Other
Scientific paper
Oct 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999esasp.446..287c&link_type=abstract
8th SOHO Workshop: Plasma Dynamics and Diagnostics in the Solar Transition Region and Corona. Proceedings of the Conference hel
Other
Scientific paper
In the present work we show that EUV and radio observation can provide a very powerful plasma diagnostics when combined together. The intensity of EUV lines formed in the range of temperature corresponding to the Chromosphere-Corona Transition Region, supplies the DEM function defined as DEM(T)=Ne2 dh/dT. Above the temperature where no more lines are detected, the DEM can be either truncated or arbitrarily extrapolated to a very low value at a very high temperature. The DEM derived with both assumptions reproduce of course very well the observed line intensities, being derived from a best fit of these lines. We have used the DEM, derived from a set of EUV lines observed by CDS in an equatorial Coronal Hole using both assumptions, to compute the radio brightness temperature. The comparison of the computed Tb with the values observed by the Nancay Radiheliograph in the same hole, shows that both DEM assumptions are unable to reproduce the observations and that it is necessary to add the contribution of an isothermal Corona above the region where the DEM is defined. From the fit of the radio observations at four frequencies between 164 and 410 MHz, the coronal hole Emission Measure and an upper limit of the coronal electron temperature (T < 9. 105) are derived. Using this coronal model, together with the DEM up to T < 9.105, we have computed the theoretical EUV line intensities, obtaining a very good agreement with the observations for T > 8x105 K, thus providing also a lower limit to the hole temperature.
Chiuderi Drago Franca
Delouis Jean-Marc
Fludra Andrzej
Kerdraon Alain
Landi Enrico
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