What are Auroras? Where can you see them? What makes them happen?

1. AURORAS ALIGHT!Presented by:Dr. Nahide Craig and Dr. Vassilis AngelopoulosContributions by:The scientists and engineers behind the THEMIS teamURL: http://ds9.ssl.berkeley.edu/themis

2. OUTLINE • What are Auroras? • Where can you see them? • What makes them happen? • Does our Sun have anything to do with it? • How does a space mission study Auroras?

3. What are Auroras? What colors do you see? How far up in the sky do you think these colors are?

4. Beautiful Dancing Lights in the Sky…

5. … have fascinated people from pre-historic times… Cro-Magnon cave-paintings: “macaronis” may be earliest depiction of aurora (30,000 B.C.)

6. … and have given rise to mythological creatures, have driven folklore, and have influenced the course of history, religion and art. “Fu-Pao, the mother of the Yellow Empire Shuan-Yuan, saw strong lightning moving around the star Su,which belongs to the constellation of Bei-Dou, and the light illuminated thewhole area. After that she became pregnant.”, Oldest written auroral citing, 2600 B.C., China.

7. The Sun • The Sun is the closest star, close-enough to feel its heat. • The stars are other Suns but very far away. • The Sun is a giant ball of very hot gas that shines under its own power. • The Sun is 109 times the diameter of Earth. • Over 1,000,000 Earths could fit inside the Sun • The Sun’s light is not smooth but has spots. This is the second clue we have thatour Sun is, in fact, quite temperamental!

8. It all starts at the SUN Today we know that the auroral lights are the first clue we have that: our planet isunder attack!! not by space aliens but by our very our own star: The Sun.

9. The SUN we feel and cannot feel …but seen up-close, by our extended senses, our instrument sensors, the Sun is wildly active, explosive! We can sense the quiet, steady Sun which gives us beautiful sunsets…

10. Satellites, like the ones on the left, carry our sensors in space, above the Earth’s atmosphere to: • Image the Sun free from the blurring of atmosphere’s haze, and • Measure the gas in the environment between the Sun and Earth

11. Loopy Flares! What do the shapes you see in the movie remind you of?

12. Magnetic loops – They are everywhere!! Bar magnet guides iron filings (iron dust) in loops between North (N) and South (S) poles (Two poles = a dipole). Opposite poles attract, like poles repel. Many dipoles make a mess!! Sun’s magnetism also guides its outer layers (solar particles) in loops. Sun’s dipoles move because Sun’s surface is in motion. Many dipoles together flare up!

13. Magnetism exists both at Sun and Earth (dynamo)

14. Earth’s “Magnetic Tail” – Magnetotail, Shaped by the Solar Wind Our Sun throws off dense clouds of super-hot gas that sail across the solar system and slam into Earth at a million miles per hour! The Earth’s magnetic field looks something like a comet with Earth at the head of the comet and a long (million-mile) magneto-tail flowing out behind Earth.

15. Aurora: Why does it happen at night? When the solar wind passes Earth, it drags the magnetic tail far out into space and compresses it. Stretched magnetic lines break and then (re) connect into a different shape. When this happens, magnetic field lines snap towards Earth like stretched rubber-bands. Gases guided by the magnetic field speed up towards Earth and hit the upper atmosphere at the North and South poles of Earth.

16. Aurora: Where does the light come from? In a split second, each atom gives off a tiny burst of light in colors of red, blue, green or yellow. When the light is added together, it forms beautiful curtains of shimmering light in the sky that we see as Aurora.

17. WHAT Do We Not Know? Where in the Magnetotail does the magnetosphere snap and then pop with Aurora? (snap-crackle-pop? or crackle-pop-snap?) crackle snap pop

18. Our atmosphere has both oxygen and nitrogen: Oxygen glows in green-yellow and the deep red Nitrogen glows in blue and the purplish-red. Why Different Colors??

19. : Ground Based Observatory How does THEMIS answer this question? Ground based observatories completely cover North American sector; determine auroral breakup within 1-3s … … while THEMIS’s space-based probes determine the time and location of the activity in space within <10s.

20. Mission Characteristics • THEMIS is scheduled to be launched with a Delta II rocket in the fall of 2006. • THEMIS has five probes (one is in-orbit spare) andhas a 2 year lifetime. • THEMIS’ five identical probes measure particles and fields in orbits which align in the magnetotail every 4 days over North America.

21. THEMIS Five-Probe Deployment

22. Boom Deployments

23. How is it built? Testing Chamber

24. Scientist John Bonnell: How is the Boom tested?

25. Removal of the Axial Electric Field Boom

26. Magnetometer Booms Tested for Deployment

27. Wire Booms Delivered for Integration to Probes

28. Probe Structure Probe Carrier Structure

29. Informal Education Programs.E/PO Web Site: http://ds9.ssl.berkeley.edu/themis • Aurorae Gallery • Activities • News & Events • In The Classroom • Mission Science • About Us