Abstract Ionospheric electron density affects trans-ionospheric radio waves. Estimating electron density, therefore, is vital to mitigate the effect of ionosphere on radio waves. As a result, different methods have been applied to estimate ionospheric electron density from integrated measurements of ground-based GPS (Global Positioning System) receivers recently installed in East-Africa.
To augment such efforts, ionospheric electron density has been estimated from Radio Occultation (RO) total electron content data measured by LEO (Low Earth Orbit) satellites. Abel inversion onion peeling algorithm then is used to retrieve electron density profiles from the calibrated data. The reconstructed electron density profiles have been validated by running the standard ionospheric empirical model (International Reference Ionosphere, IRI-2007) at time and locations that RO electron density profiles are obtained. The results show well agreement between the Abel inversion and IRI-2007 electron density profiles, for both bottom and topside ionosphere. Also, F2 peak density heights from Abel inversion and IRI-2007 have shown well agreement. However, significant discrepancy has been detected around the height of the F2 peak density.
Table of Contents
1. Introduction
Objective:
2. Methodology
3. Results and discussion
Observation:
4. Conclusion and recommendation
Conclusion
Recommendations
Acknowledgements
Research Objectives and Key Topics
The primary objective of this research is to estimate ionospheric electron density profiles by applying the Abel inversion onion peeling algorithm to radio occultation (RO) Total Electron Content (TEC) data collected by COSMIC satellites. Furthermore, the study aims to validate the accuracy of these retrieved profiles by comparing them with electron density profiles generated by the standard International Reference Ionosphere (IRI-2007) model.
- Retrieval of electron density profiles using the Abel inversion method.
- Application of the onion peeling algorithm to COSMIC radio occultation data.
- Validation of retrieved profiles against the IRI-2007 empirical model.
- Comparative statistical analysis of peak electron density (NmF2) and peak height (hmF2).
Excerpt from the Book
1. Introduction
Ionosphere is the ionized part of the Earth’s upper atmosphere which contains free electrons and positive ions. It is formed when solar radiation strikes the upper atmosphere in such a way that the incoming radiation with sufficient energy takes away electrons from the neutral atom and hence ionized medium is formed. The electrons formed as a result of the ionization process in general and Total Electron Content (TEC) in particular are the main characterizing features of the ionosphere. TEC is defined as the integration of the free electron distribution in a 1m^2 column along the signal path from the satellite to the receiver. The variation of these parameters describes the variations of the ionosphere. Some of the determinants of ionosphere variation are solar radiation variation, thermospheric wind, deposition of energetic particles at higher latitudes and variation in neutral composition of the atmosphere [2].
The variation of the ionosphere affects trans-ionospheric radio wave users, for example, communication and GPS (Global Positioning System) applications such as positioning and navigation. A proper way of understanding the ionospheric variability can help us to use the appropriate signals that are used for communication purposes.
Summary of Chapters
1. Introduction: Defines the ionosphere and the significance of TEC, while outlining the necessity of radio occultation techniques for ionospheric monitoring and the specific objectives of this study.
2. Methodology: Details the theoretical basis of the Abel inversion onion peeling algorithm and the procedure for converting slant TEC data into vertical electron density profiles.
3. Results and discussion: Presents the retrieved electron density profiles, discusses observations regarding altitude variations, and evaluates the results against the IRI-2007 model through statistical analysis.
4. Conclusion and recommendation: Summarizes the study's findings regarding the agreement between models and provides suggestions for future research, such as accounting for horizontal TEC variations.
Keywords
Abel inversion, electron density, radio occultation, total electron content, COSMIC, ionosphere, IRI-2007, onion peeling algorithm, NmF2, hmF2, ionospheric modeling, GNSS, GPS, atmospheric science, remote sensing
Frequently Asked Questions
What is the core focus of this research?
The research focuses on retrieving vertical electron density profiles of the ionosphere using radio occultation data obtained from COSMIC satellites and the Abel inversion technique.
What are the central themes discussed in this work?
The central themes include ionospheric variability, the application of Abel inversion algorithms, and the validation of satellite-derived data against established empirical models like the International Reference Ionosphere (IRI-2007).
What is the primary objective of this study?
The primary goal is to demonstrate the feasibility of using the onion peeling algorithm on COSMIC radio occultation data to estimate electron density and to verify the reliability of this method compared to the IRI-2007 standard model.
Which scientific method is primarily employed?
The study employs the Abel inversion onion peeling algorithm, which is a mathematical approach to retrieve spatial distribution data from integrated line-of-sight measurements.
What is addressed in the main body of the work?
The main body covers the theoretical formulation of the inversion method, the discretization of ionospheric layers, the data extraction process from netCDF files, and the subsequent analysis of electron density profiles.
Which keywords characterize this paper?
Key terms include Abel inversion, electron density, radio occultation, total electron content (TEC), and COSMIC satellites.
How does the Abel inversion method handle the ionosphere?
The method assumes spherical symmetry, treating the ionosphere as a series of layers with uniform electron density, allowing for an iterative calculation from the top layer down to the bottom.
Why are there negative values in some electron density profiles?
Negative values are an inherent limitation of the inversion technique implemented, occurring primarily in the lower regions due to the mathematical approximations used in the spherical symmetry assumption.
How do the results compare to the IRI-2007 model?
The retrieved peak heights (hmF2) show good agreement with the IRI-2007 model, suggesting the method is consistent for height estimation, while significant discrepancies remain in peak electron density (NmF2) values.
What recommendations are made for future improvements?
It is recommended to incorporate horizontal TEC variations to improve accuracy and to extend the study to account for TEC values above the current LEO satellite orbit altitude.
- Arbeit zitieren
- Bizuayehu Adisie Beyene (Autor:in), 2016, Estimating Electron Density of the Ionosphere from Radio Occultation TEC Data using Abel Inversion, München, GRIN Verlag, https://www.grin.com/document/323503
