Abstract
The photospheric magnetic field in the Sun’s polar region is not well observed compared to the low-latitude regions. Data are periodically missing due to the Sun’s tilt angle, and the noise level is high due to the projection effect on the line-of-sight (LOS) measurement. However, the large-scale characteristics of the polar magnetic field data are known to be important for global modeling. This report describes a new method for interpolating the photospheric field in polar regions that has been tested on MDI synoptic maps (1996 – 2009). This technique, based on a two-dimensional spatial/temporal interpolation and a simple version of the flux transport model, uses a multi-year series of well-observed, smoothed north (south) pole observations from each September (March) to interpolate for missing pixels at any time of interest. It is refined by using a spatial smoothing scheme to seamlessly incorporate this filled-in data into the original observation starting from lower latitudes. For recent observations, an extrapolated polar field correction is required. Scaling the average flux density from the prior observations of slightly lower latitudes is found to be a good proxy of the future polar field. This new method has several advantages over some existing methods. It is demonstrated to improve the results of global models such as the Wang–Sheeley–Arge (WSA) model and MHD simulation, especially during the sunspot minimum phase.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Arge, C.N., Pizzo, V.J.: 2000, Improvement in the prediction of solar wind conditions using near-real time solar magnetic field updates. J. Geophys. Res. 105, 10465.
Arge, C.N., Luhmann, J.G., Odstrčil, D., Schrijver, C.J., Li, Y.: 2004, Stream structure and coronal sources of the solar wind during the May 12th, 1997 CME. J. Atmos. Solar-Terr. Phys. 66, 1295.
Berger, T.E., Lites, B.W.: 2003, Weak-field magnetogram calibration using Advanced Stokes Polarimeter flux density maps – II. SOHO/MDI full-disk mode calibration. Solar Phys. 213, 213.
Hayashi, K.: 2005, Magnetohydrodynamic simulations of the solar corona and solar wind using a boundary treatment to limit solar wind mass flux. Astrophys. J. Suppl. 161, 480.
Hayashi, K., Zhao, X., Liu, Y.: 2008, MHD simulations of the global solar corona around the Halloween event in 2003 using the synchronic frame format of the solar photospheric magnetic field. J. Geophys. Res. 113, 7104.
Hoeksema, J.T.: 1984, Structure and evolution of the large scale solar and heliospheric magnetic fields. Ph.D. thesis, Stanford University.
King, J.H., Papitashvili, N.E.: 2005, Solar wind spatial scales in and comparisons of hourly wind and ACE plasma and magnetic field data. J. Geophys. Res. 110, 2104.
Linker, J.A., Mikić, Z., Biesecker, D.A., Forsyth, R.J., Gibson, S.E., Lazarus, A.J., Lecinski, A., Riley, P., Szabo, A., Thompson, B.J.: 1999, Magnetohydrodynamic modeling of the solar corona during Whole Sun Month. J. Geophys. Res. 104, 9809.
Liu, Y., Zhao, X., Hoeksema, J.T.: 2004, Correction of offset in MDI/SOHO magnetograms. Solar Phys. 219, 39.
Liu, Y., Hoeksema, J.T., Zhao, X., Larson, R.M.: 2007, MDI synoptic charts of magnetic field: Interpolation of polar fields. Bull. Am. Astron. Soc. 38, 129.
Luhmann, J.G., Lee, C.O., Li, Y., Arge, C.N., Galvin, A.B., Simunac, K., Russell, C.T., Howard, R.A., Petrie, G.: 2009, Solar wind sources in the late declining phase of cycle 23: Effects of the weak solar polar field on high speed streams. Solar Phys. 256, 285.
Meunier, N.: 2005, Magnetic network dynamics: Activity level, feature size and anchoring depth. Astron. Astrophys. 436, 1075.
Neugebauer, M., Forsyth, R.J., Galvin, A.B., Harvey, K.L., Hoeksema, J.T., Lazarus, A.J., Lepping, R.P., Linker, J.A., Mikić, Z., Steinberg, J.T., von Steiger, R., Wang, Y.M., Wimmer-Schweingruber, R.F.: 1998, Spatial structure of the solar wind and comparisons with solar data and models. J. Geophys. Res. 103, 14587.
Owens, M.J., Spence, H.E., McGregor, S., Huges, W.J., Quinn, J.M., Arge, C.N., Riley, P., Linker, J., Odstricil, D.: 2008, Metrics for solar wind prediction models: comparison of empirical, hybrid and physics-based schemes with 8 years of L1 observations. Space Weather 6, S08001.
Riley, P., Linker, J., Mikić, Z., Lionello, R.: 2001, MHD modeling of the solar corona and inner heliosphere: Comparison with observations. In: Song, P., Singer, H.J., Siscoe, G.L. (eds.) Space Weather, AGU Geophys. Monogr. 125, 159.
Schatten, K.H., Wilcox, J.M., Ness, N.F.: 1969, A model of interplanetary and coronal magnetic fields. Solar Phys. 6, 442.
Scherrer, P.H., Bogart, R.S., Bush, R.I., Hoeksema, J.T., Kosovichev, A.G., Schou, J., Rosenberg, W., Springer, L., Tarbell, T.D., Title, A., Wolfson, C.J., Zayer, I., Team, M.E.: 1995, The Solar oscillations investigation – Michelson Doppler Imager. Solar Phys. 162, 129.
Schrijver, C.J., DeRosa, M.L.: 2003, Photospheric and heliospheric magnetic fields. Solar Phys. 212, 165.
Svalgaard, L., Duvall, T.L. Jr., Scherrer, P.H.: 1978, The strength of the Sun’s polar fields. Solar Phys. 58, 225.
Tran, T., Bertello, L., Ulrich, R.K., Evans, S.: 2005, Magnetic fields from SOHO MDI converted to the Mount Wilson 150 foot solar tower scale. Astrophys. J. Suppl. 156, 295.
Wang, Y.M., Sheeley, N.R. Jr.: 1988, The solar origin of long-term variations of the interplanetary magnetic field strength. J. Geophys. Res. 93, 11227.
Wang, Y.M., Sheeley, N.R. Jr.: 1990, Solar wind speed and coronal flux-tube expansion. Astrophys. J. 355, 726.
Wang, Y.M., Sheeley, N.R. Jr.: 1992, On potential field models of the solar corona. Astrophys. J. 392, 310.
Zhao, X., Hoeksema, J.T., Scherrer, P.H.: 1999, Changes of the boot-shaped coronal hole boundary during Whole Sun Month near sunspot minimum. J. Geophys. Res. 104, 9735.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Sun, X., Liu, Y., Hoeksema, J.T. et al. A New Method for Polar Field Interpolation. Sol Phys 270, 9–22 (2011). https://doi.org/10.1007/s11207-011-9751-4
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11207-011-9751-4