This thesis would not have been possible without the contributions of a large
number of individuals. In particular, I would like to express my deep gratitude
to my supervisor Prof. Dr. Jürgen H.M.M. Schmitt, who provided me with
excellent support during the course of this work. I especially appreciate his
valuable advice and his bright spirit providing me with a lot of enthusiasm.
In addition, he patronized my scientific career with his readiness to let me
benefit from his excellent connections and his broad experience.
It was always a great pleasure to discuss with Dr. Vadim Burwitz, and I appreciate his generosity in every concern. Particularly, his help in reducing the Chandra LETGS data providing me with most useful data was an essential element of this work.
A lot of experience in programming, Linux, ANSI C, GUI programming, etc., I owe to Dr. Rainer Wichmann, a pleasant fellow and room-mate, whose reliability and experience, but also his special character were of high value for me. I appreciate his contribution to the CORA program and to Chapter 2, and the collaboration in this project was very fruitful.
Dr. Matthias Hünsch gave me the idea to work with Jürgen Schmitt. I never regretted to follow his advice. I appreciate that he carried me through critical times during the work, and his careful reading of my thesis.
During my visit to Utrecht, Dr. Rolf Mewe cared for me with important insights into SRON, the Space Research Organization of the Netherlands, and provided me with interesting data, which enabled me to work out results presentable to the scientific community.
An important aspect to mention is the cooperation with my co-authors in the publications who contributed to the work with ideas and criticism, which helped to improve the results. Special thanks to the principal investigators of the instruments. Without their efforts, no scientific work would be possible.
My colleagues Dr. Rainer Wichmann, Dr. Marc Hempel, Ansgar Reiners, Birgit Fuhrmeister, and Nadine Nettelmann gave me valuable corrections for wording, grammar, and helped me to remove a tremendous number of obsolete commas.
I thank Marc Audard for careful reading with useful ideas, and Dr.
Manuel Güdel for useful discussion and contributing with Fig. 1.5.
All work is not possible without good friends. I am glad that I have a number of friends, and I would like to mention my closest friends Markus Götze, Volkmar Niemann, and Reinhold Bussmann, who also supported this work with his experience in grammar and language.
Special thanks to my parents, who taught me the ambition and the
idealism to stay the course through this work.
I acknowledge financial support from Deutsches Zentrum für Luft- und
Raumfahrt e.V. ( DLR) under 50OR98010.