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The Post-Cassini View of the Io Plasma Torus Andrew Steffl, Adam Shinn (Southwest Research Institute – Boulder) With thanks to Fran Bagenal, Peter Delamere,

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Presentation on theme: "The Post-Cassini View of the Io Plasma Torus Andrew Steffl, Adam Shinn (Southwest Research Institute – Boulder) With thanks to Fran Bagenal, Peter Delamere,"— Presentation transcript:

1 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

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

3 IntroductionIPT in 2 minutesHot ElectronsLongitudinal Variations 1. Io’s Volcanoes

4 IntroductionIPT in 2 minutesHot ElectronsLongitudinal Variations 2. Atmospheric Losses

5 IPT in 2 minutesIntroductionIPT in 2 minutesHot ElectronsLongitudinal Variations 3. Torus emitting in the FUV

6 Bagenal & Delamere (2010) Mass & Energy Flow Through the Torus IntroductionIPT in 2 minutesHot ElectronsLongitudinal Variations

7 UVIS EUV Spectrum of the Dusk Ansa IntroductionIPT in 2 minutesHot ElectronsLongitudinal Variations

8 Sinusoidal Variations of the Torus Dusk Ansa IntroductionIPT in 2 minutesHot ElectronsLongitudinal Variations

9 Phase of Azimuthal Variations with Time Slope yields a 10.07-hour period; System III period is 9.925 hours IntroductionIPT in 2 minutesHot ElectronsLongitudinal Variations

10 Lomb-Scargle Periodogram Periodogram peak at 10.07 hours IntroductionIPT in 2 minutesHot ElectronsLongitudinal Variations

11 Note about System IV Brown (1995)Thomas et al. (2001) System IV is not caused by the local plasma rotation speed IntroductionIPT in 2 minutesHot ElectronsLongitudinal Variations

12 Sinusoidal Variations of the Torus Dusk Ansa IntroductionIPT in 2 minutesHot ElectronsLongitudinal Variations

13 29 Days = 1/f System III - 1/f “System IV” IntroductionIPT in 2 minutesHot ElectronsLongitudinal Variations

14 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  IntroductionIPT in 2 minutesHot ElectronsLongitudinal Variations

15 Conclusions Frank & Patterson 2000 IPT in 2 minutesHot ElectronsLongitudinal VariationsIntroduction Hess et al., 2011 (submitted) Mechanism for producing a System III-fixed variation in hot electrons

16 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? IntroductionIPT in 2 minutesHot ElectronsLongitudinal Variations

17 IntroductionIPT in 2 minutesHot ElectronsLongitudinal Variations System III System IV – System III System IV System III System IV – System III System IV + System III

18 IntroductionIPT in 2 minutesHot ElectronsLongitudinal Variations


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