The Coronal Magnetic Field, Signatures of Coronal Holes and Silicon Nanometer Dust Grains
Abstract
The near-infrared part of the solar spectrum is where some of the strongest coronal forbidden lines are formed. Polarized emission in these lines offers the only tool currently known for the inference of the direction of the coronal magnetic field. The first successful observations of the polarized emission from the 1074.7 nm Fe XIII line were made by Eddy, Lee and Emerson during the eclipse of 1966 in a limited region of the corona. The only subsequent polarimetric observations in this line were carried out with the coronagraph at Sac Peak from 1977-1980. We report on the first successful polarimetric measurements of the 1074.7 nm line in a field of view extending out to 3.5 solar radii which were made during the total solar eclipse of 21 June 2001. In addition to confirming earlier results of the predominance of a radial direction of the coronal magnetic field, these measurements yielded the first polarimetric signature of coronal holes, and the signature of nanometer size dust grains in the corona. These observations suggest the existence of a rich coronal spectrum of narrow lines in the near-infared produced by the fluorescence of silicon nanometer dust grains in the inner corona. This work was funded by NSF grant ATM-0003661 and NASA grant NAG5-10873 to the Smithsonian Astrophysical Observatory.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2003
- Bibcode:
- 2003AGUFMSH41D..04H
- Keywords:
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- 2129 Interplanetary dust;
- 2169 Sources of the solar wind;
- 7509 Corona;
- 7511 Coronal holes;
- 7524 Magnetic fields