Extreme Vertical Winds in the Thermosphere: Polar cap vs. Auroral Oval
Open Session on Magnetospheric, Ionospheric and Solar-Terrestrial physics
Amy Ronksley
Dr Anasuya Aruliah
Thermospheric vertical winds are generally small magnitude, a characteristic of the thermosphere's strong convective stability, therefore, they are thought to make an insignificant impact on the aeronomy of the region. However at high latitudes near the auroral oval Joule and particle heating can drive extremely large magnitude winds, displacing species from equilibrium, altering thermospheric density and chemistry thus shifting the heights of the E and F regions, i.e., a significant impact on the thermosphere.

University College London's (UCLs) extensive Fabry Perot Interferometer (FPI) database has been exploited to investigate the behavior of vertical winds at two different high latitude locations: Kiruna in the auroral oval and Svalbard in the polar cap. Histograms are created which quantify the frequency of extreme vertical wind events and exhibit the general behavior of the winds. By further binning the data by other geomagnetic indices, we find under what conditions these extreme events occur. The behavior of the wind is very different at the two sites. A relationship between the vertical wind and proximity to the auroral oval is found, as well as a potential signature of the cusp. The Svalbard data exhibits an excess of extreme upwelling events not evident in the Kiruna data. These are termed 'black swan' events, as they do not comply with the known auroral physics which explains the rest of the data. Possible explanations for this phenomena are investigated.
16:30 - 18:00