Dawn-Dusk Oscillation of the Io Plasma Torus and the Vasyliunas E-V Theorem

1. Dawn-Dusk Oscillation of the Io Plasma Torus and the Vasyliunas E-V Theorem A. J. Dessler Dept. of Atmospheric Science Texas A&M University College Station, Texas and B. R. Sandel Lunar and Planetary Laboratory University of Arizona Tucson, Arizona Boston MOP Meeting 15 July 2011

2. IO TORUS DAWN-DUSK OFFSET Torus w/ Ribbon on inner (i.e., Jupiter) side Approaching Ansa Dawn Ansa Dusk Ansa Receding Ansa Viewed from Voyager Viewed from Earth

3. OSCILLATION OF IO TORUS Approaching Dawn A Dusk Ansa A is Magnetic Anomaly at λIII ~110° Receding Ansa Voyager Earth Approaching Dawn A Dusk Ansa Receding Ansa

4. Magnetic Anomaly – Announced (John Clarke et al. 2002 Birmingham DPS meeting). Quantitatively defined (Denis Grodent et al. 2008 JGR and Hess et al. 2011 JGR). Weak B

5. Dessler & Sandel, 1979 data from Voyager Schneider & Trauger, 1991 data from Earth 12 years apart

6. Anomaly magnetic field maps to equator Areas A and B are equal

7. Flux tube Big-Foot resistant to interchange No Anomaly change in B-field at Equator

8. EFFECT OF MAGNETIC ANOMALY Limited Outflow A Dawn Magnetic-Anomaly fluxtubes map to equator to form impoundment region Limited Outflow A Dusk

10. Dawn minus Dusk Distance Central Meridian Longitude (System III) CML provides snapshots of Ribbon Distances

11. Outflow from torus toward tail causes Torus Offset Dawn minus Dusk Ribbon Distance Anomaly between Dawn and Noon Maximumoutflow – Max Offset Anomaly between Dusk and Midnight Minimum outflow – Minimum Offset

12. Maximum Outflow from torus toward Tail Max Offset Dawn Dusk Noon

13. Local-Time range of Anomaly at given CML viewed from Earth Noon to Dawn Anomaly out of the way. Maximum Outflow – Max Offset Dawn minus Dusk Ribbon Distance Anomaly ~110°

14. Minimum Outflow from torus toward Tail Midnight Dawn Dusk Noon

15. Local-Time positions of Anomaly at given CML viewed from Earth Noon to Dawn Anomaly out of the way. Maximum Outflow Dawn minus Dusk Ribbon Distance Midnight to Dusk Anomaly Impedes Outflow

16. The Improved Magnetic-Anomaly Model explains the torus oscillation. • Other Jovian spin-periodic phenomena can be explained by this Magnetic-Anomaly Model. • The Vasyliunas E-V Theorem is important. E is a result of V, • E cannot cause V. • Please contact me for more information, wild ideas, or discussion. • e-mail: Alex.Dessler@gmail.com Concluding Thoughts

17. Extra slides follow

18. TIME-VARYING ELECTRIC-FIELD HYPOTHESIS This idea suffers two flaws: (a) Where is the E-field created so it knows Jupiter’s rotational phase? Problem: As plasma flows down tail, a varying V X B field is created at different distances — all longitude phases are mapped back to torus. Therefore, E-field will not work. (b) Inconsistent with the Vasyliunas E-V Theorem.GRL 2001. Problem:V X B can create E, but E cannot cause magnetospheric plasma to move. No E-field will work.

20. 1. The Magnetic Anomaly vital to the Magnetic-Anomaly Model has been discovered, and the Vasyliunas E-V Theorem provided needed guidance. 2. The torus oscillation is explained by an improved Magnetic-Anomaly Model. The Magnetic-Anomaly Model is open for exploitation. Examples of Jovian spin-periodic phenomena that could be explained by the Magnetic-Anomaly Model: a. How Active Sector works. It contains many Jovian spin-periodic phenomena. See Sect. 10.7 in "PJM". b. The 10-hour Plasmoid "bubbles" travelling down the Jovian tail reported by McComas et al. Science 2007. c. The Simpson Clock – highest energy and flux of relativistic electrons released from Jupiter when Magnetic Anomaly faces sunward. d. The Lyman-alpha bulge. e. Extension to Saturn spin-periodic phenomena? CONCLUSIONS

23. Longitudinal Extent of Anomaly A A

25. Position of Anomaly for given CML Observed from Earth A Midnite A Dusk A Dawn A Midnite A Noon A Dawn A Dusk A Noon