Studies of low-latitude ionospheric irregularities during the periods of their low frequency of occurrence, and under quiet conditions / Estudo de irregularidades ionosféricas em períodos de baixa ocorrência em baixas latitudes sob condições calmas

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

This thesis research focalises a study of the mechanisms involved in the generation and evolution of the ionospheric plasma bubbles by means of experimental data and modeling. The experimental data were obtained by night airglow (OI630nm) imagers and Digisondes. The airglow allsky imager was located at São João do Cariri (7,5°S, 36,5°O, I=-20°), and the Digisondes were located at São Luís (2,6°S, 44,2°O, I=-2°), Fortaleza (3,9°S, 38,5°O, I=-11°) and Cachoeira Paulista (22,6°S, 45°O, I=-32°). This study was carried out during geomagnetically quiet days in order to minimize possible effects of magnetic storms on the generation of the plasma bubbles and, on the other hand, during the low season of bubble occurrence May to August during the years of 2001 and 2003 in order to more clearly detect the ionospheric parameters that deviated from the low season quiescent conditions contribute to the bubble generation. A 3-D model was developed to calculate the role of each ionospheric parameter (electron density heigh gradient, ionospheric upward velocity, ionospheric peak height etc.) in the generation of the bubble. The main conclusion of this computer simulation was that both the ionospheric bottom profile (electron density height gradient and bottom heigh) and upward velocity of the ionospheric plasma play a very important role in the bubble generation. The ionospheric height electron density profiles and the ionospheric Fregion upward velocity were obtained from the Digisonde at São Luís and were used as input data to the model program that simulates the bubble generation and evolution.

ASSUNTO(S)

instabilidades de plasma perturbações ionosféricas geofÍsica espacial space geophysics ionospheric plasma bubble bolhas ionosféricas ionosfera equatorial dinâmica da ionosfera equatorial ionosphere plasma instabilities ionospheric dynamics ionospheric disturbances space geophysics

ACESSO AO ARTIGO

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