Titan’s Thermospheric Response to Various Plasma Environments Joseph H. Westlake Doctoral Candidate The University of Texas at San Antonio Southwest Research Institute [email protected][email protected]J. H. Westlake, J. M. Bell, J. H. Waite, R. E. Johnson, J. G. Luhmann, K. E. Mandt, B. A. Magee, and A. M. Rymer
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Titan’s Thermospheric Response to Various Plasma Environments
Titan’s Thermospheric Response to Various Plasma Environments. J. H. Westlake, J. M. Bell, J. H. Waite, R. E. Johnson, J. G. Luhmann , K . E. Mandt , B. A. Magee, and A. M. Rymer. - PowerPoint PPT Presentation
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Titan’s Thermospheric Response to Various Plasma
Environments
Joseph H. Westlake Doctoral Candidate
The University of Texas at San Antonio Southwest Research Institute
• The mean scale height method was used on each flyby individually
Plasma Sheet Average: 144.7 K
Lobe Average: 118.2 K
Δ = 26.5 K
Westlake et al. (In Review)Joseph Westlake (UTSA/SwRI) – [email protected]
Temporal Variations
Results:Similarly oriented flybys which are separated by one Titan day (~16
Earth days) show large effective temperature deviations.
• The difference in observed effective temperature may deviate more in a temporal fashion than in a spatial fashion
• Flybys occurring one Titan day apart with nearly identical trajectories and solar conditions
ΔTEff = 29 KΔTEff = 20 K
Westlake et al. (In Review)Joseph Westlake (UTSA/SwRI) – [email protected]
Time Scales?• INMS data indicates
that Titan responds on a timescale of less than one Titan day.
Titan’s thermosphere seems to respond to plasma heating on a timescale of about 10 Earth Days
Thermal Time Constant (Earth Days)
)()()(rQrTr tot
Bell et al. (Submitted)Joseph Westlake (UTSA/SwRI) – [email protected]
Pulse StartEstimated Recovery
TimePulse Stop
Simulating Titan’s Plasma Response• Using the T-GITM model we
simulate a ½ Titan day heating pulse.
(A) Thermal response with diurnal portion removed
(B) Actual thermal response(C) Altitude map of thermal
response
Simulated Titan Days
Bell et al. (Submitted)Joseph Westlake (UTSA/SwRI) – [email protected]
Results• The relaxation time is
roughly 10 Earth Days.• Tends to most affect the
region above 1000 km.
Conclusions
• During the solar minimum conditions prevailing during the Cassini tour, the plasma interaction plays a significant role in determining the thermal structure of the upper atmosphere and, in certain cases, may over-ride the expected solar-driven diurnal variation in temperatures in the upper atmosphere.
• Temperatures are observed to be enhanced by 29 K on average when Titan is within the plasma sheet over when it is within the lobe regions.
• Titan’s thermosphere responds to plasma forcing on timescales less than one Titan day (~10 Earth days)