Post on 31-Dec-2015
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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!!