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Astron. Astrophys. 340, 265-276 (1998)

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Temperature and density diagnostics of quiet Sun and active regions observed with CDS NIS

E. Landi 1 and M. Landini 1

1 Department of Astronomy and Space Science, University of Florence, Italy

Received 19 February 1998 / Accepted 15 September 1998

Abstract

We study the Differential Emission Measure distribution of two pairs of active and quiet regions of the solar atmosphere, observed by CDS Normal Incidence Spectrometer (NIS) on SOHO, and investigate their temperature and density structure . Use is made of the Arcetri Method (Landi & Landini 1997) for DEM and density diagnostics. An iterative method for determining the DEM is presented; it allows to select physically meaningful DEM distributions having a definite top temperature along the line of sight. Density sensitive lines are identified and density diagnostics is performed for all the four different spectra. Comments are made on the density versus temperature curves obtained for each region. Simple constant pressure models are not satisfactory and constraints on temperature and density distributions are discussed.

Key words: Sun: activity – Sun: atmosphere – Sun: corona – Sun: UV radiation

Send offprint requests to: E. Landi

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© European Southern Observatory (ESO) 1998

Online publication: November 3, 1998
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