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Interpolated polar field for CR1914: 7 Methods

Description of Method 5. Comparison. Method. Polar field interpolation methods. 1 2 3 4 5 6 7. Observational polar field data. After Surace fitting. Ø. Using observed polar field data. 1D cubic spline interpolation method; Potential field method;

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Interpolated polar field for CR1914: 7 Methods

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  1. Description of Method 5 Comparison Method Polar field interpolation methods 1 2 3 4 5 6 7 Observational polar field data After Surace fitting Ø Using observed polar field data. • 1D cubic spline interpolation method; • Potential field method; • Modified 1D cubic spline interpolation method (smoothed); • Polar field model method (B=Bp*cos(colatitude)^8) (e.g. Svalgaard et al 1978); • 2D temporal interpolation method; • 2D spatial interpolation method; • flux transportation model based method (data from Schrijver and DeRosa, 2002). Method 1 2D fitting Method 5 Polar field measurement in southern pole from 1996 to 2004. Method 6 CR2021 CR2024 CR2027 Comparison Comparison Method Method Detail here 1 2 3 4 5 6 7 1 2 3 4 5 6 7 Polar field reversal CR1914 CR1917 CR1920 CR1967 CR1971 CR1974 Heliospheric field CR1960 (02/2000-03/2000) CR1975 (04/2001-05/2001) CR1972 CR1983 Synoptic Maps of Magnetic Field from MDI Magnetograms: Polar Field Interpolation.Y. Liu, J. T. Hoeksema, X. P. Zhao, R. M. Larson – Stanford University Question: How best to infer the polar field? Interpolated polar field for CR1914: 7 Methods • This poster compares seven methods for interpolation of the polar magnetic field for the MDI synoptic charts. By examining the coronal and heliospheric magnetic field computed from the synoptic charts based on a Potential Field Source Surface model (PFSS), and by comparing the heliospheric current sheets and footpoints of open fields with the observations, we conclude that the coronal and heliospheric fields calculated from the synoptic charts are sensitive to the polar field interpolation, and a time-dependent interpolation method (Method 5) using the observed polar fields is the best among the seven methods investigated. • Discussion & Conclusion • Method 1: This method is bad because closed fields are computed in polar regions in solar minimum; • Method 2: This method is based on Method 1 (bad); • Method 3: Improved but questionable during polar field reversal. When trailing field reaches high latitude but the polar field is not reversed, the interpolated polar field might already give a reversed polar field because this method uses low latitude data to interpolate polar field (see CR1967); • Method 4: generally is good, but might be questionable in solar maximum because no evidence has been presented to show this model is still a good approximation in solar maximum; • Method 5 might be the best; • Method 6 also uses the low latitude data to fill in the polar regions. It may be questionable during polar field reversal (see CR1967); • Method 7: strongly depends on flux transportation model that would be very complicated. Also show earlier polar field reversal (CR1967).

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