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ASYMMETRY IN TEMPERATURE OF SOLAR POLES

ASYMMETRY IN TEMPERATURE OF SOLAR POLES. SOLAR PHYSICS January 18th, 2013 Pilar Herrero Sinovas. Introduction: How was the asymmmetry discovered?. Ulysses:Trajectory. The ESA-NASA Ulysses robotic probe was launched in October 1990.

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ASYMMETRY IN TEMPERATURE OF SOLAR POLES

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  1. ASYMMETRY IN TEMPERATURE OF SOLAR POLES SOLAR PHYSICS January 18th, 2013 Pilar Herrero Sinovas

  2. Introduction: How was the asymmmetry discovered?

  3. Ulysses:Trajectory • The ESA-NASA Ulysses robotic probe was launched in October 1990. • Jupiter would accelerate Ulysses out of the ecliptic plane to high latitudes.

  4. Ulysses:Overflying the Poles Three times overflew the solar poles: • 1994-1995 Solar minimum • 2000-2001 Solar maximum • 2007-2008 Solar minimum

  5. Ulysses: SWICS The Solar Wind Ion Composition Spectrometer (SWICS): - Temperatures - Mean speeds of solar-wind ions

  6. Ulysses: SWICS • First orbit: SWICS measured the ratio O7+/O6+ • Lower in the North Pole Continuity equation: n, u: densidad y velocidad R: Tasa de recombinación C: Tasa de ionización Lower T in North Pole!

  7. SWICS: Results • Average temperature of the Sun's polar wind is about one million degrees C. • But over North Pole the wind is about 44.000 degrees cooler than over South!

  8. Magnetic Field • The "cool spot" follows the north magnetic pole when the sun's poles flip.

  9. What are the causes? UNKNOWN! • But related asymmetries have been studied for Polar Coronal Holes (PCH): - Area - Magnetic Flux Density - Wind Speed - Expansion Factor

  10. What are the causes? • All data from first flight over the poles (minimum)

  11. Asymmetry in Area • 1996 large polar coronal holes extend to or below 50º • North larger than the South: N = 8% S = 7%

  12. Asymmetry in Area Different Areas! North Larger

  13. Asymmetry in magnetic flux densities North: Magnetic Flux Density Twice lower!

  14. Expansion Factor and Velocity Expansion factor: Compares the magnitude of the photospheric magnetic field at the footpoint of the tube with its magnitude at 2.5 solar radii. North: • Higher velocity: 15-20 km/s • Lower expansion factor: 5%

  15. Summary But no definitive answer exists!! North Pole: Lower: - Temperature - Magnetic Flux - Expansion Factor Higher: - Area - Velocity

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