Browsing by Author "Valladares, Cesar"
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Item Open Access LISN network: tools for GPS data processing and managing(Instituto Geofísico del Perú, 2013) Espinoza, Juan C.; Valladares, CesarThe LISN network includes several GPS receivers installed around South America as a distributed observatory with the purpose of study the ionospheric phenomena. All of these receivers send data every 15 minutes to a central server located at Lima – Peru.Item Restricted Modeling ionospheric super‐fountain effect based on the coupled TIMEGCM‐SAMI3(American Geophysical Union, 2013-04-02) Lu, G.; Huba, J. D.; Valladares, CesarRecently, efforts have been undertaken to develop a coupled thermosphere‐ionosphere‐plasmasphere model based on two well‐established models, namely, the Thermosphere‐Ionosphere‐Mesosphere General Circulation Model (TIMEGCM) developed at the National Center for Atmospheric Research and the SAMI3 ionosphere model developed at the Naval Research Laboratory. This paper presents the first results from the coupled model on the investigation of a prompt penetration electric field (PPEF) event that took place on 9 November 2004. The coupled model eliminates two major upper boundary limitations of the stand‐alone TIMEGCM, e.g., the upper boundary height and the prescribed O+ fluxes at the upper boundary. It is found that the F‐layer peak height is raised above 800 km in response to the large PPEF. The O+ fluxes in the top ionosphere vary drastically during the course of the PPEF, with strong upward and downward fluxes with a magnitude greater than 109 cm−2 s−1 in localized regions. For the first time, the coupled model allows us to simulate and visualize the super‐fountain effect on a global scale. Future model development is also envisaged, including the implementation of a more realistic magnetic field model and a fully two‐way coupling between neutrals and ions.Item Restricted On the mutual relationship of the equatorial electrojet, TEC and scintillation in the Peruvian sector(American Geophysical Union, 2016-05-31) Khadka, Sovit M.; Valladares, Cesar; Pradipta, Rezy; Pacheco, Edgardo E.; Condor, PercyThis paper presents the interrelationship between the equatorial electrojet (EEJ) strength, Global Positioning System (GPS)‐derived total electron content (TEC), and postsunset scintillation from ground observations with the aim of finding reliable precursors of the occurrence of ionospheric irregularities. Mutual relationship studies provide a possible route to predict the occurrence of TEC fluctuation and scintillation in the ionosphere during the late afternoon and night respectively based on daytime measurement of the equatorial ionosphere. Data from ground based observations in the low latitudes of the west American longitude sector were examined during the 2008 solar minimum. We find a strong relationship exists between the noontime equatorial electrojet and GPS‐derived TEC distributions during the afternoon mediated by vertical E × B drift via the fountain effect, but there is little or no relationship with postsunset ionospheric scintillation.