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Introduction The Io Plasma Torus in 2 Minutes The Role of Hot electrons Longitudinal Variations

The Post-Cassini View of the Io Plasma Torus Andrew Steffl, Adam Shinn (Southwest Research Institute – Boulder) With thanks to Fran Bagenal, Peter Delamere, Nick Schneider and the UVIS team MOP 2011 , Boston. Introduction. IPT in 2 minutes. Hot Electrons. Longitudinal Variations.

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Introduction The Io Plasma Torus in 2 Minutes The Role of Hot electrons Longitudinal Variations

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  1. The Post-Cassini View of the Io Plasma TorusAndrew Steffl, Adam Shinn (Southwest Research Institute – Boulder)With thanks to Fran Bagenal, Peter Delamere, Nick Schneider and the UVIS teamMOP 2011, Boston

  2. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations • Introduction • The Io Plasma Torus in 2 Minutes • The Role of Hot electrons • Longitudinal Variations

  3. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations 1. Io’s Volcanoes

  4. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations 2. Atmospheric Losses

  5. Introduction IPT in 2 minutes IPT in 2 minutes Hot Electrons Longitudinal Variations 3. Torus emitting in the FUV

  6. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations Mass & Energy Flow Through the Torus Bagenal & Delamere (2010)

  7. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations UVIS EUV Spectrum of the Dusk Ansa

  8. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations Sinusoidal Variations of the Torus Dusk Ansa

  9. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations Phase of Azimuthal Variations with Time Slope yields a 10.07-hour period; System III period is 9.925 hours

  10. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations Lomb-Scargle Periodogram Periodogram peak at 10.07 hours

  11. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations Note about System IV System IV is not causedby thelocal plasma rotation speed Thomas et al. (2001) Brown (1995)

  12. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations Sinusoidal Variations of the Torus Dusk Ansa

  13. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations 29 Days = 1/fSystem III - 1/f“System IV”

  14. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations  Dual Hot Electron Model • Two variations of hot electrons • One drifting relative to System III • One fixed in System III • IV = 50% • III = 40% • III = 290º

  15. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations Mechanism for producing a System III-fixed variation in hot electrons Conclusions Hess et al., 2011 (submitted) Frank & Patterson 2000

  16. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations Conclusions • Most of the neutral material picked up into the Io plasma torus comes from the extended neutral clouds • Hot electrons are required to supply the Io plasma torus with energy • Cassini UVIS observed significant longitudinal variations in the Io torus composition • The variations drift at the System IV period • The amplitude varies on the beat period of System IV and System III • Models with 2 longitudinal variations of hot electrons can qualitatively match the torus behavior • Hess et al. 2011 propose a mechanism for producing hot electrons with a peak at 290º System III • What produces the System IV component?

  17. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations System III System IV System IV System IV – System III System IV + System III System III System IV System IV + System III System IV – System III

  18. Introduction IPT in 2 minutes Hot Electrons Longitudinal Variations

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