Astron. Astrophys. Suppl. Ser. 143, 227-263
Comparison of 87 GHz solar polar structures with EUV and soft X-ray emission
Send offprint request: S. Pohjolainen,
1 - DASOP, Observatoire de Paris, Meudon, France
2 - Metsähovi Radio Observatory, Helsinki Univ. of Technology, Espoo, Finland
3 - Equipe SOHO/EIT, Laboratoire d'Astronomie Spatiale, LAS-CNRS, Marseille, France
4 - DEA, Observatoire de Paris, Meudon, France
Received April 21, 1999; accepted January 21, 2000
The observed radio depressions near the solar poles were very well correlated with coronal holes and other EUV and/or soft X-ray intensity drops. More than half of the coronal holes, or coronal hole-like intensity drops in EUV and soft X-rays, had radio brightenings inside them. Therefore coronal holes do not have uniform radio brightness at 87 GHz.
Many of the bright points seen at lower latitudes in the EIT and SXT images had no, or just faint, counterparts in the millimeter radio maps. It appears that for an EUV bright point to show up at 87 GHz it has to be bright and/or spatially large also in soft X-rays.
Key words: Sun: chromosphere -- Sun: transition region -- Sun: corona -- Sun: radio radiation -- Sun: UV radiation -- Sun: X-rays