Study of lower-hybrid cavities detected by the GEODESIC and OEDIPUS-C sounding rocket missions

Abstract

LHCs are structures in our upper ionosphere embedded within regions of strong plasma wave activity, referred to as auroral hiss. Heating inside these cavities (up to 50 times the ambient temperature) is contained within long, thin (rv 20 m across), cylindrically-shaped density depletions (up to tens of percent) aligned along the geomagnetic field. Trapped within these cavities are enhanced plasma waves, believed to be responsible for transversely accelerated ions (TAis). In this thesis we investigate a new depletion mechanism by which the particles are ejected transverse to the magnetic field , which predicts density enhancements at the cavity boundaries. These enhancement have been observed and cataloged for the first time as a part of this thesis. We find peak wave intensity does not occur at the cavity center but instead coincides with the maximum density gradient of the cavity. This result we hope will lead to a theory of the electromagnetic wave enhancements within LHCs. Using a new, high time-resolution instrument developed at the University of Calgary, we calculate the average energy of the TAis and find a moderate positive correlation between the heating region width and the maximum average energy reached by the TAis, suggesting that large LHCs dump more energy into the TAis.