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Measurements of solar magnetic fields by Fourier transform techniques

II. Saturated and blended lines

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Abstract

The Fourier techniques of Paper I have been exhaustively calibrated using Unno's results for the absorption profile of a simple Zeeman triplet. If a simple transformation is applied to the normalized line depths, then magnetic field strengths and inclination angles can be measured very accurately from noisy, saturated line profiles. Systematic errors caused by saturation effects can be estimated and reduced by varying one parameter. When a significant fraction of the line profile is unsplit and unpolarized, large errors may be made in measurements of low fields, unless the line is sufficiently weak. For a weak line, a vertical field of 1600 gauss can be measured to 10% accuracy even when 70% of the line profile is stray light. These stray light errors are troublesome in measuring fields of gaps and pores but not sunspots. Numerical results of our error analysis are presented graphically.

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References

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Authors and Affiliations

  1. Lockheed Palo Alto Research Laboratory, 94304, Palo Alto, Calif., U.S.A.

    Theodore D. Tarbell & Alan M. Title

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  1. Theodore D. Tarbell
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  2. Alan M. Title
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Tarbell, T.D., Title, A.M. Measurements of solar magnetic fields by Fourier transform techniques. Sol Phys 47, 563–573 (1976). https://doi.org/10.1007/BF00154765

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  • DOI: https://doi.org/10.1007/BF00154765

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