Aruliah, A; (2018) Auroral thermosphere density study. UCL BEAMS: London, UK.

Preview

Text Density-FinalReport-Aruliah-final2-2018.pdf Download (2MB) | Preview

Abstract

Atmospheric drag is the 2nd largest perturbation on satellite orbits, after the gravitational force of an oblate Earth. Atmospheric drag occurs where the satellite enters the top layer of the Earth’s atmosphere, the thermosphere, which means an altitude below around 300 km at solar minimum, and around 800 km at solar maximum. The concern of our project is the “lumpiness” of thermospheric density. In particular, mesoscale density structures in the polar regions are poorly represented by empirical atmospheric models used in satellite orbit determination. 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 which can be observed by Fabry-Perot Interferometers measuring the vertical winds. 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 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. We also use 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 Dynamics Explorer in the early 1980s. The proposed objectives were: 1) Set up the FPIs to be calibrated and ready for the experiment, and in a fit state to continue monitoring the upper thermosphere and extending the dataset of auroral measurements to provide context for the experiment. 2) Carry out a 24 hour experiment using the network of Fabry-Perot Interferometers (FPIs) with the EISCAT and SuperDARN radars to provide a case study to investigate the density variation of the upper thermosphere in the auroral and polar cap region. 3) Undertake a modelling study using the UCL CMAT2 global circulation model to investigate the contribution of frictional heating in the auroral zones to the density variation. 4) Prepare a set of CMAT2 model simulations to be used to estimate the size of orbit perturbations and to compare with conventional satellite drag models. These objectives were all achieved and highlights are listed below. • Field campaign trip to the KEOPS and Sodankylä FPI sites 9-27 January 2018 • Dr Ian McWhirter consultancy for instrumental work and maintenance for the field trip • EISCAT mainland and ESR radar experiments: 1. 16UT on 28 Jan 2017 – 04UT on 29 Jan 2017 (ESR CP2 and 2. 16UT on 30 Jan 2017 – 04UT on 31 Jan 2017 • Related activities: 3 invited talks, 3 talks, 1 poster and 2 4th year undergraduate projects (see reference list) • Extended the grant period by 4 months to 14 April 2018, in order to include the first of 2 QB50 Incoherent Scatter World Day periods (January 2018)

Download activity - last month

Export as JSONXMLCSV

Download activity - last 12 months

Export as CSVXMLJSON

Downloads by country - last 12 months

Export as CSVJSONXML

Archive Staff Only

View Item