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Sound Waves From the Northern Lights

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  1. Sound Waves From the Northern Lights Jada Maxwell Photo courtesy of Bjorn Jorgensen, 18 January 2005, near Tromsø, Norway http://www.spaceweather.com/aurora/images2005/17jan05/Jorgensen1.jpg

  2. “Synergy means behavior of whole systems unpredicted by the behavior of their parts taken separately.”- Buckminster Fuller

  3. Can magnetic waves in the aurorae transform into sound waves? • What creates the aurora? • Sound waves from the aurora • Wave transformation on the Sun • Beginning to answer my question

  4. What creates the aurora?

  5. The aurora is created by a chain of events, beginning with energy from the sun. Chain of Events Image courtesy of Tom Michalikhttp://faculty.rmwc.edu/tmichalik/solarwind.htm

  6. The Magnetosphere Image courtesy of Minnesota Technologhttp://technolog.it.umn.edu/technolog/novdec97/cover.htm

  7. Coronal Mass Ejection (CME) Illustration by Steele Hill, courtesy of NASAhttp://sohowww.nascom.nasa.gov/localinfo/steele.html

  8. South-North Magnetic Orientation of CME

  9. North-South Magnetic Orientation of CME

  10. Magnetic Reconnection on Dayside of Earth

  11. Magnetic Field Lines are Drawn Back to Magnetotail

  12. Magnetotail is Compressed

  13. Magnetic Reconnection in Magnetotail

  14. Particles Spiral Down Field Lines Image: Fundamentals of Physics, 2005

  15. Particles 2 Particles Spiral Down Field Lines • Collide with atomic and molecular oxygen and nitrogen • Emit energy as light

  16. This Creates the Aurorae • Northern Lights = Aurora Borealis • Southern Lights = Aurora Australis Image courtesy of Shawn Malonehttp://www.lakesuperiorphoto.com

  17. Nearly Mirror Images Aurora Borealis Aurora Australis Images courtesy of NOAAhttp://sec.noaa.gov/pmap/

  18. Can we hear the aurorae? • Anecdotal evidence of auroral sounds • hissing, popping, crackling, swooshing • corresponds with motions of light

  19. 6 minutes • Sound would take at least 6 minutes to travel from the aurora to the ground • No recordings of audible aurorae

  20. Explanations of Audible Sounds • Psychological • Freezing Breath • “Brush discharge”

  21. Evidence of Infrasoundfrom Aurorae • Humans can hear between 20 and 20,000 Hertz (Hz) • Infrasound is below 20 Hz • Currently being investigated • Gas expansion

  22. The Sun Creates Sound Waves

  23. Sound Waves on the Sun Created by Convection

  24. Sound Waves Propagate through Sun’s Atmosphere Sun

  25. Energy of Sound Waves is Transformed into Magnetic Waves Sun

  26. Types of Magnetic Waves • Alfvén waves (s-mode) • Magnetosonic waves (p-mode) Images courtesy of Georgia State Universityhttp://hyperphysics.phy-astr.gsu.edu/hbase/sound/tralon.html BBC animations

  27. My Question Can magnetic waves in the aurorae transform into sound waves?

  28. Magnetic Waves Earth

  29. Transform into Sound Waves Earth

  30. Finding Beta Gas (atmospheric) Pressure Beta = β = Magnetic Field Pressure β = 1 ?

  31. Resonance • All material has a frequency that it vibrates at • Matching the frequency allows the material to absorb energy • Singing wine glass

  32. Resonance in the Aurora When β = 1, • Energy from magnetic waves can be transferred to the atmosphere • Found the right frequency

  33. When Beta = 1 β= 1 ? • At 120 km • Near bottom of aurorae

  34. More Questions to Investigate • How does β vary? • Compare gas expansion theory to wave transformation • How much might Alfvén and magnetosonic waves each contribute to this effect? • Which is more likely to transform?

  35. Thanks to: • Dr. E.J. Zita for her guidance and helpful discussions • Beth Stinson for instruction in PowerPoint

  36. Image Sources: • NOAA (National Oceanic & Atmospheric Administration)http://sec.noaa.gov/pmap/ • NASAhttp://sohowww.nascom.nasa.gov/localinfo/steele.html • SpaceWeather.com http://www.spaceweather.com/aurora/images2005.htm • Shawn Malonehttp://www.lakesuperiorphoto.com • Tom Michalikhttp://faculty.rmwc.edu/tmichalik/solarwind.htm • Minnesota Technologhttp://technolog.it.umn.edu/technolog/novdec97/cover.htm • Fundamentals of Physics, Halliday/Resnick/Walker, John Wiley & Sons, 2005, p 746