Title: Ramifications of intermediate-scale ionospheric structure for tomographic reconstruction using two-dimensional simulation
Abstract:
Global observation of the GPS satellite constellation for ionospheric diagnostics is a worldwide activity driven by both practical and scientific objectives. Diagnostic methods exploit an induced frequencydependent phase change, which is proportional to the path-integrated electron density (TEC). However, intermediate-scale structure causes a stochastic modulation of the GPS signals (scintillation), which is a nuisance for data assimilation. Indeed, sufficiently strong propagation disturbances degrade TEC and ultimately disrupt GPS operations altogether.
A two-dimensional propagation model is used to explore the rami…fications of intermediate scale structure on TEC data assimilation and, particularly tomographic reconstruction. Although twodimensional models confine structure to a planar region, the results are relevant, with caveats, to propagation through highly anisotropic ionospheric structures. In-plane propagation from a source to an array of receivers is amenable to reconstruction with tomographic filtered back-projection algorithms.
The angle-dependent Fourier decomposition of the array signal phase identifies a spectral slice. The signals from which the phase is derived are generated with an oblique forward propagation procedure developed by Costa and Basu. Under weak-scatter conditions the signal phase is proportional to the ray path integral.
The results demonstrate the rami…fications of diffractive distortion of path-integrated phase as well as unresolved stochastic structure. Anisotropic structure that subtends the disturbed region complicates the reconstruction procedures, particularly under strong scatter conditions. The utility of backpropagation to mitigate propagation disturbances will also be explored.