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The growth of plasma convection in Saturn ’ s inner magnetosphere

The growth of plasma convection in Saturn ’ s inner magnetosphere X. Liu; T. W. Hill; R. A. Wolf; Y. Chen Physics & Astronomy Department, Rice University, Houston, TX. Outline Rice Convection Model (RCM) 3 plasma source models Simulation results comparison with observations.

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The growth of plasma convection in Saturn ’ s inner magnetosphere

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  1. The growth of plasma convection in Saturn’s inner magnetosphere X. Liu; T. W. Hill; R. A. Wolf; Y. Chen Physics & Astronomy Department, Rice University, Houston, TX MOP 2011

  2. Outline • Rice Convection Model (RCM) • 3 plasma source models • Simulation results • comparison with observations MOP 2011

  3. The Rice Convection Model (RCM) Described by Liu et al. [JGR, doi:10.1029/2010JA015859] Magnetosphere Coupling Ionosphere MOP 2011

  4. RCM setup • Saturn’s inner magnetosphere: 2<L<12 • Modeling region: 2<L<40 • (Boundary condition: L=2: ; L=40: ) • Ionospheric conductance: P = constant, H = 0 • Inner plasma source models: • J06 = [Johnson et al., Ap. J., 2006] • S10 E3 = [Smith et al., JGR, 2010, doi:10.1029/2009JA015184], “E3” version. • CJ10 = [Cassidy & Johnson, Icarus, 2010, doi:10.1016/j.icarus.2010.04.010] MOP 2011

  5. Comparison of 3 source models • Mass loading rate • Locations of charge-exchange /ionization cross-over, and of ionization peak. J06 24 kg/s CJ10 160 kg/s S10 E3 150 kg/s MOP 2011

  6. J06 24 kg/s Comparison of 3 source models (Ionization rate only) CJ10 160 kg/s S10 E3 150 kg/s MOP 2011

  7. Simulation results of J06 model MOP 2011

  8. Convection pattern at quasi steady state Slow, wide and dense outflow channels alternating with fast, narrow and tenuous inflow channels. MOP 2011

  9. Mass flux of J06 model MOP 2011

  10. Inflow longitudinal width ratio of J06 model [Observation data from Yi et al., JGR, 2010] MOP 2011

  11. Inflow and outflow channel velocities of J06 model [Observation data from Yi et al., JGR, 2010] MOP 2011

  12. Recall the mass loading rates of 3 source models J06 = 24 kg/s S10 E3 = 150 kg/s CJ10 = 160 kg/s What about scaling J06 model up to 150 kg/s mass loading rate? (Also scaling up Pwith the same ratioto confine the radial velocities) MOP 2011

  13. Model: J06*150/24 Global ionization: 150 kg/s Pedersen conductance: 0.3*150/24 S Model: J06 Global ionization: 24 kg/s Pedersen conductance: 0.3 S Scale up Inflow width ratio Inflow velocity Outflow velocity Mass flux MOP 2011

  14. Model: S10 E3 Global ionization: 150 kg/s Pedersen conductance: 0.3*150/24 S Inflow width ratio Inflow velocity Outflow velocity Mass flux MOP 2011

  15. Model: CJ10 Global ionization: 160 kg/s Pedersen conductance: 0.3*160/24 S Inflow width ratio Inflow velocity Outflow velocity Mass flux MOP 2011

  16. Conclusions • The radial distribution of plasma source plays a key role in plasma convection pattern. • The higher plasma mass loading rate can be compensated by higher ionospheric Pedersen conductance. • Simulations with more recent plasma source models are different from simulation with Johnson’s 06 model, and in disagreement with CAPS observations in some aspects. MOP 2011

  17. Thank you MOP 2011

  18. Supporting material MOP 2011

  19. Corotation lag of J06 model Observed result of corotation lag Simulated result of corotation lag MOP 2011

  20. Longitudinal width and radial velocity Faraday’s law for steady state: and w is the longitudinal width MOP 2011

  21. Test particles tracking of J06 model MOP 2011

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