Technical report | A Description of a New Model of Sporadic E for JORN

Abstract

The morphology and physics of Sporadic E (Es) differs greatly to the normal physics of other ionospheric layers, so it is generally treated and modelled differently. The Es model within the Jindalee Operational Radar Network (JORN) is a real-time model with values based on sounder data, and has essentially remained unchanged since JORN's delivery in 2003 (despite years of progress in sounder processing). While this model can be used to manage the system when Es is present, systemic model difficulties must often be overcome by the manual intervention of experienced operators. This paper describes a new fully automatic data driven real-time model of the morphology of Es, and describes the associated expected propagation characteristic that should reduce the need for manual intervention. It has been adapted to work with JORN ionospheric sounder data in real time and tested with years of data. The models performance is characterised and discussed, and a probabilistic cumulative distribution function (CDF) is used to describe the probable value of the amplitude of Es. It includes an algorithm based on the available sounder data to determine the number of separate Es layers present in the data and a recommendation is made for the new model approach to Es be adopted in any future enhancement of JORN's model of Es propagation.

Executive Summary

Sporadic E (Es) morphology and physics differs greatly to the normal physics of other ionospheric layers, so it is generally treated and modelled very differently. The Es model within the Jindalee Operational Radar Network (JORN) is a real time model with values based on sounder data, and has essentially been unchanged since JORN’s delivery in 2003 (despite years of progress in sounder processing). While this model can be used to manage the system when Es is present, there are often systemic model difficulties that must be overcome by the manual intervention of experienced operators.

This paper describes a new fully automatic data driven real time model of the morphology of Es and the associated expected Es propagation characteristic that should make the need for manual intervention less common. It has been adapted to work with JORN ionospheric sounder data in real time and tested with years of data. Its performance has been characterised and is discussed.

This model produces a conventional and deterministic estimate of the height of the Es layer (hEs) used in the determination of Es path delay but allows this hEs estimate to have horizontal variations. This model also constructs a probabilistic cumulative distribution function (CDF) to describe the probable value of the amplitude of Es i.e. foEs, at any time or place in the Australian region. This model introduces the idea and possibility that two Es layers may be present at the same frequency and the same time but uses the available sounder data to make this determination.

It is recommended that this new model approach to sporadic E be adopted in any future enhancement of JORN’s model of Es propagation.