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Azimuth ambiguity resolution from dBz/dz

Azimuth ambiguity resolution from dBz/dz. M. Kubo (ISAS/JAXA), K. Shimada (University of Tokyo), K. Ichimoto, S. Tsuneta (NAOJ) and SOT-team. Azimuth ambiguity. Resolution of azimuth ambiguity is very important for - determination of magnetic field structure.

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Azimuth ambiguity resolution from dBz/dz

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  1. Azimuth ambiguity resolution from dBz/dz M. Kubo (ISAS/JAXA), K. Shimada (University of Tokyo), K. Ichimoto, S. Tsuneta (NAOJ) and SOT-team

  2. Azimuth ambiguity • Resolution of azimuth ambiguity is very important for • - determination of magnetic field structure. • - calculation of shear angle, current density, and helicity. • We try to resolve the azimuth ambiguity from only B = 0 with • no assumption (L. Wu & G. Ai, 1990, ACTA). • Magnetic fields must satisfy B = 0 . dBz/dz < 0 dBz/dz > 0 If we can know sign of dBz/dz, the azimuth angle is determined. We calculate the sign of dBz/dz by using (1) two different photospheric line profiles (Fe I 6301.5Å and Fe I 6302.5Å) (2) line-core and wing of one photospheric line profile (Fe I 6301. 5Å) Bx, By Bx, By

  3. dBz/dz from two different line profiles • We obtain two Bz values using Fe I 6301.5Å and Fe I 6302.5Å lines. • - SOT/SP obtains full stokes profiles of Fe I 6301.5Å and Fe I 6302.5Å. • Milne-Eddington inversion code is applied for each line • to derive the magnetic field strengths with different height. • Formation height of Fe I 6301.5Å is slightly higher than that of Fe I 6302.5Å. • Bz (6301.5Å) - Bz (6302.5Å) >0 •  dBz/dz > 0 • Bz (6301.5Å) - Bz (6302.5Å) <0 •  dBz/dz < 0 Stokes V profile

  4. Test Case • We use Holweger & Muller model atmosphere to make synthesized Stoke profiles. • Field strength has height gradient (dB/d =  300), • and inclination does not vary with height. • We examine 36 cases for dBz/dz >0 and 36 cases for dBz/dz <0. inclination: 0 = vertical to the solar surface, 90 = horizontal to the solar surface

  5. Result1 • A percentage of correct answers for both  dBz/dz is 39 % (14/36). • When filling factor becomes a free parameter, the percentage increases to 67% . • The percentage of correct answers are not improved when thermodynamic • parameters are fixed to values derived from both lines or when weight of • Stokes-V increases in the ME inversion. input parameters: ◇:  = 10 [deg] △:  = 45 [deg] ×:  = 80 [deg] red: dBz/dz > 0 blue: dBz/dz < 0 dBz/dz > 0 dBz/dz < 0 (Filling factor are fixed to 1 in this case.)

  6. Result1 • A percentage of correct answers for both  dBz/dz is 39 % (14/36). • When filling factor becomes a free parameter, the percentage increases to 67% . • The percentage of correct answers are not improved when thermodynamic • parameters are fixed to values derived from both lines or when weight of • Stokes-V increases in the ME inversion. input parameters: ◇:  = 10 [deg] △:  = 45 [deg] ×:  = 80 [deg] red: dBz/dz > 0 blue: dBz/dz < 0 dBz/dz > 0 dBz/dz < 0 (Filling factor are fixed to 1 in this case.)

  7. Difference of response function between line-core and wing • We investigate difference between two Bz • values derived from Stokes profiles • around line core and wing. • The line core profile represents magnetic fields • in the upper atmosphere in comparison with • magnetic fields derived from the wing. • Bz (line core) - Bz (wing) > 0  dBz/dz > 0 • Bz (line core) - Bz (wing) < 0  dBz/dz < 0 • The line core is defined as line center  70 mÅ. • The wing is defined as -300mÅ to -70 mÅ. • We use Fe I 6301.5Å, because a response • function of Stokes V to Bz for Fe I 6301.5Å • is sharper than that of Fe I 6302.5Å. Response function of Stokes-V to Bz Line center: 6301.5Å Stokes V profile (6301.5Å)

  8. Result2 • A percentage of correct answers for both  dBz/dz is 86 % (31/36), and • it increase to 97% (29/30) for field strength > 500 Gauss. • We may have to change wavelength sampling for line-core and wing • with a width of Zeeman splitting. input parameters: ◇:  = 10 [deg] △:  = 45 [deg] ×:  = 80 [deg] red: dBz/dz > 0 blue: dBz/dz < 0 dBz/dz > 0 dBz/dz < 0 (Filling factor and Doppler shift are fixed to 1 and 0 respectively in this case.)

  9. Summary and Future Works • Difference between the response functions of Stokes V for line-core • and wing would be useful for calculating the sign of dBz/dz. • - We have to test this method for • (1) many cases with various parameters (Doppler, filling factor..) • (2) profiles including noise • (3) observed Stokes profile • We like to find the best way to calculate the sign of dBz/dz. • - We will try to derive the sign of dBz/dz by using • (1) Neural network • (2) PCA • (3) Inversion with height gradient • (4) etc

  10. Stokes V profiles fitted for line core and wing A B C input line core wing

  11. Response function of Stokes-V to Bz, FeI6302.5A

  12. Response function of Stokes-V to Bz, FeI6301.5A

  13. l = -168 ~ +168mA

  14. 6301.5A 6302.5A

  15. FeI6302.5A Bt=100G Residual of ME fit

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