Issue |
A&A
Volume 365, Number 2, January 2001
|
|
---|---|---|
Page(s) | 186 - 197 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361:20000016 | |
Published online | 15 January 2001 |
Properties of EUV and X-ray emission in solar active regions
1
Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Surrey RH5 6NT, UK
2
Space Science Division, Code 7675, Naval Research Laboratory, Washington, DC 20375-5352, USA
S. A. Matthews
Received:
9
November
1999
Accepted:
5
October
2000
Using observations from the Coronal Diagnostic Spectrometer (CDS) on SoHO and the Soft X-ray Telescope (SXT) on Yohkoh we investigate how the spatial properties of active region emission observed in the EUV and X-ray range varies with temperature. We examine the contrast per unit area of the EUV emission from a number of active regions, and employ correlation techniques and Fourier methods with which we obtain the two dimensional power spectrum of the intensity distribution for a number of images in emission lines formed at different temperatures. Integrating this over polar angle we find isotropic power-law behaviour at all temperatures in a number of topologically different active regions, with a tendency for flatter spectra at lower temperatures. The existence of power-law spectra indicates that there is no preferred length scale within the regions, at least not a resolvable one, while flatter spectra at lower temperatures indicate that the structures are relatively smaller in this temperature range, possibly providing support for the idea of a multi-component transition region (TR). Implications for various heating models are discussed.
Key words: Sun: UV radiation -Sun: Corona -Sun: transition region
© ESO, 2001
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