Lunar orbiters discover source of space weather near Earth
"The amount of power converted was comparable to the electric power generation from all power plants on Earth — and it went on for over 30 minutes," said Vassilis Angelopoulos, a professor in the UCLA Department of Earth, Planetary and Space Sciences, principal investigator for ARTEMIS and THEMIS, and lead author of the research in Science. "The amount of energy released was equivalent to a 7.1 Richter-scale earthquake."
(Space weather process: Solar storm eruption influences Earth's magnetic field, resulting in explosive burst of energy known as magnetic reconnection.)
Trying to understand how gigantic explosions on the sun can have effects near Earth involves tracking energy from the original solar event all the way to Earth. It is like keeping tabs on a character in a play who undergoes many costume changes, researchers say, because the energy changes frequently along its journey: Magnetic energy causes solar eruptions that lead to flow energy as particles hurtle away, or to thermal energy as the particles heat up.
Near Earth, that energy can go through all the various changes in form once again. Understanding the details of each step in the process is crucial for scientists to achieve their goal of someday predicting the onset and intensity of space weather.
Using ARTEMIS, a clear picture emerged of the total energy stored, and the entire fleet of satellites tracked the energy fronts at high time resolution, Angelopoulos said.
The spacecraft and satellites observed two expanding energy fronts launched symmetrically on either side of the magnetic reconnection site, one moving toward Earth and the other away from it, past the moon. The magnetic energy was transformed into particle and wave energy during its quarter-million–mile journey from its origin within a narrow region only a few dozen miles across.
This, the researchers said, explains why single-satellite measurements in the past did not make much of the energy release. The multiple satellite fleet, however, showed that the energy conversion continued for up to 30 minutes after the onset of reconnection.
"We have finally found what powers Earth's aurora and radiation belts," Angelopoulos said. "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."
With the full, global picture of energy storage and transfer in the magnetosphere, scientists can now focus their attention on the physics of the energy conversion and its eventual dissipation in order to improve space weather forecasts.
What scientists learn on Earth can also inform our knowledge elsewhere in our solar system. The sun's eruptions are also controlled largely by magnetic reconnection, and intense auroras at Jupiter create the most powerful electromagnetic emissions in the solar system besides the sun, Angelopoulos said.
Similar emissions from planets orbiting other stars may one day reveal the interior structure of distant worlds. Since the sun's surface and very distant planets cannot yet be visited, there is no place better than Earth's own space environment to study energy transformation on large and small scales with a coordinated fleet of highly capable satellites, he said.
NASA is currently building the Heliophysics System Observatory, which combines existing and future satellite resources in space, including THEMIS, ARTEMIS, the recently launched twin Van Allen Radiation Belt Probes, and the four Magnetospheric MultiScale satellites, which will be launched in 2014 (and which have involved UCLA scientific and hardware participation).
"It is a very exciting time ahead," said David Sibeck, THEMIS/ARTEMIS project scientist at NASA's Goddard Space Flight Center. "Never before did we have the possibility for so many high-quality observatories lining up."
ARTEMIS stands for Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun. THEMIS (Time History of Events and Macroscale Interactions during Substorms) was launched Feb. 17, 2007, from Cape Canaveral, Fla., to impartially resolve the trigger mechanism of substorms. Themis was the blindfolded Greek goddess of order and justice.
THEMIS and ARTEMIS are part of NASA's Explorer program, managed by the Goddard Space Flight Center. UC Berkeley's Space Sciences Laboratory is responsible for mission operations and built several of the on-board and ground-based instruments. Austria, Canada, France and Germany contributed instrumentation, operations and science. ATK (formerly Swales Aerospace), built the THEMIS spacecraft. ARTEMIS's orbit design, navigation and execution were the result of a collaborative effort among NASA's Jet Propulsion Laboratory, the Goddard Space Flight Center and UC Berkeley. UCLA scientists built the ground magnetometers.
Legal Disclaimer:
EIN Presswire provides this news content "as is" without warranty of any kind. We do not accept any responsibility or liability for the accuracy, content, images, videos, licenses, completeness, legality, or reliability of the information contained in this article. If you have any complaints or copyright issues related to this article, kindly contact the author above.
