Speaker
Description
Sporadic-E, thin metallic ion layers in the lower ionosphere compressed via neutral wind shears or externally imposed electric fields, pose considerable challenges for High Frequency (HF) radio propagation modelling. As their name suggests, these layers can appear to be quasi-stochastic, requiring both an abundance of metallic ions and a mechanism through which to compress them into thin, dense layers; as such, modelling Sporadic-E has been a persistent and long-standing challenge in ionospheric modelling. With physics-based models now beginning to develop the capability to capture the processes that produce these structures, we will here revisit empirical modelling of Sporadic-E at high latitudes and examine the capability of existing measurements to adequately constrain an empirical model. Using Radio Occultation (RO) measurements of these Sporadic-E layers, we have constructed a probabilistic model of Sporadic-E, its altitude, and its intensity over high latitude regions using neural networks. This presentation will provide an overview of this model and examine its performance via independent validation against both other RO and ground-based observations. We will furthermore examine the modelled behaviour and use the model to understand the climatological dynamics of Sporadic-E at high latitudes, which due to the additional role of magnetospherically-driven electric fields, include considerable dependence on the orientation of the high latitude electric fields and thereby the orientation and intensity of the solar wind magnetic field. Further discussion will explore how to implement this model within the existing Empirical Canadian High Arctic Ionospheric Model (E-CHAIM) and will explore the interplay between magnetospheric driving and thermospheric tides in controlling the convergence necessary to form Sporadic-E layers at high latitudes.
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