Aurora Borealis

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<ol><li> 1. AURORA BOREALIS Kilian Schnberger December 2009 SAS 8 Norwegian Area Studies </li><li> 2. Content 1. Name and Origins 2. History 3. Northern Light Times 4. Morphing the Magnetic Field 5. Forming of Auroras 6. The Aurora Oval 7. Aurora Forms 8. Dancing Colours 9. Sources </li><li> 3. Name and Origins Name: Aurora Borealis Latin for Northern Dawn One of the most impressive natural phenomena First recorded incident: La Caverne de Lascaux SW France Fascinates and terrifies humans Aurora Legends: Every northern culture has oral legends about the aurora, passed down for generations </li><li> 4. Medieval Age People believed that the polar light is a bad omen Fearing the red light Especially while it is very rare in Middle Europe The aurora was for example described as heaven battles or as candles Image source: gedds.pfrr.alaska.edu Image source: gedds.pfrr.alaska.edu </li><li> 5. Fridtjof Nansen This Norwegian polar explorer tried to reach the north pole with his ship Fram in 1895-96 He was blocked by ice but made many woodcuts and drawings about the aurora Fridtjof Nansen 1861-1930 Image source: gedds.pfrr.alaska.edu Image source: gedds.pfrr.alaska.edu </li><li> 6. Northern Light Times Solar phenomenon in the Ionosphere Occurs while periods of high solar activity 80-200km above ground connected to the magnetosphere http://ds9.ssl.berkeley.edu/lws_gems/6/images_6/ion470.jpg Image source: http://ds9.ssl.berkeley.edu/ Image source: gedds.pfrr.alaska.edu </li><li> 7. Solar Winds Solar winds are caused by energy released by the sun Extension of Suns corona High speed plasma Image Source: http://talklikeaphysicist.com/wp- content/uploads/2008/10/sun-corona- mass- </li><li> 8. A long way towards earth Interactions with the Ionosphere solar wind (speed 450km/h) carries a weak magnetic field Interaction between this and the magnetic field of earth Changes form of the earths magnetosphere energy dissipates into gaseous form, causing Auroras or stays in electric form Dangers: Interrupting satellite transmissions / power grids </li><li> 9. Morphing the magnetic field earth has a magnetosphere surrounding the planet solar wind flowing past the earth solar wind and the magnetosphere are two electrically conducting fluids with magnetic fields plasma and atoms collide energy flow causes a change in magnetic field Image Source: http://odin.gi.alaska.edu/FAQ/ </li><li> 10. Magnetosphere Earth has a dipole magnetic field similar to a bar magnet Invisible magnetic field lines entering at the north pole, exiting at the south pole periods of high solar activity interaction between the solar wind and magnetosphere solar winds effect the comet shape Bare Magnet Image source: gedds.pfrr.alaska.edu Image source: wikipedia.com </li><li> 11. Forming of Auroras Repeat: solar wind collides with atoms of the upper atmosphere Altitudes of 80-200km Frequency usually follows the 11-year sunspot maximum cycle. Peak 3 years after the peak of the sunspot cycle. Image source: nasa.com </li><li> 12. The Aurora Oval Image Source: Akasofu, Syun-Ichi. Secrets of the Aurora Borealis The aurora is often visible at high latitudes Magnetic field pressure is strongest Most often: Oval located between 65 and 75 degrees latitude Oval ranges from 500 to 1500 km in width Zone statistically defined </li><li> 13. A aurora seen from space Nasa Image source: http://en.wikipedia.org/wiki/File:Aurora_Borealis.jpg </li><li> 14. Where the aurora can be seen Number of nights per year aurora can be seen at certain locations Northern Norway: 100 nights each per year Rest of Norway: 10 nights every year Middle Europe: 1 to 0,1 nights each years http://gedds.pfrr.alaska.edu/aurora/Images/w1.jpg Image source: http://gedds.pfrr.alaska.edu/ </li><li> 15. Simple aurora structure elements Images by Tom McEwan Image source: http://gedds.pfrr.alaska.edu/ </li><li> 16. Complex formations Images by Tom McEwan Complex formations out of the shown elements: Curl Curtain Omega band Corona Pulsating aurora Combinations are also possible Image source: fotocommunity.de </li><li> 17. Why colourfull? High-speed discharge electrons collide with atoms and molecules in the upper atmosphere Different kinds of atoms and molecules produce different colours of lights Emissions between 100 and 300 km altitude Image source: fotocommunity.de </li><li> 18. Dancing Colours &gt;500km: Hydrogen and Helium atoms take over 200-500km: Oxygen atoms green / brownish-red brightest single line emission of the aurora 100-200km: Nitrogen molecules blue / red blue/purple border green line emission (oxygen) is quenched at this altitude The color of light emitted depends on the wavelength of a photon: visible light ~400-700 nanometers (blue-red) Akasofu, Syun-Ichi. Secrets of the Aurora Borealis. </li><li> 19. Auroras on other planets Planets with magnetic fields have Auroras Jupiter, Saturn have highest concentrations Caused by Solar Winds NASA image of Jupiter aurora in UV, Hubble Space Telescope: Image source: http://en.wikipedia.org/wiki/File:Jupiter.Aurora.HST.UV.jpg </li><li> 20. Sources Bryson, G. (2003): Nordlicht a study of the aurora borealis, Mathematics Senior Thesis Presentation Blixt, E. (2006): Optical flow analysis of the aurora borealis, Trans. Geoscience and Remote sensing Canadian Space Agency, Aurora Borealis Northern Lights University of Alaska, http:// asahi-classroom.gi.alaska.edu/ (18.11.2009) http://wikipedia.org (18.11.2009) http://www.fotocommunity.de (18.11.2009) Profil Thilo Bubek http://nasa.com (18.11.2009) </li></ol>

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