ASYMMETRY IN TEMPERATURE OF SOLAR

POLES

ASYMMETRY IN TEMPERATURE OF SOLAR

POLES

SOLAR PHYSICSJanuary 18th, 2013

Pilar Herrero Sinovas

SOLAR PHYSICSJanuary 18th, 2013

Pilar Herrero Sinovas

Introduction: How was the asymmmetry discovered?Introduction: How was the asymmmetry discovered?

Ulysses:TrajectoryUlysses:Trajectory The ESA-NASA Ulysses

robotic probe was launched in October 1990.

Jupiter would accelerate Ulysses out of the ecliptic plane to high latitudes.

The ESA-NASA Ulysses robotic probe was launched in October 1990.

Jupiter would accelerate Ulysses out of the ecliptic plane to high latitudes.

Ulysses:Overflying the PolesUlysses:Overflying the Poles

Three times overflew the solar poles:

1994-1995 Solar minimum 2000-2001 Solar maximum 2007-2008 Solar minimum

Three times overflew the solar poles:

1994-1995 Solar minimum 2000-2001 Solar maximum 2007-2008 Solar minimum

Ulysses: SWICSUlysses: 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: SWICSUlysses: SWICS First orbit: SWICS measured the ratio O7+/O6+ Lower in the North Pole

Continuity equation:

n, u: densidad y velocidad

R: Tasa de recombinaciónC: 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 recombinaciónC: Tasa de ionización

Lower T in North Pole!

SWICS: ResultsSWICS: 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!

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!

Magnetic FieldMagnetic Field The "cool spot" follows the north

magnetic pole when the sun's poles flip.

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

What are the causes?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?What are the causes?

All data from first flight over the poles (minimum)

All data from first flight over the poles (minimum)

Asymmetry in AreaAsymmetry 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 AreaAsymmetry in Area

Different Areas!North Larger

Different Areas!North Larger

Asymmetry in magnetic flux densities

Asymmetry in magnetic flux densities

North:Magnetic Flux DensityTwice lower!

North:Magnetic Flux DensityTwice lower!

Expansion Factor and Velocity

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%

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%

SummarySummaryNorth Pole:Lower: - Temperature- Magnetic Flux- Expansion FactorHigher:- Area- Velocity

North Pole:Lower: - Temperature- Magnetic Flux- Expansion FactorHigher:- Area- Velocity

But no definitive answer exists!!

But no definitive answer exists!!