September 1, 2013
Several Key Discoveries During Van Allen Probes First Year
redOrbit Staff & Wire Reports – Your Universe Online
NASA’s twin Van Allen Probes entered their second year of service Friday having already provided a wealth of new information about the layers of energetic charged particles located above our planet.
According to the US space agency, data collected by the probes since their August 30, 2012 launch has already led to “several significant discoveries” about the Van Allen radiation belts -- some of which came within the first few days of the two robotic spacecraft’s mission. Thus far, the probes have answered one long-standing question about the nature and behavior of the belts, and also revealed that the outer belt can be split into two separate ones.
“The science results are coming fast now,” NASA’s Mona Kessel, program scientist for the satellites formerly known as the Radiation Belt Storm Probes, explained in a statement. “Some of the discoveries we’ve made are going to rewrite the textbooks on the radiation belts. And while those discoveries are fascinating and merit more research, we’re still focused on the question we asked when we designed the mission: What are the primary mechanisms of particle loss and acceleration in the belts? We’re beginning to answer that now.”
The Van Allen radiation belts are a pair of donut-shaped regions of highly energetic particles trapped within the planet’s magnetic field. The inner belt is located just above the atmosphere and extends some 4,000 miles into space, NASA said, while the outer belt extends from 8,000 to 26,000 miles out. They (and the twin probes studying them) are named in honor of the late James A. Van Allen, a University of Iowa scientist who was instrumental in establishing the field of magnetospheric research in space.
Shortly after the Van Allen Probes launched, scientists turned on the Relativistic Electron Proton Telescope (REPT) instrument and discovered a third radiation belt, formed at the interior of the outer belt. That belt, which was said to be the result of a powerful electron acceleration event, would be destroyed just four weeks later by a solar storm -- which itself was an event that could not have been observed prior to the start of their mission.
“Just a few days later, on Sept. 5, members of the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) team made an audio recording of radio waves in the belts, at a frequency audible to humans, known as ‘chorus,’” NASA officials explained. “While scientists have known about chorus since the 1950s, these new high-quality recordings became known as ‘the sounds of space’ and drew a great deal of interest around the world. Chorus is caused by plasma waves in the belts, and is suspected to be related to the process that accelerates electrons to speeds which can harm spacecraft and astronauts.”
Moving forward, scientists involved with the mission hope the probes will be able to determine how the particles in the radiation belts are being accelerated to nearly relativistic speeds -- whether it is happening within the belts, or whether an external force plays a role in the phenomenon.
According to Geoff Reeves, a radiation belt scientist at Los Alamos National Laboratory and first author on a research paper discussing the topic, the agency has “real evidence that the changes originate from within the belts themselves.”
In addition, the probes’ Relativistic Proton Spectrometer (RPS) instrument has been able to record previously unavailable high-accuracy measurements of particles in the center of the inner radiation belts. Its findings have helped scientists learn more about spatial gradients (the physical distribution of energetic particles) in the inner belt, while also examining how protons from outside the solar system gain entry to the Earth’s magnetosphere, NASA explained. The RPS is also expected to influence the development of the next generation of standards and models used by the satellite community for building and shielding their spacecraft.
Scientists involved in the Van Allen Probe mission are excited about what lies ahead for the project.
“We are going to see a lot of different opportunities in the coming year for even more great science,” said Barry Mauk, Van Allen Probes project scientist at NASA’s Applied Physics Laboratory. “Because we’re going to be operating on the dusk-to-dawn side of Earth, we’re going to see different physical processes, and combined with the period we are in with solar max, we’re hopeful for a lot of interesting events.”
“Every week I learn something new,” Kessel added. “We are now going into what historically has been the most energetic part of the solar cycle for the radiation belts. So we might see brand new things this year, and we are in an excellent position to be ready for what the sun throws at us.”