Influence of magnetic field on the Doppler measurements of velocity field in the solar photosphere and implications for helioseismology
Abstract
Shapes of spectral lines and their sensitivity to fluid motions are strongly altered in magnetised regions of the solar atmosphere. Sunspots and plages (bright network regions) are prime examples. Here we study the temporal behaviour of Ni I (6768 A, used by MDI onboard SOHO) in sunspots and plages using realistic models of sunspots and network flux tubes as input to a radiative transfer code SPINOR (Frutiger et al., 2000) that models spectral line formation in magnetic fields. We examine the sunspot case based on a simple model of oscillations superposed on the Maltby model (empirical) of sunspot atmosphere. The plage regions are studied using a 2-d MHD simulation of oscillatory motions (Hasan et al., 2005) in network flux tubes. We discuss the changes that the altered line profiles would cause in the Doppler measurements of the velocity field, especially those by helioseismic imaging instrument MDI onboard SOHO.
- Publication:
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Proceedings of the ILWS Workshop
- Pub Date:
- 2006
- Bibcode:
- 2006ilws.conf...21R
- Keywords:
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- Sun- helioseismology;
- Sun-magnetic field;
- Sun- oscillations;
- Sun- spectral lines.