Abstract
At the surface of the Sun, acoustic waves appear to be affected by the presence of strong magnetic fields in active regions. We explore the possibility that the inclined magnetic field in sunspot penumbrae may convert primarily vertically-propagating acoustic waves into elliptical motion. We use helioseismic holography to measure the modulus and phase of the correlation between incoming acoustic waves and the local surface motion within two sunspots. These correlations are modeled by assuming the surface motion to be elliptical, and we explore the properties of the elliptical motion on the magnetic-field inclination. We also demonstrate that the phase shift of the outward-propagating waves is opposite to the phase shift of the inward-propagating waves in stronger, more vertical fields, but similar to the inward phase shifts in weaker, more-inclined fields.
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Basu, S., Antia, H.M., Bogart, R.S.: 2004, Ring-diagram analysis of the structure of solar active regions. Astrophys. J. 610, 1157.
Braun, D.C.: 1995, Scattering of p-modes by sunspots. I. Observations. Astrophys. J. 451, 859.
Braun, D.C.: 1997, Time – distance sunspot seismology with GONG data. Astrophys. J. 487, 447.
Braun, D.C., Lindsey, C.: 2000, Phase-sensitive holography of Solar activity. Solar Phys. 192, 307.
Cally, P.S.: 2005, Local magnetohelioseismology of active regions. Mon. Not. Roy. Astron. Soc. 358, 353.
Cally, P.S.: 2007, What to look for in the seismology of solar active regions. Astron. Nachr. 328, 286.
Cally, P.S., Goossens, M.: 2007, Three-dimensional MHD wave propagation and conversion to Alfvén waves near the Solar surface. I. Direct numerical solution. Solar Phys. doi:10.1007/s11207-007-9086-3.
Cally, P.S., Crouch, A.D., Braun, D.C.: 2003, Probing sunspot magnetic fields with p-mode absorption and phase shift data. Mon. Not. Roy. Astron. Soc. 346, 381.
Couvidat, S., Rajaguru, S.P.: 2007, Contamination by surface effects of time – distance helioseismic inversions for sound speed beneath sunspots. Astrophys. J. 661, 558.
Couvidat, S., Birch, A.C., Kosovichev, A.G.: 2006, Three-dimensional inversion of sound speed below a sunspot in the Born approximation. Astrophys. J. 640, 516.
Crouch, A., Cally, P.S.: 2003, Mode conversion of solar p modes in non-vertical magnetic fields. I. Two-dimensional model. Solar Phys. 214, 201.
Duvall, T.L., Jr., Jefferies, S.M., Harvey, J.W., Pomerantz, M.A.: 1993, Time – distance helioseismology. Nature 362, 430.
Hanasoge, S.M., Couvidat, S., Rajaguru, S.P., Birch, A.C.: 2007, Impact of locally suppressed wave sources on helioseismic travel times. 707.
Korzennik, S.G.: 2006, The cookie cutter test for time-distance tomography of active regions. In: Fletcher, K., Thompson, M. (eds.) Proceedings of SOHO 18/GONG 2006/HELAS I, Beyond the Spherical Sun 624, ESA, Noordwijk, 60.
Kosovichev, A.G., Duvall, T.L.J., Scherrer, P.H.: 2000, Time – distance inversion methods and results. Solar Phys. 192, 159.
Lindsey, C., Braun, D.C.: 2000, Basic principles of Solar acoustic holography. Solar Phys. 192, 261.
Lindsey, C., Braun, D.C.: 2005a, The acoustic showerglass. I. Seismic diagnostics of photospheric magnetic fields. Astrophys. J. 620, 1107.
Lindsey, C., Braun, D.C.: 2005b, The acoustic showerglass. II. Imaging active region subphotospheres. Astrophys. J. 620, 1118.
Mickey, D.L., Canfield, R.C., Labonte, B.J., Leka, K.D., Waterson, M.F., Weber, H.M.: 1996, The imaging vector magnetograph at Haleakala. Solar Phys. 168, 229.
Rajaguru, S.P., Birch, A.C., Duvall, T.L., Jr., Thompson, M.J., Zhao, J.: 2006, Sensitivity of time – distance helioseismic measurements to spatial variation of oscillation amplitudes. I. Observations and a numerical model. Astrophys. J. 646, 543.
Rajaguru, S.P., Sankarasubramanian, K., Wachter, R., Scherrer, P.H.: 2007, Radiative transfer effects on Doppler measurements as sources of surface effects in sunspot seismology. Astrophys. J. 654, L175.
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., MDI Engineering Team, 1995, The Solar oscillations investigation – Michelson Doppler imager. Solar Phys. 162, 129.
Schunker, H., Cally, P.S.: 2006, Magnetic field inclination and atmospheric oscillations above solar active regions. Mon. Not. Roy. Astron. Soc. 372, 551.
Schunker, H., Braun, D.C., Cally, P.S.: 2007, Surface magnetic field effects in local helioseismology. Astron. Nachr. 328, 292.
Schunker, H., Braun, D.C., Cally, P.S., Lindsey, C.: 2005, The local helioseismology of inclined magnetic fields and the showerglass effect. Astrophys. J. 621, L149.
Weiss, N.O., Thomas, J.H., Brummell, N.H., Tobias, S.M.: 2004, The origin of penumbral structure in sunspots: Downward pumping of magnetic flux. Astrophys. J. 600, 1073.
Zhao, J., Kosovichev, A.G.: 2003, Helioseismic observation of the structure and dynamics of a rotating sunspot beneath the solar surface. Astrophys. J. 591, 446.
Zhao, J., Kosovichev, A.G.: 2006, Surface magnetism effects in time – distance helioseismology. Astrophys. J. 643, 1317.
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Helioseismology, Asteroseismology, and MHD Connections
Guest Editors: Laurent Gizon and Paul Cally.
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Schunker, H., Braun, D.C., Lindsey, C. et al. Physical Properties of Wave Motion in Inclined Magnetic Fields within Sunspot Penumbrae. Sol Phys 251, 341–359 (2008). https://doi.org/10.1007/s11207-008-9142-7
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DOI: https://doi.org/10.1007/s11207-008-9142-7