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Xin Liu MOP 2011 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
Xin Liu MOP 2011 2
Outline
Rice Convection Model (RCM)
3 plasma source models
Simulation results
comparison with observations
Xin Liu MOP 2011 3
Magnetosphere
Ionosphere
|| sini i ij I �
||| | i e
eij j
B B
0
( )
E B
E
v 2
||
2
e e
ee s n
e
ej
B
J
BJ r v r v v
Coupling
new || : field-aligned Birkeland
current at magnetosphere
ej
|| : field-aligned Birkeland
current at ionosphere
ij
: electrostatic potential
: plasma velocityv
The Rice Convection Model (RCM)Described by Liu et al. [JGR, doi:10.1029/2010JA015859]
ds
B
Xin Liu MOP 2011 4
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]
0 0L
RCM setup
Xin Liu MOP 2011 5
S10 E3150 kg/s
CJ10 160 kg/s
J0624 kg/s
Comparison of 3 source models
Mass loading rate
Locations of charge-exchange
/ionization cross-over, and of
ionization peak.
Xin Liu MOP 2011 6
Comparison of 3 source models(Ionization rate only)
S10 E3150 kg/s
CJ10 160 kg/s
J0624 kg/s
Xin Liu MOP 2011 7
Simulation results of J06 model
Xin Liu MOP 2011 8
Convection pattern at quasi steady state
Slow, wide and dense outflow channels alternating with fast, narrow and tenuous inflow channels.
Xin Liu MOP 2011 9
Mass flux of J06 model
Xin Liu MOP 2011 10
Inflow longitudinal width ratio of J06 model
[Observation data from Yi et al., JGR, 2010]
Xin Liu MOP 2011 11
Inflow and outflow channel velocities of J06 model
[Observation data from Yi et al., JGR, 2010]
Xin Liu MOP 2011 12
Recall the mass loading rates of 3 source models
J06 = 24 kg/sS10 E3 = 150 kg/sCJ10 = 160 kg/s
What about scaling J06 model up to 150 kg/s mass loading rate?(Also scaling up P with the same ratio to confine the radial velocities)
Xin Liu MOP 2011 13
Model: J06Global ionization: 24 kg/s
Pedersen conductance: 0.3 S
Model: J06*150/24Global ionization: 150 kg/s
Pedersen conductance: 0.3*150/24 S
Mass flux
Outflow velocity
Inflow velocity
Inflow width ratio
Scale up
Xin Liu MOP 2011 14
Model: S10 E3Global ionization: 150 kg/s
Pedersen conductance: 0.3*150/24 S
Mass fluxOutflow velocityInflow velocityInflow width ratio
Xin Liu MOP 2011 15
Model: CJ10Global ionization: 160 kg/s
Pedersen conductance: 0.3*160/24 S
Mass fluxOutflow velocityInflow velocityInflow width ratio
Xin Liu 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.
Xin Liu MOP 2011 17
Thank you
Xin Liu MOP 2011 18
Supporting material
Xin Liu MOP 2011 19
Observed result of corotation lag Simulated result of corotation lag
Corotation lag of J06 model
Xin Liu MOP 2011 20
Longitudinal width and radial velocity
0t
B
E
Faraday’s law for steady state:
inflow
outflow
out
in
w
w
v
v
0 E v B
and
w is the longitudinal width
Xin Liu MOP 2011 21
Test particles tracking of J06 model