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
“Synergy means behavior of whole systems unpredicted by the behavior of their parts taken separately.”- Buckminster Fuller
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
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
The Magnetosphere Image courtesy of Minnesota Technologhttp://technolog.it.umn.edu/technolog/novdec97/cover.htm
Coronal Mass Ejection (CME) Illustration by Steele Hill, courtesy of NASAhttp://sohowww.nascom.nasa.gov/localinfo/steele.html
Particles Spiral Down Field Lines Image: Fundamentals of Physics, 2005
Particles 2 Particles Spiral Down Field Lines • Collide with atomic and molecular oxygen and nitrogen • Emit energy as light
This Creates the Aurorae • Northern Lights = Aurora Borealis • Southern Lights = Aurora Australis Image courtesy of Shawn Malonehttp://www.lakesuperiorphoto.com
Nearly Mirror Images Aurora Borealis Aurora Australis Images courtesy of NOAAhttp://sec.noaa.gov/pmap/
Can we hear the aurorae? • Anecdotal evidence of auroral sounds • hissing, popping, crackling, swooshing • corresponds with motions of light
6 minutes • Sound would take at least 6 minutes to travel from the aurora to the ground • No recordings of audible aurorae
Explanations of Audible Sounds • Psychological • Freezing Breath • “Brush discharge”
Evidence of Infrasoundfrom Aurorae • Humans can hear between 20 and 20,000 Hertz (Hz) • Infrasound is below 20 Hz • Currently being investigated • Gas expansion
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
My Question Can magnetic waves in the aurorae transform into sound waves?
Magnetic Waves Earth
Finding Beta Gas (atmospheric) Pressure Beta = β = Magnetic Field Pressure β = 1 ?
Resonance • All material has a frequency that it vibrates at • Matching the frequency allows the material to absorb energy • Singing wine glass
Resonance in the Aurora When β = 1, • Energy from magnetic waves can be transferred to the atmosphere • Found the right frequency
When Beta = 1 β= 1 ? • At 120 km • Near bottom of aurorae
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?
Thanks to: • Dr. E.J. Zita for her guidance and helpful discussions • Beth Stinson for instruction in PowerPoint
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