1. MAGNETIC FIELD USES SOUND WAVES TO IGNITE SUN'S RING OF FIRE Stuart Jefferies, University of Hawaii, HI Viggo Hansteen, University of Oslo, Norway Scott McIntosh, Southwest Research Institute, Boulder, CO Bart De Pontieu, Lockheed Martin Solar & Astrophysics Lab, Palo Alto, CA “Scientists discover what molds the Sun’s Ring of Fire”

2. What is the Sun’s Ring of Fire? Solar Chromosphere: 20,000 F Sandwiched between surface (10,000 F) and corona (2 million F) Produces UV radiation that may influence Earth’s climate

3. Why is the Chromosphere Hot ? Movie taken with NASA’s STEREO A spacecraft in EUV light. Note the jets at the limb and the flickering on the disk.

4. Why is the Chromosphere Hot & Barbed ? Movie taken with NASA/ESA’s SOHO spacecraft in EUV light. Zoomed in 3x on the South polar limb.

5. Movie taken with Solar Optical Telescope (NASA/JAXA) onboard Japanese Hinode satellite The Chromosphere is dominated by thin (100-500 mile wide) jets shooting up and down with velocities of order 10-50 miles/s traversing 3,000 miles in a few minutes. Why is the Chromosphere Hot, Barbed & Dynamic?

6. What Forges the Sun’s “Ring of Fire”? Magnetic field concentrations that are inclined from the vertical provide “portals” for the trapped waves to leak out and travel upwards. Illustration by Zina Deretsky, National Science Foundation

7. Waves leak out of interior of the Sun… The dynamic magnetic field (jostled by convection) forms temporary “cracks” (twinkling) for the low frequency waves to pass through. Movie from MOTH (Magneto-Optical filters at Two Heights - NSF, Office of Polar Programs)

8. …Leaking sound waves form strong Shock Waves…. Chromospheric Movie from Swedish Solar Telescope (Spain) Courtesy Luc Rouppe van der Voort, Michiel van Noort Continuously driving fountains of plasma upwards at supersonic speeds.

9. Computer Simulations Temperature Velocity Courtesy of Institute of Theoretical Astrophysics, University of Oslo, Norway Dynamic interplay of magnetic field and waves form jets that are very similar to those observed

10. Funding Credits The research presented was supported by the National Aeronautics and Space Adminstration (NNG05GM75G, NNG06GG79G, NNG06GC89G), the National Science Foundation (ANT-0338251, ATM-0541567) and by the Research Council of Norway through grant 146467/420 and grants of computing time from the Programme for Supercomputing.

11. Relevant Publications Hansteen, V.H., De Pontieu, B., Rouppe van der Voort, L.H.M., van Noort, M., Carlsson, M. 2006: “Dynamic Fibrils Are Driven by Magnetoacoustic Shocks”, Astrophysical Journal, 647, L73. McIntosh, S.W., Jefferies, S.M., 2006: “Modification of the Acoustic Cut-Off Frequency by Magnetic Field Inclination”, Astrophysical Journal Letters, 647, L77. Jefferies, S.M., McIntosh, S.W., Armstrong, J.D., Cacciani, A., Bogdan, T.J., Fleck, B., 2006: “Magnetoacoustic Portals and the Basal Heating of the Solar Chromosphere”, Astrophysical Journal, 648, L151. De Pontieu, B., Hansteen, V.H., Rouppe van der Voort, L.H.M., van Noort, M., Carlsson, M., 2006: “High-Resolution Observations and Modeling of Dynamic Fibrils” Astrophysical Journal, 655, 624. Rouppe van der Voort, L.H.M., B. De Pontieu, B., Hansteen, V. H., Carlsson, M., van Noort, M., 2007: “Magnetoacoustic Shocks as a Driver of Quiet-Sun Mottles”, Astrophysical Journal, 660, L169.