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