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  • Ancient Eskimo stories often are associated with notions of life after death. Some thought that the aurora was a narrow and dangerous pathway for the departed souls to heaven.

Transcript

  • 1. AURORA BOREALIS Kilian Schönberger December 2009 SAS 8 – Norwegian Area Studies
  • 2. Content
    • Name and Origins
    • History
    • Northern Light Times
    • Morphing the Magnetic Field
    • Forming of Auroras
    • The Aurora Oval
    • Aurora Forms
    • Dancing Colours
    • Sources
  • 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
  • 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
  • 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
  • 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
  • 7. Solar Winds
    • Solar winds are caused by energy released by the sun
    • Extension of Sun’s corona
    • High speed plasma
    Image Source: http://talklikeaphysicist.com/wp-content/uploads/2008/10/sun-corona-mass-
  • 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 earth‘s magnetosphere
    • energy dissipates into gaseous form, causing Aurora’s or stays in electric form
    • Dangers: Interrupting satellite transmissions / power grids
  • 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/
  • 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
  • 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
  • 12. The Aurora Oval
    • 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
    Image Source: Akasofu, Syun-Ichi. Secrets of the Aurora Borealis
  • 13. A aurora seen from space Nasa Image source: http://en.wikipedia.org/wiki/File:Aurora_Borealis.jpg
  • 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/
  • 15. Simple aurora structure elements Images by Tom McEwan Image source: http://gedds.pfrr.alaska.edu/
  • 16. Complex formations
    • Complex formations out of the shown elements:
    • Curl
    • Curtain
    • Omega band
    • Corona
    • Pulsating aurora
    • Combinations are also possible
    Images by Tom McEwan Image source: fotocommunity.de
  • 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
  • 18. Dancing Colours
    • >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.
  • 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
  • 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)