ORIGIN, INJECTION, AND ACCELERATION OF CIR PARTICLES: OBSERVATIONS Report of Working Group 6 G. M. MASON 1 AND R. VON STEIGER 2 CO-CHAIRS R. B. DECKER 3 , M. I. DESAI 1 , J. R. DWYER 1 , L. A. FISK 4 , G. GLOECKLER 14 , J. T. GOSLING 5 , M. HILCHENBACH 6 , R. KALLENBACH 2 , E. KEPPLER 6 , B. KLECKER 7 , H. KUNOW 8 , G. MANN 9 , I. G. RICHARDSON 1 10 , T. R. SANDERSON 11 , G. M. SIMNETT 12 , Y.-M. WANG 13 , AND R. F. WIMMER-SCHWEINGRUBER 14 PARTICIPANTS M. FRÄNZ 15 AND J. E. MAZUR 16 CONTRIBUTING AUTHORS NOT PARTICIPATING IN THE WORKSHOP 1 Dept. of Astronomy and IPST, University of Maryland, College Park, Maryland, USA 2 International Space Science Institute, Bern, Switzerland 3 Applied Physics Laboratory, John Hopkins University, Laurel, Maryland, USA 4 Dept. of Atmospheric and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA 5 Los Alamos National Laboratory, Los Alamos, New Mexico, USA 6 Max-Planck-Institut für Aeronomie, Katlenburg-Lindau, Germany 7 Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany 8 Extraterrestrische Physik, Universität Kiel, Kiel, Germany 9 Astrophysikalisches Institut, Potsdam, Germany 10 NASA Goddard Space Flight Center, Greenbelt, Maryland, USA 11 Space Science Dept. of ESA/ESTEC, Noordwijk, The Netherlands 12 Physics and Astronomy Dept., University of Birmingham, Birmingham, United Kingdom 13 E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DC, USA 14 Physikalisches Institut der Universität Bern, Bern, Switzerland 15 Queen Mary and Westfield College, London, United Kingdom 16 Aerospace Corporation, Los Angeles, California, USA Received: 4 November 1998; Accepted: 25 May 1999 Abstract. This report emphasizes new observational aspects of CIR ions revealed by advanced instruments launched on the Ulysses, WIND, SOHO, and ACE spacecraft, and by the unique van- tage point of Ulysses which carried out the first survey of Corotating Interaction Region (CIR) properties over a very wide range of heliolatitudes. With this more complete observational picture established, this review is the basis to consider the status of theoretical models on origin, injection, and acceleration of CIR particles reported by Scholer, Mann et al. (1999) in this volume. Space Science Reviews 89: 327–367, 1999. c 1999 Kluwer Academic Publishers. Printed in the Netherlands.