Spectral Line Selection for HMI

Bibcode
2006ASPC..358..193N
Norton, A. A.; Pietarila Graham, J. D.; Ulrich, R. K.; Schou, J.; Tomczyk, S.; Liu, Y.; Lites, B. W.; López Ariste, A.; Bush, R. I.; Socas-Navarro, H.; Scherrer, P. H.
Bibliographical reference

Solar Polarization 4, ASP Conference Series, Vol. 358, Proceedings of the conference held 19-23 September, 2005, in Boulder, Colorado, USA. Edited by R. Casini and B. W. Lites, p.193

Advertised on:
12
2006
Number of authors
11
IAC number of authors
0
Citations
3
Refereed citations
2
Description
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 Ne 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.
Type
Non-refereed

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