). The CME cloud travels outward from the Sun to the interplanetary medium and eventually hits the Earth’s system. One of the most significant aspects of space weather is the ionospheric response due to SF or CME. The direction of the interplanetary magnetic field, solar wind speed, and the number of particles are relevant parameters of the CME when it hits the Earth’s system. A geomagnetic storm is most geo-efficient when the plasma cloud has an interplanetary magnetic field southward and it is accompanied by an increase in the solar wind speed and particle number density. We investigated the ionospheric response (F-region) in the Brazilian and African sectors during a geomagnetic storm event on September 07–10, 2017, using magnetometer and GPS-TEC networks data. Positive ionospheric disturbances are observed in the VTEC during the disturbed period (September 07–08, 2017) over the Brazilian and African sectors. Also, two latitudinal chains of GPS-TEC stations from the equatorial region to low latitudes in the East and West Brazilian sectors and another chain in the East African sector are used to investigate the storm time behavior of the equatorial ionization anomaly (EIA). We noted that the EIA was disturbed in the American and African sectors during the main phase of the geomagnetic storm. Also, the Brazilian sector was more disturbed than the African sector.
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    Momentum flux characteristics of vertically propagating gravity waves
    (European Geosciences Union) Nyassor, Prosper Kwamla; Wrasse, Cristiano Max; Paulino, Igo; Yigit, Erdal; Tsali-Brown, Vera Yesutor; Buriti, Ricardo Arlen; Figueiredo, Cosme Alexandre Oliveira Barros; Giongo, Gabriel Augusto; Egito, Fabio; Adebayo, Oluwasegun Micheal; Takahashi, Hisao; Gobbi, Delano
    Momentum flux and propagation dynamics of two vertically propagating atmospheric gravity waves (GWs) are studied using observations at São João do Cariri (7.40° S, 36.31° W), Brazil, from co-located pho- tometer, all-sky imager, and meteor radar instruments. Time series of the atomic oxygen green line (OI 557.7 nm), molecular oxygen (O2 (0–1)), sodium D-line (NaD), and hydroxyl (OH (6–2)) airglow intensity variations mea- sured by the photometer were used to investigate the vertical characteristics and vertical phase progression of the GWs with similar (± 10 % of the error margin) or nearly the same (± 5 % of the error margin) period across these emission layers. The horizontal parameters of the same GWs were determined from the OH airglow im- ages, whereas the intrinsic parameters of the horizontal and vertical components of the GWs were estimated with the aid of the observed winds. Using the phase of the GWs at each emission layer, the characteristics of the phase progression exhibited near-vertical propagation under a duct background propagation condition. This indicates that the duct contributes significantly to the observed near-vertical phase propagation. The GW mo- mentum flux and potential energy were estimated using the rotational temperatures of OH and O2, revealing that the time series of momentum fluxes and potential energies are higher in the O2 emission band than in the OH band, indicating a transfer of momentum and energy across OH to the O2 altitude. These results reveal the effect of a duct on vertically propagating GWs and the associated momentum flux and potential energy transfer from the lower to the upper altitudes in the mesosphere.