Polar cap Artificial Auroras

It is well established that high-power high-frequency radio waves, when beamed into the F-layer ionosphere, accelerate electrons 1-2 orders of magnitude above thermal levels. These electrons collide with the neutral oxygen atoms and nitrogen molecules, which subsequently produce optical emissions identical to those in natural auroras. Artificial optical emissions are one of few methods available to directly detect energetic electrons in the ionosphere. The mechanism of acceleration remains under debate but there is evidence for turbulent upper-hybrid and Langmuir electrostatic waves. Artificial optical emissions have been observed at low latitudes (e.g. Arecibo in Puerto Rico), mid-latitudes (e.g. SURA in Russia), and at high latitudes (e.g. EISCAT in Norway and HAARP in Alaska). The electron accelerating mechanisms are sensitive to the magnetic field aspect angle to the pump beam, hence the need to reproduce the phenomenon at different latitudes. Here we report on the first attempt within the polar cap using the SPEAR facility on Svalbard, where the magnetic dip angle is only 8 degrees. Svalbard also has the unique situation of being under the cusp during the daytime whilst the ground is in total darkness during the winter months. In addition, Svalbard is the only location currently available where in-situ rocket measurements are possible within an artificial aurora. Plans for a future launch are discussed.