Monday

Mesoscale density structures in the polar regions are poorly represented by empirical atmospheric models used in satellite orbit determination. In particular they do not allow for heating from electrical currents generated by the solar wind-magnetospheric dynamo in the auroral regions. Heating causes upwelling of the denser air. On either side of a heating region there is downwelling as the atmosphere relaxes back to a normal state. Physics-based models are better able to represent the meso-scale structures, but are far too slow to be useful for near-instantaneous orbit prediction. Two nights are presented here as case studies to indicate the size of vertical winds and the horizontal extent of up and downwelling regions for geomagnetically quiet and active conditions. Long-lived up/downwellings have been observed by Fabry-Perot Interferometers measuring the vertical winds at Svalbard. Simultaneous measurements by the EISCAT Svalbard Radar have shown electron density enhancements and, in particular, field-aligned plasma flow driven by the neutral winds, consistent with large up/downwelling. We also used the UCL Coupled Middle Atmosphere Thermosphere (CMAT2) model to estimate the changes in density from a localised heat source, representative of auroral plasma flows. Finally we present initial results from the PHOENIX CubeSat which was one of the QB50 constellation of CubeSats launched in the summer of 2017. PHOENIX carries a miniaturised mass spectrometer, with the aim to provide the first in-situ mass spectrometer measurements since the two Dynamics Explorer spacecraft in the late 1970s- early 1980s.