Mr. James Waters

University of Southampton, UK

Multi-decadal observations of auroral kilometric radiation with the Wind spacecraft and its variability during substorms

Abstract : Auroral Kilometric Radiation (AKR) is circularly-polarised radio emission that originates from particle acceleration regions along magnetic field lines that coincide with discrete auroral arcs and geomagnetic activity. For decades, radio astronomy instruments aboard various spacecraft have been used to derive the source directions and flux densities of radio emissions of various origin. The Wind spacecraft has been in operation for 25 years and its flight characteristics (spin-stabilised, orthogonal antennae) have been considered in the development of techniques involving direction-finding and polarimetry of a radio source. Such techniques allow for the angular coordinates, the angular radius and the Stokes (flux and polarisation) parameters to be retrieved, and have been used previously to study solar radio emissions under assumptions of the source polarisation. Here, a technique that accounts for partial polarisation in an extended radio source is developed that will return source parameters for not only AKR but other sources, although there are limitations to the automation of the analysis that must be examined. With polarisation considered, the long timespan of Wind data can produce a utile dataset. Statistical properties of AKR can be examined, with the extent of local time sampling of Wind bolstering previous studies. The previously observed correlation between morphological changes in the source region and magnetospheric substorm onset can be studied further, and lists of substorm phase timings can be used to examine the general variability during these events.