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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. - PowerPoint PPT Presentation
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The Influence of Upstream Solar Wind on Thermospheric Flows at JupiterJapheth N. Yates, Nick Achilleos, Patrick Guio
Simulate how solar wind dynamic pressure affects: 1. magnetosphere-ionosphere coupling currents, 2. momentum balance of atmospheric flows, 3. System’s energy budget
Talk Outline
• Introductioni. Model description
ii. Plasma angular velocity profiles.
• Resultsi. M-I coupling currents
ii. Momentum balance and thermospheric flows
iii. Energy budget
• Conclusionsi. Conclusion
ii. Future work2
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.
3
Yates et al (submitted to PSS)
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 4
Yates et al (submitted to PSS)
Results – Thermospheric momentum balance 1
• Low altitude: Momentum imbalance leads to poleward flow, advection arises to balance momentum which accelerates the polewards flow. 5
Yates et al (submitted to PSS)
Acceleration / advection seen by a comoving observer
Results – Thermospheric momentum balance 2
• High altitude: Momentum almost perfectly balanced, advection insignificant, thus flow is equatorwards.
6
Yates et al (submitted to PSS)
Sub-corotational jet
Super-corotational jet
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. 7
Yates et al (submitted to PSS)
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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