Sound Waves From the Northern Lights

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

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What creates the aurora?
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Chain of Events
The aurora is created by a chain of events,
beginning with energy from the sun.
Image courtesy of Tom Michalikhttp//faculty.rmwc
.edu/tmichalik/solarwind.htm
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The Magnetosphere
Image courtesy of Minnesota Technologhttp//techn
olog.it.umn.edu/technolog/novdec97/cover.htm
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Coronal Mass Ejection (CME)
Illustration by Steele Hill, courtesy of
NASAhttp//sohowww.nascom.nasa.gov/localinfo/stee
le.html
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South-North Magnetic Orientation of CME
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North-South Magnetic Orientation of CME
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Magnetic Reconnection on Dayside of Earth
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Magnetic Field Lines are Drawn Back to Magnetotail
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Magnetotail is Compressed
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Magnetic Reconnection in Magnetotail
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Particles Spiral Down Field Lines
Image Fundamentals of Physics, 2005
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Particles 2
Particles Spiral Down Field Lines

• Collide with atomic and molecular oxygen and
  nitrogen

• Emit energy as light

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This Creates the Aurorae

• Northern Lights Aurora Borealis
• Southern Lights Aurora Australis

Image courtesy of Shawn Malonehttp//www.lakesupe
riorphoto.com
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Nearly Mirror Images
Aurora Borealis
Aurora Australis
Images courtesy of NOAAhttp//sec.noaa.gov/pmap/
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Can we hear the aurorae?

• Anecdotal evidence of auroral sounds

• hissing, popping, crackling, swooshing
• corresponds with motions of light

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6 minutes

• Sound would take at least 6 minutes to travel
  from the aurora to the ground

• No recordings of audible aurorae

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Explanations of Audible Sounds

• Psychological
• Freezing Breath
• Brush discharge

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Evidence of Infrasound from Aurorae

• Humans can hear between 20 and 20,000 Hertz (Hz)
• Infrasound is below 20 Hz
• Currently being investigated
• Gas expansion

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The Sun Creates Sound Waves
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Sound Waves on the Sun Created by Convection
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Sound Waves Propagate through Suns Atmosphere
Sun
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Energy of Sound Waves is Transformed into
Magnetic Waves
Sun
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Types of Magnetic Waves

• Alfvén waves (s-mode)

• Magnetosonic waves (p-mode)

Images courtesy of Georgia State
Universityhttp//hyperphysics.phy-astr.gsu.edu/hb
ase/sound/tralon.html
BBC animations
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My Question
Can magnetic waves in the aurorae transform into
sound waves?
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Magnetic Waves
Earth
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Transform into Sound Waves
Earth
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Finding Beta
Gas (atmospheric) Pressure
Beta ß
Magnetic Field Pressure
ß 1 ?
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Resonance

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

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Resonance in the Aurora
When ß 1,

• Energy from magnetic waves can be transferred to
  the atmosphere
• Found the right frequency

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When Beta 1
ß 1 ?

• At 120 km
• Near bottom of aurorae

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More Questions to Investigate

• How does ß 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?

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Thanks to

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

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Image Sources

• NOAA (National Oceanic Atmospheric
  Administration)http//sec.noaa.gov/pmap/
• NASAhttp//sohowww.nascom.nasa.gov/localinfo/ste
  ele.html
• SpaceWeather.com http//www.spaceweather.com/auro
  ra/images2005.htm
• Shawn Malonehttp//www.lakesuperiorphoto.com
• Tom Michalikhttp//faculty.rmwc.edu/tmichalik/so
  larwind.htm
• Minnesota Technologhttp//technolog.it.umn.edu/t
  echnolog/novdec97/cover.htm
• Fundamentals of Physics, Halliday/Resnick/Walker,
  John Wiley Sons, 2005, p 746