Reuven Ramaty, a pioneer in high energy astrophysics, died of complications from amyotrophic lateral sclerosis, or Lou Gehrig's disease, at his home in Silver Spring, Maryland, on 8 April 2001. Undaunted by the ravages of his illness, he was still studying new cosmic ray data in his last hours. He is survived by his wife, Vera, his two daughters, Daphne and Deborah, and five grandchildren.
Reuven was born on 25 February 1937, in Timisoara, a Hungarian enclave in Romania. He grew up during the strife of World War II, and immigrated with his parents to Israel in 1948, graduating from Tel Aviv University in 1961 with a BSc in Physics. He taught high school physics for three years, before coming to the University of California at Los Angeles, where he earned his PhD in Planetary and Space Physics in 1966, in a record time of two years. Reuven joined the NASA Goddard Space Flight Center in 1967 and remained for over 30 years, becoming one of its leading theorists. He was the head of the Theory Office at the center from 1980 to 1993. Since 1983 he was also an Adjunct Professor of Physics at the University of Maryland, where he was an advisor for six PhD students. Reuven also served on doctoral dissertation committees at the University of Paris and the Pierre & Marie Curie University in Paris.
Reuven had a profound impact on solar flare physics, gamma-ray astronomy and cosmic rays. This is reflected in over 200 publications and more than 5,000 citations to his work in the literature. He is probably best known for his work on solar flare particle interactions. He and I first showed in 1967 that gamma ray line and neutron measurements from flares could be a powerful diagnostic for determining the properties of flare-accelerated particles. In later expanded collaborations, with Benz Kozlovsky of Tel Aviv University and others, Reuven continued to refine these techniques. Their extensive studies of flare measurements from the Solar Maximum Mission and the Compton Gamma Ray Observatory probed particle acceleration mechanisms and both accelerated particle and coronal abundances. Colleagues point out that NASA's recent High Energy Solar Spectroscopic Imager (HESSI) mission might not have been realized without Reuven's active encouragement and involvement. With Len Fisk of the University of New Hampshire and Benz Kozlovsky, Reuven further proposed the now generally accepted origin of low energy "anomalous cosmic rays" from the ionization and acceleration of neutral interstellar gas in the outer heliosphere.
Reuven was also a pioneer in gamma-ray-line astronomy, carrying out seminal studies of positron annihilation radiation, nuclear de-excitation lines and nucleosynthetic decay lines in the interstellar medium and in compact sources. Much of this work was summarized in a review of "Gamma Ray Lines: A New Window to the Universe" in Physics Today in 1978. The most notable of these studies was the prediction of interstellar gamma-ray emission in the 1.809 MeV line from the decay of supernova- produced26 A1. This emission was subsequently discovered with instruments on HEAO-C in 1982. It proved to be the most intense nucleosynthetic line in the interstellar medium. Most recently, Reuven and his colleagues showed that observations of the early stellar abundances of cosmic-ray-produced Be and B required that Galactic cosmic rays had to be accelerated in high metallicity material and not out of the average interstellar medium as was generally supposed. This work was also presented in a Physics Today review in 1998 on "Cosmic Rays, Nuclear Gamma Rays and the Origin of Li, Be and B."
Reuven served the high-energy astronomy community as Chairman of the High-Energy Astronomy Division of the American Astronomical Society; Chairman of the Division of Astrophysics and Divisional Councilor for Astrophysics, of the American Physical Society; and an Associate Editor of Physical Review Letters. In addition, he organized several conferences, authored numerous review articles, and gave many invited talks worldwide. He was a visiting scientist at Caltech, Stanford University, University of California (Berkeley and San Diego), University of Pennsylvania, Washington University in St. Louis, and Nagoya University in Japan.
Just a week before he died, Reuven was awarded the first Yodh Prize for lifetime achievement from the International Cosmic Ray Conference. This climaxed earlier awards and recognition, including "A Tribute to Reuven Ramaty's Contributions to High-Energy Solar Physics and Astronomy" held by the University of Maryland on 11 December 2000; the Exceptional Scientific Achievement Medal from NASA in 1981; the Lindsay Award in 1980 for his work on the theory of gamma-ray repeaters; and a Senior US Scientist Award from the Alexander von Humboldt Foundation in 1975.
Reuven will be dearly missed by his many friends and collaborators.
Photograph courtesy of Vera Ramaty