The Magnetic Field and EUV Line Intensities in
Solar Active Regions
A. Fludra & J. Ireland
Institute: Rutherford Appleton Laboratory
Institute: NASA Goddard Space Flight Center
Contact Email: fludra@cdso8.nascom.nasa.gov
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. This approach is applied to extreme ultraviolet lines
recorded by the Coronal Diagnostic Spectrometer (CDS) on SOHO for 50
solar active regions, as they crossed the central meridian in years
1996-1998. Four spectral lines are examined: He I 584.3 A (2 x
10^4 K), O V 629.7 A (2.2 x 10^5 K), Mg IX 368.06 A
(9.5 x 10^5 K), and Fe XVI 360.76 A (2.0 x
10^6 K). In particular, the Fe XVI 360.76 A line, seen only in
areas of enhanced heating in active regions or bright points, has not
been used before for this analysis. Empirical relations are
established between the total active region intensity in Fe XVI and
O V lines, and the total magnetic flux and between the
spatially-averaged intensities and the magnetic flux density. 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.
Index Keywords: Sun ; Active Regions; Corona ; Transition Region ;
Coronal Heating ; Magnetic Field ; EUV Emission
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Manuscript submitted: 2001-Sep-5
"The Future of Cool-Star Astrophysics", 2003, Eds. A. Brown,
G. M. Harper, & T. R. Ayres.
Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems,
& The Sun,
© 2003 University of Colorado.