This textbook is intended as an introduction to the physics of solar and stellar coronae, emphasizing kinetic plasma processes. It is addressed to observational astronomers, graduate students, and advanced undergraduates without a ba- ground in plasma physics. Coronal physics is today a vast field with many different aims and goals. So- ing out the really important aspects of an observed phenomenon and using the physics best suited for the case is a formidable problem. There are already several excellent books, oriented toward the interests of astrophysicists, that deal with the magnetohydrodynamics of stellar atmospheres, radiation transport, and radiation theory. In kinetic processes, the different particle velocities play an important role. This is the case when particle collisions can be neglected, for example in very brief phenomena - such as one period of a high-frequency wave - or in effects produced by energetic particles with very long collision times. Some of the most persistent problems of solar physics, like coronal heating, shock waves, flare energy release, and particle acceleration, are likely to be at least partially related to such p- cesses. Study of the Sun is not regarded here as an end in itself, but as the source of information for more general stellar applications. Our understanding of stellar processes relies heavily, in turn, on our understanding of solar processes. Thus an introduction to what is happening in hot, dilute coronae necessarily starts with the plasma physics of our nearest star.

Continuum radio emission and fine structure (in particular millisecond spikes) have recently raised interest as diagnostic tools for the interpretation of energy release and particle acceleration in flares. In the circles of the European solar radio astronomers, loosely organized in CESRA, the idea of a workshop came up intended for active observers of the impulsive phase of flares in radio and associated emissions. The scientific organizing committee included A.D. Benz (chairman), A. Magun, M. Pick, G. Trottet, and P. Zlobec. The workshop was held on May 27-31, 1985 in the castle of Duino near Trieste, Italy. The meeting intended to find a common terminology, to compare radio observations with measurements in other emissions and to confront observations with theoretical concepts. We have achieved a representative summary on the current status of the field and a clear perspective for the next cycle. This volume contains the reviews and a selection of contributions and extended abstracts of papers presented at the workshop. I wish to thank the local organizers, in particular A. Abrami, M. Comari, F. Depolli, L. Fornasari, M. Messerotti (chairman), M. Nonino, and P. Zlobec. Financial support was graciously provided by the Italian Research Council (CNR). Most of all, however, I would like to express my thankfulness to our host, His Highness Prince Raimondo della Torre e Tasso, for his invaluable hospitality. We are deeply sorry to hear of his passing in the meantime. To his memory these proceedings are dedicated.

This textbook is a basic introduction to kinetic plasma phenomena in solar and stellar coronae. The author unifies observations and theory which gives a wide perspective to the subject. An important feature is the lucidly written presentation of the fundamentals of plasma physics. The basic theory developed is then extended to some exemplary and important observations of coronal dynamics, such as coronal current, particle acceleration, propagation of particle beams, and shocks. The book has grown from the author's introductory courses on plasma astrophysics at the Swiss Federal Institute of Technnology (ETH). It is aimed at advanced undergraduates and first-year graduate students without a background in plasma physics. It should also be of interest to more senior research workers involved in coronal physics, solar/stellar winds, and various other fields of plasma astrophysics. Problems suitable for class use are included at the end of each chapter.

The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) satellite was launched on 5 February 2002. Its objective is to study the energy release and particle acceleration in solar flares through observations of X-rays and gamma rays. Two novel technologies are combined to obtain both spectra and images over a broad energy range. For the spectroscopy, cooled hyperpure germanium detectors are used to cover the energy range from 3 keV to 17 MeV with unprecedented keV-class resolution. Since focusing optics are not possible for making images with such high energy photons, tungsten and molybdenum absorbing grids are used to modulate the X-rays and gamma-rays coming from the Sun as the spacecraft rotates. This allows the spatial Fourier components of the source to be determined so that images can be made in spectral ranges where astronomical images have never been produced before. These new instrumental techniques require equally innovative software to reconstruct X-ray and gamma-ray spectra and images from the observations.

Ample solar activity, abundant observations, and an open data policy have attracted many researchers. Astronomers face in the RHESSI mission an exciting new scientific potential. It has unusually broad possibilities for improving our understanding of the enigmatic solar flare phenomenon that is becoming increasingly important as society depends more and more on space-based technologies.
In this volume, the functioning of RHESSI is explained, the data analysis techniques including spectroscopy and image reconstruction are introduced, and the experiences of the first few months of operation are summarized. First scientific results are presented thatprovide the essential base for more extended studies using RHESSI data and complementary observations by instruments on other spacecraft and at ground-based solar observatories.

The accompanying CD-ROM contains X-ray and EUV movies showing the dynamics of several solar flares. It also contains color versions of the graphics in the printed papers and additional material.

Scientists and students will find here the latest discoveries in solar flare research, as well as inspiration for future work. The papers will serve as references for the many new discoveries to come from the continuing RHESSI observations.

