Three dimensional ionospheric tomography based on flexible prior models.

摘要

An ionospheric reconstruction system will be presented that uses constraints from knowledge of ionospheric physics, to produce density solutions, consistent with available TEC measurement data. A major obstacle to implementing wide-scale ionospheric monitoring systems is the geometry of the ground based under-determined receiver and orbiting satellite measurement technique [76]. The resulting TEC data will contain limited information about variation of electron density with altitude [80]. Recently, a class of iterative algorithms that allow incorporating additional information, have been successfully used to provide solutions, without a great deal of additional computational complexity [68]. In addition, the nature of the solutions obtained is known to be close to an initial density solution model in the Kullback-Leibler sense. It is also known that current state of the art prior density models can only simulate a statistical mean ionosphere [3]. As a result, variations in ionospheric electron density will not be represented in these models. This thesis focus on a three-dimensional ionospheric density reconstruction system that uses a set of geometrical transformations to produce updated prior models, containing additional information not well represented in current state-of-the-art ionospheric density models. The updated priors are consequently used as initial solution models to a specific set of iterative algorithms that provide a spatially constrained density solution, consistent with the available data and our knowledge of ionospheric physics. The ultimate goal is to create a three-dimensional ionospheric electron density reconstruction system that would make it possible to generate real-time ionospheric maps. Such maps would be of significant utility in predicting and correcting the impact on radio waves of electron density gradients and irregularities.