Polar Faculae Magnetism - High Altitude Observatory · PDF filePolar Faculae Magnetism ......

Polar Faculae Magnetism

Adur Pastor Yabar[1,2] ([email protected])

María Jesús Martínez González[1,2] Manuel Collados Vera[1,2]

[1] Instituto de Astrofísica de Canarias

[2] Universidad de La Laguna

Polarimetry: From the Sun to Stars and Stellar Environments; IAU Symposium 305; 3rd December

Outline

•  What we know from Magnetograms •  What we know from Spectropolarimetric

Analysis •  Where We Are •  Conclusions

Adur Pastor Yabar; IAU Symposium 305; 3rd December

WHAT WE KNOW FROM MAGNETOGRAMS


Bibliography

•  Babcock & Babcock 1955 •  Sheeley 1964 •  Severny et al. 1971 •  Svalgaard et al. 1978 •  Okunev & Kneer 2004 •  Blanco Rodríguez et al. 2007


Magnetograms: Polar Scenario

Polar magnetism characterized by: – Not null net flux over the polar cap – Opposite signs at both poles

Babcock & Babcock 1955



Polar magnetism characterized by: – Not null net flux over the polar cap – Opposite signs at both poles – Polarity inversion shifted a quarter of the cycle

compared to activity belt

http://solarscience.msfc.nasa.gov/dynamo.shtml


Polar magnetism characterized by: – Not null net flux over the polar cap – Opposite signs at both poles – Polarity inversion shifted a quarter of the cycle

compared to activity belt – Magnetic flux concentrated in small structures

(Facula) – Polar Facula with both LOS signs

(70/80%-30/20%)

Blanco Rodríguez et al. 2007



What kind of local magnetic field configuration gives:

-polar cap region with net sign -mix (80%/20%) LOS magnetogram?

Tests: We consider several magnetic field

configurations in the normal to the Sun's surface reference system and construct the LOS magnetogram


Magnetograms: Polar Scenario σ nin/nout

Negative flux [%] latitude [75º-90º]

Isotropic - 50.03

Half-Isotropic - 43.51

10 0/1 9.1

30 0/1 29.34

10 1/2 28.82

10 1/3 35.25

10 1/5 22.24

30 1/5 35.99

From magnetograms one can not determine the net flux through the surface of the polar cap

WHAT WE KNOW FROM SPECTROPOLARIMETRIC ANALYSIS


Bibliography

•  Tsuneta et al. 2008 •  Blanco Rodríguez et al. 2010 •  Ito et al. 2010 •  Shiota et al. 2012


Ambiguity problem

Ambiguity problem

Ito et al. 2010 Shiota et al. 2012

Ambiguity problem


Ito et al. 2010

Ambiguity problem


Ito et al. 2010

Vertical Undetermined Horizontal 0º-40º ; 140º-180º 40º-70º ; 110º-140º 70º-110º

Ambiguity problem


Ito et al. 2010

Solut. 1 Vertical Vertical Horizontal Vertical Undetermined Horizontal

Solut 2. Vertical Undetermined Undetermined Horizontal Undetermined Horizontal

Final Solution

Most Vertical

Vertical Horizontal Undetermined Undetermined ¿Undetermined?

Problems with this method

•  A particular configuration is imposed •  Undetermined magnetic fields are not studied •  It is more or less accurate statistically but not

in a one to one comparison


WHERE WE ARE


Where We Are

•  2014-04-14 Data from SST (La Palma, Spain) in 6173Å FeI


Where We Are

•  2014-04-14 Data From SST (La Palma, Spain) in 6173Å FeI

Stokes I

South Pole

Where We Are


Stokes Q

South Pole

Where We Are


Stokes U

South Pole

Where We Are


Stokes V

South Pole

Where We Are


•  We have performed Inversions using SIR (Ruíz Cobo and del Toro Iniesta 1992)


Where We Are


•  Inversions have been done

Magnetic Field Intensity

South Pole

Where We Are



Magnetic Field Inclination

South Pole

Where We Are



Magnetic Field Azimuth

South Pole

Where We Are


•  Inversions have been done •  Ambiguity solution: First attempts – We impose an equally probable azimuth in local

reference frame


Where We Are


•  Inversions have been done •  Ambiguity solution: First attempts – We Impose An Equally Probable Azimuth in Local

Reference Frame

CONCLUSION


Conclusions •  A unipolar local magnetic configuration can easily

give a mix LOS magnetogram at high latitudes (above 60º)

•  Transformation from LOS magnetic configuration to Local is not direct!! –  If radial configuration is assumed this step

becomes direct but also not accurate –  If LOS magnetograms are dominated by one sign,

a magnetic polarity is dominant in the polar cap but it is not possible to know how much

•  There is not yet a correct azimuth disambiguation method for polar magnetic fields

THANKS!

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