Fludra, Andrzej

Contact Email: fludra@cdso8.nascom.nasa.gov
Institute: Rutherford Appleton Laboratory, Chilton,
Didcot, OX11 0QX, UK
First Coauthor: Jack Ireland
Institute: Osservatorio Astronomico di Capodimonte,
Napoli, Italy
Subject Area: The Sun
Waveband: Extreme Ultraviolet
Technique: Spectroscopy
Presentation: Oral Contribution: Tuesday
Title: The Magnetic Field and EUV Line Intensities in Solar Active Regions
Abstract: Relationships between the photospheric magnetic flux and intensities of spectral lines emitted from the solar atmosphere have been extensively studied by several authors. Power-law relations have been found between the total magnetic flux and total intensities of the chromospheric, transition region and coronal emission lines in active regions. We extend the previous work by using Extreme Ultraviolet lines recorded by the Coronal Diagnostic Spectrometer on SOHO for 50 solar active regions, as they crossed the central meridian in years 1996-1998. We use four spectral lines: He I 584.3 Å ( $2\times 10^4$ K), O V 629.7 Å ( $2.2 \times 10^5$ K), Mg IX 368.06 Å ( $9.5 \times 10^5$ K), and Fe XVI 360 Å ( $2 \times 10^6$ K). In particular, the Fe XVI 360 Å line, seen only in areas of enhanced heating in active regions or bright points, has not been used before for this analysis. We establish empirical relations among intensities of those four lines, and between the total active region line intensity and the total magnetic flux. The dependence of the coronal loop heating rate on the magnetic flux density is derived and its implications for the coronal heating models are discussed.