Sound Waves
From the Northern
Lights
Photo courtesy of Bjorn Jorgensen, 18 January 2005, near Tromsø, Norway
http://www.spaceweather.com/aurora/images2005/17jan05/Jorgensen1.jpg
Jada Maxwell
“Synergy means behavior of whole systems unpredicted
by the behavior of their parts taken separately.”
- Buckminster Fuller
What creates the aurora?
Sound waves from the aurora
Wave transformation on the Sun
Beginning to answer my question
Can magnetic waves in the aurorae transform into sound
waves?
What creates the aurora?
Chain of EventsThe 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
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
South-North Magnetic Orientation
of CME
North-South Magnetic Orientation
of CME
Magnetic Reconnection on Dayside of Earth
Magnetic Field Lines are Drawn Back to Magnetotail
Magnetotail is Compressed
Magnetic Reconnection in Magnetotail
Particles Spiral Down Field Lines
Image: Fundamentals of Physics, 2005
Particles 2
Collide with atomic and molecular oxygen and nitrogen
Emit energy as light
Particles Spiral Down Field Lines
This Creates the
Aurorae
Image courtesy of Shawn Malonehttp://www.lakesuperiorphoto.com
Northern Lights = Aurora Borealis
Southern Lights = Aurora Australis
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
Psychological
Freezing Breath
“Brush discharge”
Explanations of Audible Sounds
Humans can hear between 20 and 20,000 Hertz (Hz)
Infrasound is below 20 Hz
Currently being investigated
Gas expansion
Evidence of Infrasound from Aurorae
The Sun Creates Sound Waves
Sound Waves on the Sun Created by Convection
Sound Waves Propagate through Sun’s Atmosphere
Sun
Energy of Sound Waves is Transformed into Magnetic
Waves
Sun
Alfvén waves (s-mode)
Magnetosonic waves (p-mode)
Types of Magnetic Waves
Images courtesy of Georgia State Universityhttp://hyperphysics.phy-astr.gsu.edu/hbase/sound/tralon.html
BBC animations
Can magnetic waves in the aurorae
transform into sound waves?
My Question
Magnetic Waves
Earth
Transform into Sound Waves
Earth
Finding Beta
Beta = β =
Gas (atmospheric) PressureMagnetic 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 = 1β = 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