The Swiss Society for Astrophysics and Astronomy organizes each year in the late winter or early spring an advanced course. The format of the school is always iden tical: three leading lecturers are invited to cover the subject in nine or ten lectures each and to deliver a written version of their lecture notes. Lectures are held in the morning and late afternoon, thus leaving ample time for discussion and skiing. These arrangements prove very convivial and lead to an excellent atmosphere in which to learn exciting new subjects and establish contacts with colleagues. A wide variety of people attend the school, including many young students, mostly from Europe, and some experienced researchers. The 20th Advanced Course of the Swiss Society for Astrophysics and Astronomy took place in Les Diablerets from 1 to 6 April 1990. It was devoted to observational and theoretical aspects of active galactic nuclei. The previous advanced courses of the Swiss Society for Astrophysics and Astronomy have regularly taken place in Saas-Fee, a small resort in the Swiss Alps, hence the name "Saas-Fee" used to de scribe the courses and lecture notes. In the last three years, however, the course was organized in Leysin and in Les Diablerets, both also situated in the Swiss Alps."

Active Galactic Nuclei radiate over the electro-magnetic spectrum from radio waves to gamma rays. Understanding the physics of these objects therefore requires the synthesis of results from many different domains of Astronomy. It was the aim of the conference "Active Galactic Nuclei across the Electromagnetic Spectrum" to provide a forum where this exchange could take place. Some 300 astronomers participated to the conference, 250 of them presented results either as oral papers or in the form of posters. Observations in all domains of the electro magnetic spectrum in which astronomical observations can be made from the ground or from space were presented. Many theoretical contributions were also given. There has been a tremendous growth in the number and quality of Astronomical obser vations in many spectral domains over the past several years. Students of Active Galactic Nuclei have been particularly keen to make use of the available facilities (both space born and on the ground), often in a very organised way, in order to obtain repeated simultane ous data covering large bands of the spectrum. This approach has produced a qualitatively new set of data for understanding the physics of Active Galactic Nuclei. The task of the meeting was to review this data in a coherent way."

This volume presents the lecture notes of the 24th Advanced Course of the Swiss Society for Astrophysics and Astronomy in March 1994 at Les Diablerets. In three lectures on magnetohydrodynamics, on kinetic plasma physics and on particle acceleration leading experts describe the physical basis of their subjects and extend the discussion to several applications in modern problems of astrophysics. In style and presentation the texts are well-suited for graduate work in plasma astrophysics, one of the very important tools of modern astronomy. The themes developed in this book will be helpful in understanding many processes in the universe from the solar corona to active galaxies.

This volume presents the lecture notes of the 24th Advanced Course of the Swiss Society for Astrophysics and Astronomy in March 1994 at Les Diablerets. In three lectures on magnetohydrodynamics, on kinetic plasma physics and on particle acceleration leading experts describe the physical basis of their subjects and extend the discussion to several applications in modern problems of astrophysics. In style and presentation the texts are well-suited for graduate work in plasma astrophysics, one of the very important tools of modern astronomy. The themes developed in this book will be helpful in understanding many processes in the universe from the solar corona to active galaxies.

The Swiss Society for Astrophysics and Astronomy organizes each year in the late winter or early spring an advanced course. The format of the school is always iden tical: three leading lecturers are invited to cover the subject in nine or ten lectures each and to deliver a written version of their lecture notes. Lectures are held in the morning and late afternoon, thus leaving ample time for discussion and skiing. These arrangements prove very convivial and lead to an excellent atmosphere in which to learn exciting new subjects and establish contacts with colleagues. A wide variety of people attend the school, including many young students, mostly from Europe, and some experienced researchers. The 20th Advanced Course of the Swiss Society for Astrophysics and Astronomy took place in Les Diablerets from 1 to 6 April 1990. It was devoted to observational and theoretical aspects of active galactic nuclei. The previous advanced courses of the Swiss Society for Astrophysics and Astronomy have regularly taken place in Saas-Fee, a small resort in the Swiss Alps, hence the name "Saas-Fee" used to de scribe the courses and lecture notes. In the last three years, however, the course was organized in Leysin and in Les Diablerets, both also situated in the Swiss Alps."

Active Galactic Nuclei radiate over the electro-magnetic spectrum from radio waves to gamma rays. Understanding the physics of these objects therefore requires the synthesis of results from many different domains of Astronomy. It was the aim of the conference "Active Galactic Nuclei across the Electromagnetic Spectrum" to provide a forum where this exchange could take place. Some 300 astronomers participated to the conference, 250 of them presented results either as oral papers or in the form of posters. Observations in all domains of the electro magnetic spectrum in which astronomical observations can be made from the ground or from space were presented. Many theoretical contributions were also given. There has been a tremendous growth in the number and quality of Astronomical obser vations in many spectral domains over the past several years. Students of Active Galactic Nuclei have been particularly keen to make use of the available facilities (both space born and on the ground), often in a very organised way, in order to obtain repeated simultane ous data covering large bands of the spectrum. This approach has produced a qualitatively new set of data for understanding the physics of Active Galactic Nuclei. The task of the meeting was to review this data in a coherent way."