Radio Measurements of the Height of Strong Coronal Magnetic Fields Above Sunspots at the Solar Limb

We measure coronal magnetic field strengths of 1750 G at a height of 8000 km above a large sunspot in NOAA AR 10652 at the west solar limb on 2004 July 29 using coordinated observations with the Very Large Array, the Transition Region and Coronal Explorer, and three instruments (CDS, EIT, MDI) aboar...

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Bibliographic Details
Published in:The Astrophysical journal 2006-04, Vol.641 (1), p.L69-L72
Main Authors: Brosius, Jeffrey W, White, Stephen M
Format: Article
Language:English
Subjects:
Astronomy
Earth, ocean, space
Exact sciences and technology
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Summary:We measure coronal magnetic field strengths of 1750 G at a height of 8000 km above a large sunspot in NOAA AR 10652 at the west solar limb on 2004 July 29 using coordinated observations with the Very Large Array, the Transition Region and Coronal Explorer, and three instruments (CDS, EIT, MDI) aboard the Solar and Heliospheric Observatory. This observation is the first time that coronal radio brightness temperatures have been analyzed in a 15 GHz solar radio source projected above the limb. Observations at 8 GHz yield coronal magnetic field strengths of 960 G at a height of 12,000 km. The field strength measurements combine to yield a magnetic scale height L sub(B) = 6900 km. The radio brightness temperature maxima are located away from a sunspot plume that appears bright in EUV line emission formed at temperatures around several x 10 super(5) K. We use the density-sensitive emission-line intensity ratio of O IV 625.8 Ae/554.5 Ae to derive an electron density n sub(e) (in units of cm super(-3)) of log n sub(e) = 10.1 c 0.2 at the base of the plume.
ISSN:1538-4357
0004-637X
1538-4357
DOI:10.1086/503774