ASYMMETRY IN TEMPERATURE OF SOLAR POLES SOLAR PHYSICS January 18th, 2013 Pilar Herrero Sinovas 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  Jupiter would accelerate Ulysses out of the ecliptic plane to high latitudes.  The ESA-NASA Ulysses robotic probe was launched in October  Jupiter would accelerate Ulysses out of the ecliptic plane to high latitudes.

Ulysses:Overflying the Poles Three times overflew the solar poles:  Solar minimum  Solar maximum  Solar minimum Three times overflew the solar poles:  Solar minimum  Solar maximum  Solar minimum

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

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!  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!

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

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

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

What are the causes?  All data from first flight over the poles (minimum)

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

Asymmetry in Area Different Areas! North Larger Different Areas! North Larger

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

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: km/s  Lower expansion factor: 5% 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: km/s  Lower expansion factor: 5%

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