Spectropolarimetery of umbral fine structures from Hinode: evidence for magnetoconvection

We present spectropolarimetric analysis of umbral dots and a light bridge fragment that show dark lanes in G-band images. Umbral dots show upflow as well as associated positive Stokes V area asymmetry in their central parts. Larger umbral dots show downflow patches in their surrounding parts that are associated with negative Stokes V area asymmetry. Umbral dots show weaker magnetic field in central part and higher magnetic field in peripheral area. Umbral fine structures are much better visible in total circularly polarized light than in continuum intensity. Umbral dots show a temperature deficit above dark lanes. The magnetic field inclination shows a cusp structure above umbral dots and a light bridge fragment. We compare our observational findings with 3D magnetohydrodynamic simulations.

[1]  S. Solanki,et al.  Stratification of Sunspot Umbral Dots from Inversion of Stokes Profiles Recorded by Hinode , 2008, 0805.4324.

[2]  Toshifumi Shimizu,et al.  Polarization Calibration of the Solar Optical Telescope onboard Hinode , 2008 .

[3]  T. Rimmele.  On the Relation between Umbral Dots, Dark-cored Filaments, and Light Bridges , 2007 .

[4]  R. Rezaei,et al.  Hinode observations reveal boundary layers of magnetic elements in the solar photosphere , 2007, 0711.0408.

[5]  N. Weiss,et al.  Magnetic flux separation in photospheric convection , 2002 .

[6]  T. Berger,et al.  Formation Process of a Light Bridge Revealed with the Hinode Solar Optical Telescope , 2007, 0709.2527.

[7]  N. Weiss,et al.  FINE STRUCTURE IN SUNSPOTS , 2004 .

[8]  L. B. Rubio,et al.  Heat transfer in sunspot penumbrae. Origin of dark-cored penumbral filaments , 2008, 0806.0804.

[9]  G. Scharmer,et al.  Fine structure, magnetic field and heating of sunspot penumbrae , 2005, astro-ph/0508504.

[10]  L. B. Rubio,et al.  Detection of sea-serpent field lines in sunspot penumbrae , 2007, 0712.2983.

[11]  V. Pillet,et al.  The Thermal and Magnetic Structure of Umbral Dots from the Inversion of High-Resolution Full Stokes Observations , 2004 .

[12]  R. Jain,et al.  Evidence for Magnetoconvection in Sunspot Umbral Dots , 2007 .

[13]  T. Kosugi,et al.  The Hinode (Solar-B) Mission: An Overview , 2007 .

[14]  L. Bharti,et al.  Observations of Dark Lanes in Umbral Fine Structure from the Hinode Solar Optical Telescope: Evidence for Magnetoconvection , 2007 .

[15]  L. Bharti,et al.  Enhanced Joule Heating in Umbral Dots , 2007, 0705.1141.

[16]  J. Almeida,et al.  Observation and interpretation of the asymmetric Stokes Q, U, and V line profiles in sunspots , 1992 .

[17]  A. Choudhuri.  The dynamics of magnetically trapped fluids. I - Implications for umbral dots and penumbral grains , 1986 .

[18]  Sami K. Solanki,et al.  Sunspots: An overview , 2003 .

[19]  A. Hanslmeier,et al.  Photometry of umbral dots , 2005 .

[20]  T. Rimmele,et al.  Detection of opposite polarities in a sunspot light bridge: evidence of low-altitude magnetic reconnection , 2007, astro-ph/0701674.

[21]  J. C. del Toro Iniesta,et al.  TO APPEAR IN APJ LETTERS Preprint typeset using LATEX style emulateapj v. 10/09/06 VECTOR SPECTROPOLARIMETRY OF DARK-CORED PENUMBRAL FILAMENTS WITH HINODE , 2022 .

[22]  J. C. del Toro Iniesta,et al.  Inversion of Stokes profiles , 1992 .

[23]  N. Weiss.  Umbral and penumbral magnetoconvection , 2002 .

[24]  J. Borrero.  The structure of sunspot penumbrae IV. MHS equilibrium for penumbral flux tubes and the origin of , 2007, 0704.3219.

[25]  S. Solanki,et al.  Evidence of magnetic field wrapping around penumbral filaments , 2007, 0712.2548.

[26]  M. Schuessler,et al.  Magnetoconvection in a Sunspot Umbra , 2006, astro-ph/0603078.

[27]  E. Parker.  Sunspots and the physics of magnetic flux tubes. IX. Umbral dots and longitudinal overstability , 1979 .