ChJAA Vol 4, No 5 (2004) / Xu

Visible and Near-Infrared Contrast of Faculae in Active Region NOAA 8518

Yan Xu, Guo Yang, Jiong Qiu, Tom J. Spirock, Ju Jing, Carsten Denker, Haimin Wang

Abstract

We compare the contrast of faculae, in visible light and in the near infrared (NIR), that were associated with the active region NOAA 8518 which crossed the solar disk from April 19 to 27, 1999. We obtained NIR continuum images at 1.6 um at the Big Bear Solar Observatory (BBSO) with an Indium Gallium Arsenide (In Ga As) NIR digital camera. We also obtained high-resolution longitudinal magnetograms and visible light filtergrams at 610.3 nm with the newly developed Digital Vector Magnetograph (DVMG). Our data show that the contrast of faculae has the same sign in both the visible and the NIR. We did not find any so-called ``dark faculae", faculae that are bright in the visible and simultaneously dark in the NIR. We determined a threshold magnetic flux density that separates pores from faculae.

Keywords


Sun: infrared --- Sun: faculae

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