IonMAP: Data assimilation system for three-dimensional imaging of the ionosphere in Brazil

Author(s)

Fabricio dos Santos Prol

• Document type: Doctoral Thesis
• Press: Presidente Prudente. 2019-02-11.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências e Tecnologia. Presidente Prudente
• Defense date: 2019-01-25
• Advisor: Paulo de Oliveira Camargo; Marcio Tadeu de Assis Muella

Abstract

Spatial and temporal variation of the electron density in the atmosphere make the ionosphere a difficult region to model. Several models were developed using Global Navigation Satellite System (GNSS) observations to represent the ionosphere by Vertical Total Electron Content (VTEC) maps. However, errors in the VTEC modeling occur due to the consideration of the ionosphere as a thin shell with constant height and the irrealistic mapping functions. In contrast, the ionosphere is a layer with 1000 km thickness. The electron density distribution with the altitude can be calculated using tomographic reconstruction techniques, which are based on slant TEC measurements to map the ionosphere in three dimensions. However, performing tomographic reconstructions using only TEC measurements has deficiencies in vertical representations of the ionosphere. To overcome this geometric deficiency, data assimilation can be performed including ionospheric profiles in the tomographic reconstruction. Data assimilation methods have been applied worldwide and a relevant peculiarity of the Brazilian region is the fact that some ionospheric dynamics over the region are not completely understood, as it is affected by the Equatorial Ionization Anomaly, ionospheric irregularities and strong vertical drifts in the evening pre-reverse period. In order to analyze the performance of data assimilation methods in the Brazilian area, this work aims to develop and evaluate a new method of data assimilation based on tomographic techniques to describe the ionosphere over Brazil using data from ionosonde, Radio-Occultation and ground-based GNSS. As a result, new understandings of the ionosphere were found, mainly related to the topside ionosphere and the single-frequency GNSS positioning. Furthermore, since the developed method provides a three-dimensional solution, it was possible to analyze the mitigation of the ionospheric delay using the slant TEC directly in the GNSS positioning. In addition to the good performance for describing TEC, the peak region and the topside, the developed method allowed to obtain representations of ionospheric plasma bubbles over the Brazilian area, which is a solution of great interest due to the strong impact of plasma bubbles in transionospheric signals. (AU)

• FAPESP's process: 15/15027-7 - Data assimilation for three-dimensional modelling of the ionosphere in Brazil
• Grantee: Fabricio dos Santos Prol
• Support Opportunities: Scholarships in Brazil - Doctorate