Spectral line selection for HMI

Norton , A.A., Pietarila Graham, J.D., Ulrich, R.K., Schou, J. , Tomczyk, S., Liu, Y. , Lites, B.W., Ariste, A. Lopez, Bush , R.I., Socas-Navarro, H. , and Scherrer, P.H. (2006) Spectral line selection for HMI. In: Proceedings of Astronomical Society of the Pacific Conference Series (358) pp. 193-196. From: Astronomical Society of the Pacific Conference Series, 19-23 September 2006, Colorado, USA.

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We present information on two spectral lines, Fe I 6173 Å and Ni I 6768 Å, that were candidates for use in the Helioseismic and Magnetic Imager (HMI) instrument. Both Fe I and Ni I profiles have clean continuum and no blends that threaten performance. The higher Landé factor of Fe I means its operational velocity range in regions of strong magnetic field is smaller than for Ni I. Fe I performs better than Ni I for vector magnetic field retrieval. Inversion results show that Fe I consistently determines field strength and flux more accurately than the Ni I line. Inversions show inclination and azimuthal errors are recovered to ≈ 2° above 600 Mx/cm2 for Fe I and above 1000 Mx/cm2 for Ni I. The Fe I line was recommended, and ultimately chosen, for use in HMI.

Item ID: 9644
Item Type: Conference Item (Research - E1)
ISBN: 978-1-58381-292-1
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Date Deposited: 14 Apr 2010 23:41
FoR Codes: 02 PHYSICAL SCIENCES > 0201 Astronomical and Space Sciences > 020109 Space and Solar Physics @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970102 Expanding Knowledge in the Physical Sciences @ 100%
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