Revealing Particle Acceleration Physics During Substorms With Auroral Kilometric Radiation

The Earth's magnetosphere is the region of space close to Earth dominated by Earth's magnetic field. It is not empty, but contains plasma (charged particles) trapped by the magnetic field. In certain regions of the magnetosphere the trapped plasma can produce radio waves as the particles are accelerated along the Earth's magnetic field lines, known as Auroral Kilometric Radiation (AKR). This radio emission can be measured using instruments on board spacecraft, and can give us important information about the particle acceleration. The magnetosphere is highly dynamic and often undergoes a type of global reconfiguration know as a geomagnetic substorm. The onset of a substorm produces some of the most dynamic and spectacular aurora as energy is rapidly transferred from the magnetosphere to the upper atmosphere. In this project we will use observations of AKR made by the Wind spacecraft together with images of the aurora from Lapland to investigate the triggering of substorms and what happens in the minutes around substorm onset. There are several steps to the auroral dynamics in the lead up to a substorm, including the growth of a wave-like movement known as auroral beads. We will measure the energy of the accelerated particles producing the beads to learn more about the mechanism producing the acceleration, and we will investigate changes in the AKR through the different stages of the auroral dynamics. In particular, we will investigate a possible precursor signature of substorms which we found in a previous study of AKR, which could give important clues about the processes which make a substorm begin.