English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

. Spatial and temporal variation of the electron density in the atmosphere makes the ionosphere a difficult region to model. A major difficulty arises due to the incomplete geometrical coverage of the Global Navigation Satellite System (GNSS) for tomographic applications, making the ionospheric tomographic system an ill-conditioned problem. Although the tomographic system is ill-conditioned, several techniques have been developed to partially overcome the problem. There is great interest in using tomographic techniques for ionospheric imaging, because it allows describing the ionosphere in terms of electron density, which is an important parameter for studying the behavior of the physical processes that occur in the upper atmosphere. In Brazil, there are additional interests in the tomographic techniques, due to the peculiar characteristics of the ionosphere and of the geomagnetic field over the region. In this direction, methods of ionospheric tomographic reconstruction are presented and discussed in this review. Particular emphasis is given to the mathematical formulation from grid-based and function-based methods and are presented some of their main advantages and limitations. Keywords: TEC, Inverse Problem, Grid-Based Tomography, Function-Based Tomography, Ionospheric Imaging. RESUMO. A variacao espaco-temporal da densidade eletronica na atmosfera terrestre torna a ionosfera uma regiao de dificil modelagem. A principal dificuldade no imageamento da ionosfera com o GNSS (Global Navigation Satellite System ) e devido a geometria dos satelites, pois torna o sistema tomografico mal condicionado. Muito embora a geometria nao permita solucao direta do sistema, diversas tecnicas foram desenvolvidas para parcialmente superar tal problema. Ha grande interesse no uso de tecnicas de tomografia para o imageamento da ionosfera, pois permitem descrever a ionosfera ao nivel da densidade eletronica, sendo este um importante parâmetro para compreender os processos fisicos que ocorrem na alta atmosfera. No Brasil, existem interesses adicionais no imageamento ionosferico por meio de tecnicas tomograficas devido as caracteristicas peculiares da ionosfera e do campo geomagnetico sobre a regiao. Neste sentido, metodos utilizados para a reconstrucao tomografica da ionosfera sao apresentados e discutidos nesta revisao. Uma enfase especial e dada para a formulacao matematica dos metodos baseados em celulas e em funcoes, alem da apresentacao de algumas de suas principais vantagens e limitacoes. Palavras-chave: TEC, Problema Inverso, Tomografia Baseada em Celulas, Tomografia Baseada em Funcoes, Imageamento Ionosferico.

REVIEW OF TOMOGRAPHIC RECONSTRUCTION METHODS OF THE IONOSPHERE USING GNSS