March 10, 2014
Van Allen Probes Helping To Refine Space Weather Computer Models
redOrbit Staff & Wire Reports - Your Universe Online
Data from the Van Allen Probes has been combined with a high-powered computer model to help researchers test and improve the forecast model to determine how the two giant near-Earth radiation belts they orbit can affect technology in space, NASA officials reported on Friday.The Van Allen radiation belts, which are teeming with rapidly-moving particles and a space weather system that varies in response to incoming solar particles and energy, can be influenced by various events that cause them to swell. As a result, electrons accelerate to 99 percent of the speed of light and impact nearby satellites – something scientists hope to be able to predict by understanding the root causes of these phenomena.
Scientists affiliated with the US space agency have taken information from the probes and used that data to improve the Dynamic Radiation Environment Assimilation Model in 3 Dimensions (DREAM3D), a computer simulation created by the Los Alamos National Laboratory (LANL) in New Mexico. The result is a pair of new studies, both of which appear in the journal Geophysical Research Letters and provide a robust new method to simulate the events that take place in the Van Allen belts.
“The Van Allen Probes are gathering great measurements, but they can't tell you what is happening everywhere at the same time,” LANL scientist Geoff Reeves, a co-author on both of those studies, explained in a statement. “We need models to provide a context, to describe the whole system, based on the Van Allen Probe observations.”
When the Van Allen Probes launched in August 2012, they became the only operational spacecraft constructed to compile information on the radiation belts in real-time. However, while they represent a significant advancement in the field of space weather data collection, they are unable to monitor data in all corners of the radiation belts at the same time. Fortunately, scientists now have enough data available to build computer models to help out.
One of the two new studies, which was published on February 7, “provides a technique for gathering real-time global measurements of chorus waves, which are crucial in providing energy to electrons in the radiation belts,” officials at the space agency explained.
In this study, the authors combined information about chorus wave behavior in the belts that was collected by the Van Allen Probes with that obtained using the NOAA’s low altitude Polar-orbiting Operational Environmental Satellites (POES). They then took all of that information, along with some additional historical data, and correlated the low-energy electrons falling out of the belts with what was actually occurring directly inside of the region.
“Once we established the relationship between the chorus waves and the precipitating electrons, we can use the POES satellite constellation – which has quite a few satellites orbiting Earth and get really good coverage of the electrons coming out of the belts,” said Yue Chen, an LANL scientist and first author of the study. “Combining that data with a few wave measurements from a single satellite, we can remotely sense what's happening with the chorus waves throughout the whole belt.”
In the second study, the authors detailed how they used data from the chorus wave technique, the Van Allen Probes and NASA's Advanced Composition Explorer (ACE) – which measures solar wind particles – in order to strengthen the DREAM3D computer model. They then compared those simulations, which could for the first time incorporate real-time information, to an actual solar storm that had taken place in October 2012.
Lead author Weichao Tu, also of Los Alamos, called the storm “remarkable and dynamic” and said there were two periods of peak activity during its course – one in which the fast electrons were completely wiped out, and one in which there number of high-energy, accelerated electrons increased one thousand times in a matter of hours.
She and her colleagues ran the augmented DREAM3D model, which incorporated the additional information, and found that they were able to recreate a storm extremely similar to that October 2012 event. Their research also helped to explain the different impact produced by each of the two peaks.
“During the first peak, there simply were fewer electrons around to be accelerated. However, during the early parts of the storm the solar wind funneled electrons into the belts. So, during the second peak, there were more electrons to accelerate,” NASA explained.
The researchers report that these findings have given them confidence in the enhanced model, as well as hope that they are beginning to gain new insight into the Van Allen belts themselves.