Radar studies of high latitude convection flows.
thesisposted on 19.11.2015, 09:18 by Mark. Burrage
Studies of the electrodynamics of the high latitude ionosphere contribute to the understanding of the coupling between the solar wind, magnetosphere and upper atmosphere. This thesis describes an experimental investigation of high latitude E-region convection flows carried out with the Sweden And Britain auroral Radar Experiment (SABRE). The ionospheric observations have been related to satellite measurements of the interplanetary medium and hence interpreted in terms of models of solar wind-magnetosphere-ionosphere coupling processes. A close relationship has been established between various solar wind parameters and the daily mean SABRE backscatter intensity, a quantity which is rarely employed in geophysical studies. Empirical IMF-dependent models of the convection flows observed by SABRE are developed and statistical studies of the occurrence time of the Harang discontinuity are presented. High spatial resolution, two dimensional maps of the ionospheric projection of the dayside merging region, for both polarities of the azimuthal component of the IMF, are obtained for the first time. Two examples of strong nightside convection flows observed throughout the SABRE latitude range indicate that the convection flows may penetrate at least as far south as 61.5° N, geomagnetic latitude, during strongly northward IMF. The study indicates that, in the long term, the structure of the solar wind can be deduced from the mean backscatter intensity measured by a SABRE radar. In addition, the azimuthal component of the IMF exherts a crucial influence on the convection flows observed by SABRE in the cusp region. This effect is not confined to the noon sector but is also apparent in the vicinity of the Harang discontinuity. In general, the convection pattern exhibits a dependence on the north-south component of the IMF consistent with established reconnection mechanisms. However, there is evidence that existing models are insufficient to explain the anomalous convection flows observed under conditions of strongly northward IMF.