This textbook is intended as an introduction to the physics of solar and stellar coronae, emphasizing kinetic plasma processes. It is addressed to observational astronomers, graduate students, and advanced undergraduates without a ba- ground in plasma physics. Coronal physics is today a vast field with many different aims and goals. So- ing out the really important aspects of an observed phenomenon and using the physics best suited for the case is a formidable problem. There are already several excellent books, oriented toward the interests of astrophysicists, that deal with the magnetohydrodynamics of stellar atmospheres, radiation transport, and radiation theory. In kinetic processes, the different particle velocities play an important role. This is the case when particle collisions can be neglected, for example in very brief phenomena - such as one period of a high-frequency wave - or in effects produced by energetic particles with very long collision times. Some of the most persistent problems of solar physics, like coronal heating, shock waves, flare energy release, and particle acceleration, are likely to be at least partially related to such p- cesses. Study of the Sun is not regarded here as an end in itself, but as the source of information for more general stellar applications. Our understanding of stellar processes relies heavily, in turn, on our understanding of solar processes. Thus an introduction to what is happening in hot, dilute coronae necessarily starts with the plasma physics of our nearest star.

This book brings together a variety of review articles on dynamical phenomena in the solar corona in order to work out the unifying aspects of magnetic energy releases. The experimental data from groundbased methods of radio astronomy as well as from satellites are also discussed. The book addresses researchers in astrophysics, and planetary science but should also be accessible to graduate students.

Continuum radio emission and fine structure (in particular millisecond spikes) have recently raised interest as diagnostic tools for the interpretation of energy release and particle acceleration in flares. In the circles of the European solar radio astronomers, loosely organized in CESRA, the idea of a workshop came up intended for active observers of the impulsive phase of flares in radio and associated emissions. The scientific organizing committee included A.D. Benz (chairman), A. Magun, M. Pick, G. Trottet, and P. Zlobec. The workshop was held on May 27-31, 1985 in the castle of Duino near Trieste, Italy. The meeting intended to find a common terminology, to compare radio observations with measurements in other emissions and to confront observations with theoretical concepts. We have achieved a representative summary on the current status of the field and a clear perspective for the next cycle. This volume contains the reviews and a selection of contributions and extended abstracts of papers presented at the workshop. I wish to thank the local organizers, in particular A. Abrami, M. Comari, F. Depolli, L. Fornasari, M. Messerotti (chairman), M. Nonino, and P. Zlobec. Financial support was graciously provided by the Italian Research Council (CNR). Most of all, however, I would like to express my thankfulness to our host, His Highness Prince Raimondo della Torre e Tasso, for his invaluable hospitality. We are deeply sorry to hear of his passing in the meantime. To his memory these proceedings are dedicated.

This textbook is intended as an introduction to the physics of solar and stellar coronae, emphasizing kinetic plasma processes. It is addressed to observational astronomers, graduate students, and advanced undergraduates without a back ground in plasma physics. Coronal physics is today a vast field with many different aims and goals. Sort ing out the really important aspects of an observed phenomenon and using the physics best suited for the case is a formidable problem. There are already several excellent books, oriented toward the interests of astrophysicists, that deal with the magnetohydrodynamics of stellar atmospheres, radiation transport, and radiation theory. In kinetic processes, the different particle velocities play an important role. This is the case when particle collisions can be neglected, for example in very brief phenomena - such as one period of a high-frequency wave - or in effects produced by energetic particles with very long collision times. Some of the most persistent problems of solar physics, like coronal heating, shock waves, flare energy release, and particle acceleration, are likely to be at least partially related to such pro cesses. Study of the Sun is not regarded here as an end in itself, but as the source of information for more general stellar applications. Our understanding of stellar processes relies heavily, in turn, on our understanding of solar processes. Thus an introduction to what is happening in hot, dilute coronae necessarily starts with the plasma physics of our nearest star.

The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) satellite was launched on 5 February 2002. Its objective is to study the energy release and particle acceleration in solar flares through observations of X-rays and gamma rays. Two novel technologies are combined to obtain both spectra and images over a broad energy range. For the spectroscopy, cooled hyperpure germanium detectors are used to cover the energy range from 3 keV to 17 MeV with unprecedented keV-class resolution. Since focusing optics are not possible for making images with such high energy photons, tungsten and molybdenum absorbing grids are used to modulate the X-rays and gamma-rays coming from the Sun as the spacecraft rotates. This allows the spatial Fourier components of the source to be determined so that images can be made in spectral ranges where astronomical images have never been produced before. These new instrumental techniques require equally innovative software to reconstruct X-ray and gamma-ray spectra and images from the observations.
Ample solar activity, abundant observations, and an open data policy have attracted many researchers. Astronomers face in the RHESSI mission an exciting new scientific potential. It has unusually broad possibilities for improving our understanding of the enigmatic solar flare phenomenon that is becoming increasingly important as society depends more and more on space-based technologies.
In this volume, the functioning of RHESSI is explained, the data analysis techniques including spectroscopy and image reconstruction are introduced, and the experiences of the first few months of operation are summarized. First scientific results are presented that provide the essential base for more extended studies using RHESSI data and complementary observations by instruments on other spacecraft and at ground-based solar observatories.Scientists and students will find here the latest discoveries in solar flare research, as well as inspiration for future work. The papers will serve as references for the many new discoveries to come from the continuing RHESSI observations.