Summary
Current research utilises the recently installed Southern Hemisphere Imaging Riometer (SHIRE) located at Australia’s Davis Antarctic station to study riometer signatures associated with cusp-latitude magnetic impulse events (MIE’s) detected in co-located fluxgate magnetometer data. Such observations enable further refinement of the characterisation of MIE’s by observing the spatial scale, morphology and dynamics of associated patches of locally enhanced Cosmic Noise Absorption (CNA). The multiple narrow beams which comprise the field-of-view of an imaging riometer allow us to obtain two-dimensional images of the localised absorption patches as they evolve over time, facilitating study of the structure and motion of MIE-associated absorption events. Of those dayside MIE’s with a detectable riometer signature, two distinct morphologies have emerged. The first of these has many characteristics of the morning sector absorption spikes reported by Stauning and Rosenberg (1996), yet with a previously unreported spatial and temporal bipolarity in the riometer signature. The second and more common signature observed in association with magnetic impulses is a widespread increase in absorption of spatial scale larger than the 200x200 km 2 field-of-view of the imaging riometer, but with generally smaller amplitude and consistent antisunward and magnetic poleward convection. In this paper we present two case studies illustrating both types of events.