AuroraBy: Sara Fukuhara & Kalei Kahookele

What is Aurora?• Natural light display in

the sky• Mostly in the polar

region• Observed at night• Typically occurs in

ionosphere

What causes Aurora?

• Energetic charged particles from magnetosphere• Immediate cause: precipitating energetic particles

(electrons/protons that are energized in geospace)• This process draws its energy from the interaction of

Earth’s magnetosphere with the solar wind• Energy is transferred from solar winds to

magnetosphere– Magnetosphere responds to reconnection by dumping

electrons/protons into the high latitude upper atmosphere where energy of plasma can be dissipated resulting in aurora

What causes the color?

• Composition & density of the atmosphere & the altitude of the aurora determine possible light emissions

• Excited atom/molecule returns to ground state & sends a photon with a specific energy

• Energy of the photon Color• Energetic electrons can split molecules of air into

nitrogen & oxygen atoms• Photons of aurora have signature colors of

nitrogen/oxygen

Color Example:

• Oxygen atoms strongly emit photons in two colors: – green and red, red is brownish that is at the limit of what the

human eye can see

• Red auroral emission is very bright, we can barely see it

Photographic Film

• See more red aurora on photos than with unaided eye

• More atomic oxygen at high altitudes red aurora tends to be on top of the regular green aurora

• Colors are a mixture of all the auroral emissions• Overall impression is a greenish-whitish glow• Very intense aurora gets a purple edge at bottom

(purple: mixture of blue and red emissions from nitrogen molecules)

Altitude• Bottom edge 100 km altitude• Altitude where the mission comes from depends

on the energy of the energetic electrons that make the aurora

• More energy the deeper the electron gets into the atmosphere

• High altitude aurora: 600 km (350 miles)about where space shuttle flies

Shape• Magnetic field confines motion of auroral electrons• The charged particles can only move freely when

parallel to magnetic field (in the direction of or against)• Near earth: motions of electrons are guided by Earth’s

magnetic field• An electron spirals along into the atmosphere, it stays

on/near this field line even when it makes a collision curtain shape

About Aurora Borealis

• Named after Roman goddess of dawn• Thought to be produced by sunlight

reflected from snow/ice or refracted light

• Become brighter, more distinctive, & spread over larger area two days after solar activity

• Often occur near equinoxes

About Aurora Borealis

• Cause: radiation emitted as light from atoms in upper atmosphere as they’re hit by fast moving electrons & protons

• Energy particles from sun collide with Earth’s magnetic field

• Kind of atom determines color

Anywhere else?• Aurora can be found on other

planets• Venus: has no magnetic

field irregular shaped aurora• Saturn, Earth, Jupiter: has an

intrinsic magnetic dipole field oval shaped crowns of light on both hemispheres

Video

• http://www.youtube.com/watch?v=YJBrMXSn-hU

Works Cited

• "Aurora FAQ." Aeronomy and Auroral Physics at the GI. Web. 07 Mar. 2011. <http://odin.gi.alaska.edu/FAQ/>.

• "Northern Lights - Aurora Borealis." Fairbanks Alaska Visitor Information Site. Web. 07 Mar. 2011. <http://fairbanks-alaska.com/northern-lights-alaska.htm>.

• "The Northern Lights - Where, When and What." Tromsø Geophysical Observatory. Web. 07 Mar. 2011. <http://geo.phys.uit.no/articl/nord_eng.html>.

• Stern, David P. "Secrets of the Polar Aurora." Educational Web Sites. Web. 07 Mar. 2011. <http://www.phy6.org/Education/aurora.htm>.