September 27, 2013
Multi-Satellite Observations Help Uncover Origins Of Space Weather
[ Watch the Video: What Really Causes Space Weather? ]
redOrbit Staff & Wire Reports - Your Universe Online
Space weather is caused by solar storms – powerful eruptions of solar material and magnetic fields into interplanetary space – and can interfere with wireless communication and GPS signals, cause extensive power blackouts, and even result in the complete failure of essential satellites.
Little had been known about the exact processes that caused these changing environmental conditions. However, in the new study, researchers from UCLA, NASA, the Austrian Space Research Institute (IWF Graz) and the Japan Aerospace Exploration Agency (JAXA) have helped to provide new insight into the phenomenon.
Some of the energy given off by the sun during solar storms becomes temporarily stored in Earth’s stretched, compressed magnetic field, the study authors explain. That solar energy is ultimately released in explosive fashion, powering the planet’s radiation belts and causing brilliant auroras to occur in the polar skies.
While experts have been able to observe solar storms using cameras, the process through which the stored magnetic energy is unleashed had previously gone unobserved. Now, however, the research team has managed to measure the release of that energy thanks to six Earth-orbiting spacecraft and NASA’s ARTEMIS dual lunar orbiters.
[ Watch the Video: Magnetospheric Substorm ]
“Space weather begins to develop inside Earth's magnetosphere, the giant magnetic bubble that shields the planet from the supersonic flow of magnetized gas emitted by the sun,” UCLA explained Thursday in a press statement. “During solar storms, some solar energy enters the magnetosphere, stretching the bubble out into a long, teardrop-shaped tail that extends more than a million miles into space.”
The stored magnetic energy is then released through a process known as “magnetic reconnection” – an event which can only be detected when energized particles speed past a spacecraft fortuitously positioned at the right place at the right time. Such an instance occurred in 2008, when NASA's five Earth-orbiting THEMIS satellites discovered that magnetic reconnection was the trigger for near-Earth substorms (the building blocks of space weather).
“However, there was still a piece of the space weather puzzle missing: There did not appear to be enough energy in the reconnection flows to account for the total amount of energy released for typical substorms,” the Los Angeles-based university said. “In 2011, in an attempt to survey a wider area of the Earth's magnetosphere, the THEMIS team repositioned two of its five spacecraft into lunar orbits, creating a new mission dubbed ARTEMIS.”
“From afar, these two spacecraft provided a unique global perspective of energy storage and release near Earth,” they added. “Similar to a pebble creating expanding ripples in a pond, magnetic reconnection generates expanding fronts of electricity, converting the stored magnetic energy into particle energy. Previous spacecraft observations could detect these energy-converting reconnection fronts for a split second as the fronts went by, but they could not assess the fronts' global effects because data were collected at only a single point.”
[ Watch the Video: Tracking Energy through Space ]
However, by last summer, the THEMIS and ARTEMIS satellites, JAXA’s Geotail satellite and the US National Oceanic and Atmospheric Administration (NOAA) GOES probe were in the proper alignment and managed to collect data accounting for the total amount of energy which leads to near-Earth space weather. According to the study authors, energy equivalent to a 7.1 Richter-scale earthquake was released during the event.
The vehicles and satellites observed as a pair of expanding energy fronts launched symmetrically on either side of the site where magnetic reconnection occurs. One moved towards Earth, while the other moved away from it and past the moon. The magnetic energy was converted into particle and wave energy during its 250,000 mile journey from its origin to a narrow region located just a few dozen miles across.
According to the study authors, this occurrence explains why single-satellite measurements in the past were unable to make much of the energy release. Conversely, the multi-satellite fleet was able to illustrate that the energy conversion process continued for as much as 30 minutes after the reconnection process started.
“We have finally found what powers Earth's aurora and radiation belts,” explained Vassilis Angelopoulos, a professor in the UCLA Department of Earth, Planetary and Space Sciences, principal investigator for the ARTEMIS and THEMIS missions, and lead author of the study. “It took many years of mission planning and patience to capture this phenomenon on multiple satellites, but it has certainly paid off. We were able to track the total energy and see where and when it is converted into different kinds of energy.”