In Memoriam: Stanley D. Shawhan 1941 - 1990 A Tribute to Stanley D. Shawhan by Donald A. Gurnett Presented at the NASA "Space Physics Workshop for High School Science Teachers," University of Iowa, Iowa City, Iowa, July 10, 1992.

This workshop is dedicated to the memory of Stanley D. Shawhan who died a little over two years ago. Since many of you probably did not know Stan, I would like to briefly describe some of the important contributions he made to the field of space physics.

I first met Stan as a fellow graduate student when he arrived at the University of Iowa in the fall of 1963. This was an exciting time for space research at Iowa. Only a few months earlier, in December 1962, we had flown a very-low-frequency (VLF) radio receiver on a spacecraft called Injun III. This receiver, which was one of the first of its type to be flown on an Earth-orbiting spacecraft, was a great success. We all marveled at the astonishing variety of naturally occurring VLF radio phenomena detected as the spacecraft passed through the Earth's radiation belts and auroral zones. It was Prof. Van Allen, I believe, who first suggested that Stan work with me on the interpretation of these signals. At that time, I was particularly interested in a nearly constant frequency oscillation, at about 500 Hz, that often followed an impulsive signal called a whistler, which was known to be produced by lightning. As part of my Ph.D. research, I had developed a theory for the generation of this oscillation, now known as a proton whistler. Stan's role in the research was to carry out a large scale survey of the data to establish the basic facts concerning this phenomena. For example, we were soon able to show that the frequency of the oscillation was related to a characteristic frequency of protons in the Earth's magnetic field known as the proton cyclotron frequency, hence the term proton whistler. This research led to Stan's first space-related publication, which was entitled "Experimental Observations of Proton-Whistlers from the Injun 3 VLF Data." Together we were able to not only confirm the basic theory involved, but also to develop methods of using proton whistler signals as a diagnostic tool. In particular, by measuring a characteristic frequency known as the crossover frequency, it was possible to compute the fractional concentration of protons in the Earth's ionosphere. At the time, this was the best method of determining this important parameter, which gave information on the structure of the Earth's ionosphere.

From these modest beginnings the area now known as space plasma wave research developed and flourished at the University of Iowa. Stan Shawhan played a vital role in this early development by contributing important new ideas and carrying out the associated research. In 1966, under my direction, he completed a Ph.D. thesis, the title of which was "VLF Ray Tracing in a Model Ionosphere." The main point of this thesis was the development of a computer code for calculating the ray path of low frequency radio waves in the Earth's ionosphere and magnetosphere. This work has since become one of the primary references for researchers interested in studying the ray path of radio waves in planetary magnetospheres. Many of the ray tracing codes currently in use in this country can be directly linked to the code that he developed over twenty-five years ago. After completing his Ph.D. degree, Stan continued as a research scientist at the University of Iowa for a period of two years. His primary effort during this time was the development of two rocket payloads (Javelin 8:45 and 8:46) that were successfully launched from Wallops Island, Virginia, and Fort Churchill, Canada. He then moved to Sweden as a visiting scientist at the Royal Institute of Technology, where he worked for a period of about one year. In Sweden, Stan developed many close friends and colleagues, and established an international outlook toward scientific cooperation that would later be of great value.

In 1969 Stan returned to Iowa, where he had been offered and accepted a position as an Assistant Professor in the Department of Physics and Astronomy. This move marked the beginning of the second phase of his career, this time as an educator. Stan was a great success as a teacher. His intense interest in science, his enthusiasm, and his well-organized lectures were very popular among students. I was always very impressed with his ability to motivate students, and to transfer his enthusiasm to them. He enjoyed teaching so much that for a few years he even taught an elementary electronics course in his spare time for home hobbyists. During his early years as a professor, Stan gradually shifted his interests to radio astronomy, and he soon had a flock of devoted graduate students working with him on various projects. His most notable undertaking during this period was a large radio astronomy antenna that he constructed, with tremendous personal effort, in the desert near Borrego Springs, California. In the mid-1970s his interests again shifted back to space research. I always suspected that his wife, Sue, had something to do with this, since I don't think that she, and her two sons, Peter and Daniel, were very happy with summer vacations in the desert, where the temperature often reached 110øF. Stan soon won a large NASA contract to develop a spacecraft called the Plasma Diagnostics Package (PDP), which was subsequently flown twice on the space shuttle. The PDP project was very successful and provided a wealth of new data on the interaction of large moving objects with the ionosphere. Probably more important, it gave Stan valuable first-hand knowledge of the scientific and technical problems associated with the management of large spacecraft projects. It also played, I believe, an important role in stimulating his interest in scientific administration, which was to be the third, and probably most important phase of his career.

In 1983, Stan moved to NASA Headquarters in Washington, D.C. His move to NASA Headquarters came at a crucial time for space plasma physics. In the early 1980s the NASA Solar-Terrestrial Physics Division had been dismantled and the space physics program was in disarray. At the urging of the Space Science Board, it was eventually decided that a new division was to be formed, and Stan was selected as the head of the new division, now called the Space Physics Division. Stan tackled this new challenge with great energy and enthusiasm. He recognized that modern space science is truly international in scope, and requires the resources of many nations to carry out the broad range of measurements required to study global phenomena. Over a period of several years, after countless trips to foreign countries and many trials and tribulations, he succeeded in developing a large international program, through which coordinated measurements could be made by many nations. The U.S. contribution to this effort is called the International Solar Terrestrial Physics (ISTP) program. This program consists of a large fleet of spacecraft (in some cases involving spacecraft from other countries) that will be launched during this decade. Unfortunately, Stan died before this program came to fruition. The first ISTP spacecraft, called Geotail, will be launched later this month. Thanks to Stan's efforts we now have a vigorous program of solar-terrestrial research that will serve the scientific community for many years to come.

Stan Shawhan was an accomplished researcher, a gifted teacher, and an outstanding leader of the scientific community. He seemed to have boundless energy. He was always ready to listen to different points of view, and was very effective at formulating solutions to complex problems. Above all, he was able to motivate people. If he were here today, I am certain that he would be pleased that so many distinguished scientists and educators have come to this workshop to study and about the subject that he loved so much.