Donald Arnush, Adjunct Professor at UCLA, succumbed to cancer on April 24, 2003.

A 1961 graduate of M.I.T., Arnush afterwards went to Germany and studied under Heisenberg. His career in theoretical physics started in space, with polar and auroral electrojets, later going to parametric instabilities and laser theory.

He was employed at TRW, Inc., in Manhattan Beach, California, where he worked on missile and military satellite programs. There he made major contributions to problems dealing with EMP (Electromagnetic Pulses), underwater communication, and high-intensity light propagation through the atmosphere. He successfully tackled the problem of the effect of an intense gamma ray burst on the atmosphere and on underground weapons. His work on the scattering of blue-green light by a turbulent medium led to a scheme for detection of clear-air turbulence. To treat nonlinear plasma effects of intense laser beams in air, he invoked Raman scattering well before this became a problem in laser fusion.

In the 1970s Arnush was the scientific director of the PSP project at TRW, in which the Dawson Isotope Separation method was developed and applied successfully to pure uranium plasmas. In this capacity, he supervised the writing of ANTENA, a code for excitation of radiofrequency waves, which is often used in ion cyclotron heating. The principal instigators and leaders of the PSP project, John Dawson, Burt Fried, and now Don Arnush, are no longer with us. In the 1980s, he rose to Manager of the Applied Physics Lab at TRW and to Assistant Manager of the Electro-Optics Technology and Applied Physics Center, initiating projects on high-power microwave sources, free electron lasers, and ion sources for neutral beams.

After retiring from TRW in 1994, Arnush continued to work in plasma physics, since he considered physics to be his main hobby. He taught a course on Plasma Waves and Instabilities in the UCLA Electrical Engineering Department and served on many thesis committees. Working with Frank Chen, he developed a theory of helicon discharges in nonuniform plasmas, with emphasis on the energy deposition from Trivelpiece-Gould modes. He preferred to solve problems analytically as far as possible before resorting to the computer. Together with Art Peskoff, he found an analytic solution to the propagation of helicon waves in a nonuniform magnetic field. To help with experiments, he devised a user-friendly code for the excitation, propagation, and absorption of helicon waves in bounded, nonuniform plasmas.

Because of his gentle, soft-spoken, and modest manner, Don's many scientific accomplishments are not well known, even to his friends and colleagues. However, they all remember his warm personal interactions with them. Students he has worked always remember how he used to come down to the lab helping them figure stuff out, always optimistic and enthusiastic about the projects, always seemingly in a good mood, with plenty of jokes. They can't remember a time when he didn't have something encouraging to say. His many friends around the world will feel his loss greatly. He was a highly kind and intelligent man, and an excellent physicist.