Surface magnetic field effects in local helioseismology

✍ Scribed by H. Schunker; D. C. Braun; P. S. Cally

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 690 KB
• Volume: 328
• Category: Article
• ISSN: 0004-6337
• DOI: 10.1002/asna.200610732

✦ Synopsis

Abstract

Using helioseismic holography strong evidence is presented that the phase (or equivalent travel‐time) of helioseismic signatures in Dopplergrams within sunspots depend upon the line‐of‐sight angle in the plane containing the magnetic field and vertical directions. This is shown for the velocity signal in the penumbrae of two sunspots at 3, 4 and 5 mHz. Phasesensitive holography demonstrates that they are significantly affected in a strong, moderately inclined magnetic field. This research indicates that the effects of the surface magnetic field are potentially very significant for local helioseismic analysis of active regions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)