First step towards tiger frequency management: A ray tracing exploration using both IRI and IGRF models

Abstract

Now that a recent addition to the southern hemisphere Super Dual Auroral Radar Network (SuperDARN) - The Tasman International Geospace Environment Radar (TIGER) - has become operational, real-time frequency management and coordinates registration of both back- and ground-scattered echoes are needed. Currently, and certainly in the near future, TIGER will operate like a high-frequency direction finding, single-site location instrument given that no other SuperDARN instrument currently overlaps its field of view. Ray tracing can be used initially to devise an optimum choice of operating frequencies for maximum coverage and to locate geographically (or geomagnetically) the backscattering regions. For convenience, we relied on the International Reference Ionosphere (IRI) and Geomagnetic Reference Field models (IGRF) for the electron density profile and geomagnetic field as both models could easily be implemented in the ray-tracing code. Collisions were neglected. We also assumed that the radar echoes would mainly return from regions of the ionosphere where rays are nearly perpendicular to the local geomagnetic field. Throughout the study, we considered the magnetic aspect angle condition, | sin −1 ( K·B /kB )|≤05°, to be a necessary (yet insuffiient) condition for backscatter resulting from field-aligned irregularities. We retained as potential backscatter centres all points along the rays where the condition is fulfilled. Although our approach does not encompass all types of irregularities susceptible to produce significant radar returns and completely ignores the geographic distribution of irregularities by assuming their omnipresence, it provides a starting point for the real-time frequency management of the TIGER radar.