James Alfred Van Allen
Van Allen, James Alfred (1914-) is an American physicist who discovered the Van Allen belts, two zones of electrically charged particles that surround the earth. The belts were named for him. His team of scientists used data from the United States Explorer 1 satellite to make the discovery in 1958. Van Allen took part in many other high-altitude research and rocket development projects.
Van Allen was born Sept. 7, 1914, in Mount Pleasant, Iowa. He was the second of four sons of Alfred M. Van Allen, an attorney, and Alma (Olney) Van Allen, a former teacher in a oneroom schoolhouse. The family valued education and allowed the boys to spend time pursuing scientific and mechanical interests. Van Allen conducted experiments, read Popular Mechanics magazine, and built a generator with one brother. By the time he entered high school, Van Allen had become passionate about physics.
Van Allen graduated from Iowa Wesleyan College in 1935. He then earned a master's degree in 1936 and a doctorate in 1939, both from the University of Iowa (UI). Van Allen then worked at the Carnegie Institution in Washington, D.C., as a research fellow. In 1942, he took a position at the Applied Physics laboratory at Johns Hopkins University, where he developed a vacuum tube.
Later that year, Van Allen joined the U.S. Navy, serving as an ordnance and gunnery specialist and combat observer during World War II (1939–1945). During the war years, he developed special fuses for use with anti-aircraft weapons used by the Navy. These radio proximity fuses were tracking devices attached to missiles. A missile is a self-propelled bomb or rocket. The devices guided explosive weapons to the target and then detonated. More accurate hits could be made with these fuses. Van Allen worked in the field in the South Pacific testing his fuses.
From his experience in the Navy, Van Allen became skilled in miniaturizing instruments. After the war, American military personnel captured advanced rockets called V-2 missiles from the Germans. Van Allen oversaw a program to research these rockets at the White Sands Proving Ground, established in New Mexico in 1945. The United States tested its first missiles there in 1945, shortly before the end of World War II. (The Army renamed the site White Sands Missile Range in 1958. The first atomic bomb was exploded in July 1945 at Trinity Site, on the eastern side of the range.)
The researchers tried to duplicate the V-2 missiles, but were not able to. However, they made a version that was similar, though not as powerful. It was called the Aerobee, and was designed strictly for scientific purposes. From 1946 to 1951, scientists launched more than 60 V-2's and Aerobees that carried scientific instruments into high altitudes for research. The scientists sought information about the upper atmosphere, including cosmic rays.
In 1951, Van Allen returned to the University of Iowa. He became professor of physics and head of the UI department of physics and astronomy, where he remained until 1985. He soon began using his rocket expertise to create instruments to explore the atmosphere. Scientists had been using balloons to collect information from the sky for some time. Balloon explorations of the upper atmosphere reached new heights in the early 1930's when Swiss physicist Auguste Piccard ascended in huge hydrogen-filled balloons into the stratosphere, the atmospheric layer about 10 to 30 miles (16 to 48 kilometers) above the earth, above nearly all clouds to study cosmic rays, high-energy particles that originate in outer space.
Van Allen combined his knowledge of rockets with balloon technology to create what he called a “rockoon,” a balloon carrying a rocket. After the balloon reached its highest possible height, the rocket would go off, reaching much further heights. This method enabled Van Allen to collect valuable new information about Earth's atmosphere.
In 1955, both the Soviet Union and the United States announced their intention to launch artificial earth satellites. The Soviet Union sent off Sputnik, the first artificial satellite to orbit the earth, on October 4, followed by Sputnik 2 on November 3. The Americans created the Vanguard satellite, but it went up in flames in a launch failure in December. The United States launched a spacecraft named Explorer 1 on Jan. 31, 1958. It was designed and built by a group of scientists from the University of Iowa led by Van Allen. Van Allen equipped the spacecraft with a Geiger counter, a device for detecting ionizing radiation. His goal was to measure the intensity of cosmic rays. Van Allen wanted to learn about the low end of the cosmic ray energy range.
The orbit of Explorer 1, being elliptical, ranged from 219 to 1,575 miles (352 to 2,535 kilometers) from the earth. The data that came back were puzzling. At low points of the orbit, the number of particles fit Van Allen's expectations. But at the high end of the orbit, no particles were detected at all. Explorer 4, carrying more elaborate scientific instruments, confirmed that finding, as did later spacecraft.
Based on these data, Van Allen figured out the existence of the radiation belts. The Van Allen belts are two zones of electrically charged particles that surround the earth high above its surface. The belts surround the earth somewhat like doughnuts. The inner belt extends from about 600 to 3,000 miles (1,000 to 5,000 kilometers) above the earth. The outer belt reaches from about 9,300 to 15,500 miles (15,000 to 25,000 kilometers). The radiation in the belts consists of high concentrations of charged particles, such as protons and electrons. The earth's magnetic field traps such particles and directs them toward the magnetic poles. The earth's magnetic field includes the space around the planet in which its magnetism can be observed, and extends far out beyond the atmosphere. The trapped particles spiral along a system of imaginary lines of the magnetic field. These field lines curve from the north magnetic pole to the south magnetic pole. As particles approach either pole, the converging field lines reflect them back toward the opposite pole. This effect keeps particles in the belts bouncing between the poles.
The inner belt traps particles set free from the earth's atmosphere by cosmic rays, high-energy particles from outer space. The outer belt acquires particles from the solar wind, a continuous stream of charged particles from the sun, and from solar flares, violent eruptions on the sun's surface. Intense solar activity disrupts the belts and leads to magnetic storms. Disruptions of the belts also interfere with radio reception, cause surges in power transmission lines, and produce auroras (streamers or bands of light appearing in the sky at night). Like Earth, Jupiter, Saturn, Uranus, and Neptune are surrounded by magnetic fields. In the 1970's and 1980's, the Voyager space probes found evidence that these planets also have radiation belts.
Van Allen's discovery made him a national hero at a time when the United States was competing against the Soviet Union to win the space race. Time magazine featured him on its cover.
After he retired from UI's department of physics and astronomy in 1985, Van Allen became a professor emeritus. In his late 80's, he still worked nearly 40 hours a week in an office in a building named for him.
Van Allen held memberships in numerous science societies, including the American Rocket Society, the Institute of Electrical and Electronics Engineers, and American Physics Society. He was a founding member of the International Academy of Astronautics and served as a consultant to, and member of, several government committees. He won many prestigious awards from science organizations.