Stochastic TEC Structure Characterization

摘要

The global navigation satellite systems provide high-quality total electron content (TEC) measurements that are used routinely for ionospheric diagnostics. Large-scale TEC structure is a critical input for maintaining global ionospheric models. However, residual stochastic TEC structure is typically discarded as a phase-scintillation-induced error. In this paper we show that the phase-scintillation errors are a negligibly small fraction of the stochastic TEC component for most global navigation satellite system operating conditions. With three-frequency GPS satellite measurements, two independent TEC measurements can be compared to bound the scintillation-induced errors. Data analysis and simulations show that scintillation-induced errors are a small fraction of one TEC unit as long as the lower contributing frequency S4 index is less than 0.5. To the extent that scintillation-induced errors are negligible, spectral analysis of stochastic TEC provides a direct measure of path-integrated structure. Irregularity parameter estimation can be used to estimate power law parameters, which in turn can be interpreted with a new global ionospheric structure model.We present a summary analysis of month-long series of continuous measurements at Poker Flat, Alaska. The analysis confirms the generally accepted single power law model for high-latitude structure. A small fraction of the measurements indicate an outer-scale transition at approximately 17 km. The general pattern of the structure occurrence is consistent with auroral-zone activity.