Experimenting with the Van Allen Belts

Ever since the Van Allen radiation belts were discovered, the U.S. armed forces have been interested in understanding—and maybe even controlling—how the belts influence wireless communication. For example, the U.S. Air Force, wanting to keep in touch with airborne fighter pilots at all times, would like to understand exactly how geomagnetic storms in the atmosphere will cause disruptions. Today, the armed forces are sponsoring two big experiments to gain more knowledge about the Earth's ionosphere. The first of them is the High Frequency Active Auroral Research Program (HAARP), located in Gakona, Alaska, about 300 kilometers from Fairbanks.
Built on an old Cold War site meant to house an over-the-horizon radar, HAARP's main job is to produce radio waves to probe the ionosphere. Gakona is a particularly interesting location for HAARP, because “the Earth's magnetic field lines come down to Earth there,” says Paul Kossey, HAARP's program manager for the Air Force Research Laboratory. One of the chief instruments at HAARP is a multimegawatt radio transmitter operating in the high-frequency (HF) range, known as the Ionospheric Research Instrument, which reached full power only last March. The idea is to beam radio signals into the ionosphere and thereby stimulate or heat small, well-defined volumes of ionosphere. Back on the ground, an array of geophysical research instruments—such as low-frequency receivers, magnetometers, an ultrahigh-frequency (UHF) diagnostic radar, optical, and infrared spectrometers and cameras—try to see what happens to the ionosphere as a result of these signals. “A lot of things we are doing are to mimic natural processes in a controlled fashion,” says Kossey. He says that the transmitter would be able to radiate about 3 to 4 megawatts—“about three times the power of Radio Moscow or Voice of America.” In the future, HAARP scientists hope to complete a UHF radar to allow measurement of electron and ion temperatures and electron densities, which are important to understanding the origins of satellite-damaging so-called killer electrons. The other Air Force Research Lab ionosphere experiment is a spacecraft called the Demonstration and Science Experiments (DSX) satellite, which is set to launch in 2009. DSX is designed primarily to investigate the sometimes harsh radiation that environment satellites are subject to in a medium Earth orbit. The satellite will also have an instrument designed to monitor very-low-frequency (VLF) transmissions in the magnetosphere—the magnetic shell surrounding the Earth—and will explore whether natural and man-made VLF waves, including those from HAARP, can reduce satellite-damaging space radiation. Several years ago, Stanford University electrical engineering professor Umran S. Inan theorized that low-frequency electromagnetic radiation injected into the lower Van Allen belt could cause the high-energy electrons there to prematurely rain out into the atmosphere, potentially ending a monthlong geomagnetic storm in a matter of days.