The Imaging Vector Magnetograph at Haleakalā IV: Stokes Polarization Spectra in the Sodium D1 589.6 nm Spectral Line
The Imaging Vector Magnetograph (IVM) at the Mees Solar Observatory, Haleakalā, Maui, Hawai’i, obtained many years of vector magnetic-field data in the photospheric Fe i 630.25 nm line. In the latter period of its operation, the IVM was modified to allow routine observations in the chromospheric Na i D1 line, as well as the Fe i line. We describe the sodium observational data in detail, including the data-reduction steps that differ from those employed for the Fe i 630.25 nm line, to obtain calibrated Stokes polarization spectra. We have performed a systematic comparison between the observational data and synthetic NLTE Na i D1 Stokes spectra derived for a variety of solar-appropriate atmospheric and magnetic configurations. While the Na i D1 Stokes polarization signals from the solar atmosphere are expected to be weak, they should generally be within the IVM capability. A comparison between synthetic spectra and observational data indicates that this is indeed the case.
KeywordsSun: chromosphere Observations Polarimetry Data analysis
We thank G. Nitta for his deft handling of the IVM operations, and distinctly remember an additional colleague whose vision and effort were fundamental to the IVM’s mission: Dr. Barry LaBonte. We also thank Dr. Richard C. Canfield for enabling the Imaging Vector Magnetograph to get funded and built; we acknowledge NASA grant NAGW-1454 and NSF ATM 8813157 for the IVM’s construction. We thank the referee for help clarifying the text and presentation. The work on Na i D1 data was supported by NASA grant NAG5-12466 and contract No. NNH09CE60C, by AFOSR contract F49620-03-C-0019, NSF National Space Weather Program Grant No. ATM-0519107, NSF SHINE grants ATM-0454610 and NSF Collaborative Research Grant ATM-0551055.
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