X- and XUV-radiation of the solar corona

First a survey of the ionization states and emission lines of the ions existing in the corona is given. Then instruments for taking pictures of the Sun in the X- and the XUV-region as well as for measuring spectra emitted in interesting locations on the Sun are presented. Methods of plasma diagnostics, in particular for the determination of the mean temperature and the differential emission measure are described.In the following review of observations, which are related to the topic of the workshop, types of coronal structures especially coronal holes, active regions and large scale structures are described. Their relations to the photospheric magnetic fields are dealt with; methods to calculate coronal magnetic fields are briefly discussed. As for temporal variations results of the analysis of expanding X-ray arches and of structures becoming visible in the outer corona in white light are mentioned. Finally, plasma diagnostics by means of high-resolution spectra are dealt with, in particular methods for the determination of the particle density by lines of He-like ions and of the local temperature by Li-like satellites lines. Thus non-thermal random velocities and outward moving plasma can be inferred during flares.Paper presented at the IX-th Lindau Workshop The Source Region of the Solar Wind.