Study of the equatorial ionosphere electrodynamics during the solar maximum period (1999-2002) / Estudo da eletrodinâmica da iosfera equatorial durante o périodo de máxima atividade solar (1999-2002)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

This thesis presents the results from the study of the equatorial ionosphere electrodynamics during the solar maximum period (1999-2002). For this study a new approach in the analysis of the 50 MHz coherent back-scatter radar data based on Gaussians fitting of the Doppler spectra was developed. The technique is presented, demonstrated and validated with test and experimental data. The variability of the 3-meter irregularities of the equatorial electrojet is studied during quiet and disturbed auroral activity to demonstrate the diversity of the equatorial electrojet phenomenology and its variability in the Brazilian sector. This study had given us a good idea of some important aspects of the equatorial electrojet during quiet and disturbed conditions. An analysis of intensity and format of the equatorial electrojet based on its parameterization was carried on in two steps. First step of analysis comprehended the data set covering the period from January 23 to February 15, 2001. This step confirmed the initial expectations and was used to improve the technique of parameterizations. Second step was an extension of the preliminary study using the 2002 data set covering the whole year. In this step, the data set was separated according to the magnetic activity and season. The second step analysis confirmed the presence of an East-West power asymmetry in the back-scatter radar signal in the Brazilian sector, as seen in the first step. Besides, some daily and seasonal characteristics of this power asymmetry are presented. The appearance of a scattering region after sunset during magnetically quiet conditions around the summer solstice is also shown. The Gaussian fitting applied to the spectrograms yielded the Doppler frequencies of the plasma irregularities that were used to calculate the polarization and the zonal electric fields at various electrojet heights. This study included an analysis of the variability of these fields in height, season and according the geometry of the sounding. Moreover, the results from our calculations were compared to the others values of electric fields from the equatorial electrojet available in the scientific literature. From this study we could confirm the presence of an asymmetry in the frequencies/velocities type 2, similar to the power asymmetry observed in the earlier studies.

ASSUNTO(S)

aeronomia equatorial electrojet coherent radar aeronomy electric fields radar echoes campos elétricos região e e-region eletrojato equatorial radar coerente ecos de radares

ACESSO AO ARTIGO

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