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Simulate how solar wind dynamic pressure affects: magnetosphere-ionosphere coupling currents,

The Influence of Upstream Solar Wind on Thermospheric Flows at Jupiter Japheth N. Yates, Nick Achilleos, Patrick Guio. Simulate how solar wind dynamic pressure affects: magnetosphere-ionosphere coupling currents, momentum balance of atmospheric flows, System’s energy budget. Talk Outline.

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Simulate how solar wind dynamic pressure affects: magnetosphere-ionosphere coupling currents,

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  1. The Influence of Upstream Solar Wind on Thermospheric Flows at JupiterJapheth N. Yates, Nick Achilleos, Patrick Guio • Simulate how solar wind dynamic pressure affects: • magnetosphere-ionosphere coupling currents, • momentum balance of atmospheric flows, • System’s energy budget

  2. Talk Outline • Introduction • Model description • Plasma angular velocity profiles. • Results • M-I coupling currents • Momentum balance and thermospheric flows • Energy budget • Conclusions • Conclusion • Future work

  3. Introduction to model • Coupled magnetosphere, auroral conductivity and thermosphere model (Nichols and Cowley 2004, Cowley et al 2005, Grodent and Gerard 2001, Smith and Aylward 2008,9). • Used three magnetospheric configurations : compressed (A), average (B) and expanded (C). • Super-corotation of thermosphere. • Both thermosphere and magnetosphere sub-corotate to a greater degree with decreasing solar wind dynamic pressure. Yates et al (submitted to PSS)

  4. Results – Magnetosphere-ionosphere coupling currents • FAC densities peak at main auroral oval. • Increase in FACs and thus auroral intensity with decrease in solar wind pressure. • Compressed case (A) is interesting. • Model suggests auroral features at the open-closed field line boundary. • Oval location depends on Iρ at disc boundary. • Strong downward FAC due to large gradients in ΣP Yates et al (submitted to PSS)

  5. Results – Thermospheric momentum balance 1 • Low altitude: Momentum imbalance leads to poleward flow, advection arises to balance momentum which accelerates the polewards flow. Acceleration / advection seen by a comoving observer Yates et al (submitted to PSS)

  6. Results – Thermospheric momentum balance 2 Sub-corotational jet Super-corotational jet • High altitude: Momentum almost perfectly balanced, advection insignificant, thus flow is equatorwards. Yates et al (submitted to PSS)

  7. Results – Energy budget • Atmospheric power is sum of Joule heating and ion drag (Smith et al. 2007). • Power dissipated by Joule heating and ion drag increases by ~190% from case A to C. • Power used to accelerate magnetosphere towards corotation decreases slightly from case A-C. • Closed field atmospheric and magnetospheric power in Cowley et al. 2007 comparable (~80%) to compressed and average cases. Yates et al (submitted to PSS)

  8. Conclusions • Both thermosphere and magnetosphere sub-corotate to a greater degree with decreasing solar wind dynamic pressure. • Increase in auroral intensity with decrease in solar wind pressure. • Advection and ion drag play an important role in balancing momentum in the lower altitudes of the thermosphere (near the auroral ionization peak). • The power dissipated within the thermosphere by Joule heating and ion drag respectively increases by 190 % and 185 % between our compressed and expanded models.

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