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Astron. Astrophys. 338, 1102-1108 (1998)

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The solar transition region:
a time-varying interface between the chromosphere and corona?

E. O'Shea 1, J.G. Doyle 2 and F.P. Keenan 1

1 Department of Pure & Applied Physics, The Queen's University of Belfast, Belfast BT7 1NN, N.Ireland, UK (E.Oshea@queens-belfast.ac.uk; F.Keenan@queens-belfast.ac.uk)
2 Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland, UK (jgd@star.arm.ac.uk)

Received 20 May 1998 / Accepted 5 August 1998


Using joint observations taken with the CDS and SUMER instruments onboard SOHO, we re-examine the solar transition region in an attempt to determine whether it is de-coupled from the over-lying coronal region. Line ratios calculated from temporal series observations of O IV and Fe XIII spectral lines were converted to electron density, and hence electron pressure using theoretical line ratios. Little or no evidence was found to support the constant electron density assumption, and instead a constant electron pressure is found between the transition region and corona. This lends support to the idea that the transition region is a time varying interface between the chromosphere and corona, and is not formed in unresolved fine-structures that are disconnected from the corona.

Key words: atomic data – Sun: transition region – Sun: corona – Sun: UV radiation

Send offprint requests to: E. O'Shea

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© European Southern Observatory (ESO) 1998

Online publication: September 17, 1998