 |
Center for Nonlinear Studies |
In this talk, I will overview space physics problems that I have been working on as a PhD student in the SuperDARN radar group at the University of Saskatchewan, Canada. I first will introduce several space science missions, experiments and techniques aimed to study the ionosphere. I will emphasize how these missions/instruments can help us in addressing some long-standing problems in space physics. I will then cover basics of plasma instabilities in the Earth’s ionosphere and explain how small-scale, meter and decameter, irregularities excited through these instabilities are used for ionospheric research with coherent radars such as SuperDARN. Next, I will talk about rather exotic auroral phenomenon, the so-called "theta-aurora" or polar cap arcs, an exclusively polar cap phenomenon in contrast to the more typical auroral arcs that reside inside the auroral oval. Polar cap arcs occur when the Bz component of the interplanetary magnetic field (IMF) is northward so that coupling between the solar wind and the magnetosphere is rather weak. Results on the plasma flows around polar cap arcs and how the arcs modify an overall high-latitude convection pattern will be presented and discussed along with the magnetotail sources of this high-latitude aurora. I will then move to another unresolved question relevant to positive IMF Bz conditions, an overall large-scale convection pattern. I will show that, for strong positive Bz, two additional convection cells are formed on the dayside with sunward flow along the noon-midnight magnetic meridian. I will present SuperDARN data demonstrating interhemispheric asymmetry in the patterns with faster flows in the summer (sunlit) ionosphere. When the IMF Bz component turns negative, coupling between the solar wind and the magnetosphere becomes efficient so that the excessive energy accumulates in the magnetotail and eventually can be suddenly released into the high-latitude ionosphere which leads to a chain of processes known as a substorm. Substorm is one of the central and unsolved problems in space physics. I will show some results of our statistical analysis of the substorm occurrence rates, which can help us to understand a mechanism of substorm triggering, an important component in developing a viable substorm theory and predictions.
Host: Gian Luca Delzanno, T-5