Auroras - Borealis (north) & Australis (south)

1. Aurora Borealis Made by Riquette Mory 01

2. A u r o r a s Auroras are called also northern and southern (polar) lights or Aurora. Auroras are observed at night in the polar regions. Auroras are called after the Greek goddess of dawn Aurora. Auroras are most visible closer to the poles due to the longer periods of darkness and the magnetic field. The aurora australis (Latin word for “of the south”) the southern polar lights are the counterpart of the northern lights. They are visible only from high southern latitudes in Antarctica andSouth America. 02 November 24, 2009 2 Aurora Borealis Riquette Mory

3. A u r o r a s Auroras are the result of the emissions of photons in the Earth's upperatmosphere: oxygenemissions Green or brownish-red, depending on the amount of energy absorbed. Nitrogenemissions Blue or red. Blue if the atom regains an electron after it has been ionized. Red if returning to ground state from an excited state. November 24, 2009 3 Aurora Borealis Riquette Mory

4. A u r o r a s Northern Lights Southern Lights A predominantly red aurora australis 03 Aurora Borealis Aurora australis 1994 from Bluff, New Zealand Aurora australis (September 11, 2005) as captured by NASA's IMAGE satellite November 24, 2009 4 Aurora Borealis Riquette Mory

5. A u r o r a s Auroras are formed When a "solar wind" of charged particles from the Sun enters Earth's magnetic field, accelerating electrically charged particles trapped within. The high-speed particles then crash into Earth's upper atmosphere over the Polar Regions, causing the atmosphere to emit a ghostly, multicolored glow. 04 November 24, 2009 5 Aurora Borealis Riquette Mory

6. November 24, 2009 6 Aurora Borealis Riquette Mory A u r o r a s Forms and magnetism Typically the aurora appears either as a diffuse glow or as "curtains" that approximately extend in the east-west direction. Some times, they form "quiet arcs"; or sometimes ("active aurora"), “Each curtain consists of many parallel rays, each lined up with the local direction of the magnetic field lines, suggesting that aurora is shaped by Earth's magnetic field. Indeed, satellites show electrons to be guided by magnetic field lines, spiraling around them while moving towards Earth.” Northern lights over Calgary

7. November 24, 2009 7 Aurora Borealis Riquette Mory A u r o r a s On other planets “Jupiter aurora. The bright spot at far left is the end of field line to Io; spots at bottom lead to Ganymede and Europa.” “Both Jupiter and Saturn have magnetic fields much stronger than Earth's (Jupiter's equatorial field strength is 4.3 gauss, compared to 0.3 gauss for Earth), and both have large radiation belts.” Aurora has been observed on Jupiter and Saturn, Uranus and Neptune, most clearly with the Hubble Space Telescope.

8. On Oct. 30th, the interplanetary magnetic field (IMF) near Earth tilted south, an orientation that weakens our planet's magnetic defenses against solar wind. Solar wind poured into Earth's magnetosphere and sparked an early Halloween display of Northern Lights over Alaska. November 24, 2009 Aurora Borealis Riquette Mory 8 A u r o r a s Niels Giroud, Nordland, Norway Oct. 24, 2009 Wioleta Zarzycka, IcelandOct. 25, 2009 Michael H Davies, Canada Oct. 27, 2009

9. A u r o r a s The deepest solar minimum in nearly 100 years has not put a stop to Northern Lights around the Arctic Circle. The geomagnetic field has been quite active this month (Nov. 09), Producingdisplays of particular beauty over Scandinavia. November 24, 2009 9 Aurora Borealis Riquette Mory Tom Roland, NorwayNov. 10, 2009 John, Fairbanks, AlaskaNov. 8, 2009 Babak Tafreshi, NorwayNov. 7, 2009

10. Frequency of Occurrence November 24, 2009 10 Aurora Borealis Riquette Mory Geomagnetic storms that ignite auroras actually happen more often during the months around the equinoxes. It is known that during spring and autumn, the interplanetary magnetic field and that of Earth link up. I hope that you enjoyed the Aurora Borealis Beauty