A Themed Issue in Honor of Professor Reinhard Schlickeiser on the Occasion of His 70th Birthday

This Special Issue is dedicated to Professor Reinhard Schlickeiser on the occasion of his 70th birthday. Reinhard Schlickeiser's internationally well-recognized work, comprising several hundred research articles and the comprehensive monograph "Cosmic Ray Astrophysics," has had a lasting influence in several areas of astrophysics. He has also inspired a large number of junior researchers, many of whom are now pursuing successful academic careers. Over the last few decades, he has motivated and established many fruitful collaborations that have triggered new ideas and provided new insights into various plasma and astrophysical topics. This Special Issue aims to present original papers by Reinhard Schlickeiser's collaborators that document the breadth of his scientific accomplishments and the subsequent studies that he has directly or indirectly influenced as a collaborator or as a teacher. This Special Issue may serve as inspiration for others to follow in his path and to accept the challenges awaiting them in the many areas of astrophysics that have been, for many years, Reinhard's turf.