Iowa Academy of Science The New Bulletin Volume 2 Number 4 Autumn 2006

James A. Van Allen, a native of Iowa, and the world renowned space scientist who discovered Earth's radiation belts, died in Iowa City, Iowa, on August 9, 2006.

Born in the small town of Mt. Pleasant on September 7, 1914, he received a Bachelor of Science degree from Iowa Wesleyan College in 1935, and a Ph.D. degree in Physics from the University of Iowa in 1939. He then moved to the Carnegie Institute in Washington D.C., where he planned to do research on cosmic rays. However, before he could make much progress, World War II intervened, and his work was shifted to the development of radio-proximity fuses for antiaircraft shells. In 1942 the proximity fuse project was moved to the Johns Hopkins Applied Physics Laboratory. When the development phase was completed, he was commissioned as a lieutenant in the U.S. Navy and sent into the Pacific to test the shells under combat conditions. For this service he received four combat stars.

After the war, he returned to Johns Hopkins where he rekindled his interests in cosmic rays and pioneered the development of Geiger tube instrumentation for flight on captured German V-2 rockets. These flights resulted in the first measurements of cosmic rays at high altitudes above Earth's atmosphere, as well as other measurements of atmospheric ozone, solar ultra-violet light, and the geomagnetic field. He also supervised the development of a smaller U.S. rocket, called the Aerobee, that had capabilities similar to the V-2s.

In 1951 he moved back to Iowa to accept a position as Professor and Head of the Department of Physics at the University of Iowa. There he developed a low-cost balloon-borne rocket, called a rockoon, that could reach altitudes comparable to those achieved by the V-2 and Aerobee rockets. This work led to the first latitudinal survey of the cosmic ray intensity above Earth's atmosphere using a series of rockets launched from ships as part of the International Geophysical Year, 1957-58. During this same period he started studying the feasibility of launching an artificial satellite, and was funded to develop a Geiger-tube cosmic ray detector for the Vanguard program, which was designed to launch a spacecraft into a low Earth orbit. However, before these plans came to fruition, the Soviet Union launched Sputnik 1, the world's first satellite. In the resulting frantic effort to catch up with the Soviet Union, Van Allen was asked to install his instrumentation on a spacecraft to be launched by a rocket under development by Werner von Braun at the U.S. Army's Redstone Arsenal. The spacecraft, Explorer 1, was successfully launched on February 1, 1958. Expecting to see a relatively steady cosmic ray counting rate, Van Allen and his colleagues were surprised to obtain data from some ground receiving stations in which there were no counts at all. Not wanting to believe that the instrument had failed, he postulated that the satellite was flying through regions with exceedingly high radiation intensities, so high that they saturated the Geiger tube, rendering it inoperative. After a launch failure with Explorer 2, a similar instrument was launched on Explorer 3, which carried a tape recorder that allowed data to be obtained for an entire orbit. These data confirmed the saturation hypothesis and showed that Earth is encircled by two very intense donut-shaped belts of energetic charged particle radiation, now known as the Van Allen radiation belts.

The totally unexpected discovery of very intense and highly energetic belts of radiation encircling Earth immediately attracted worldwide attention. Van Allen and his colleagues soon showed that the radiation belt particles were trapped in stable, long-lived orbits by Earth's magnetic field. In the next few years, this area of space research expanded rapidly and developed into the field now known as magnetospheric physics. Over the course of his career Van Allen provided similar energetic charged particle detectors for twenty spacecraft projects, including the first flights to the planets Venus, Mars, Jupiter and Saturn. Although Venus and Mars proved to have no internally generated magnetic fields, and no radiation belts, with the Pioneer 10 and 11 spacecraft he was the first to show that Jupiter and Saturn had intense radiation belts and large extended magnetospheres. Even after retirement in 1985 he remained active in his research. As the Pioneer 10 and 11 spacecraft proceeded outward toward interstellar space after their encounters with Jupiter and Saturn, he made the first measurements of the radial variation in the cosmic ray intensity with the distance from the Sun. These measurements provided a crucial insight into the entry of cosmic rays into the solar system, a topic that he continued to study up to the time of his death at age 91.

From his earliest days at the University of Iowa, Van Allen made a practice of involving students in his research, thereby contributing to the education of an entire generation of space scientists, many of whom went on to be leaders in space research at government, industry and university institutions. He was also a very popular lecturer, and for seventeen years before his retirement taught a large undergraduate course in astronomy. Even today, more than twenty years after he last taught this course, it is not uncommon to run across people from all walks of life who say that one of their most memorable experiences at the University of Iowa was taking ''Van Allen's Astronomy Course.'' For his research and teaching he received many awards, including memberships in the Iowa Academy of Science and the National Academy of Sciences, the National Medal of Science from President Ronald Reagan in 1987, and the Crafoord Prize from the King of Sweden in 1989, just to mention a few. He was not only a gifted researcher and educator, but was also a very kind caring person who loved to help people. He will be greatly missed by all who knew and worked with him.