In a paper published Feb. 4, 2013, in the Astrophysical Journal, researchers, including lead author Nathan Schwadron of the University of New Hampshire, propose a "retention theory" that for the first time explains all the key observations of this astrophysical enigma.
A three-dimensional diagram of the retention region shown as a "life preserver" around our heliosphere bubble along with the original IBEX ribbon image. The interstellar magnetic field lines are shown running from upper left to lower right around the heliosphere, and the area where the field lines "squeeze" the heliosphere corresponds to the ribbon location. The red arrow at the front shows the direction of travel of our solar system. Image credit: Adler Planetarium/IBEX Team.
"If the theory is correct," Schwadron notes, "the ribbon can be used to tell us how we're moving through the magnetic fields of the interstellar medium and how those magnetic fields then influence our space environment."
In particular, these strong magnetic fields appear to play a critical role in shaping our heliosphere - the huge bubble that surrounds our solar system and shields us from much of harmful galactic cosmic radiation that fills the galaxy. This may have important ramifications for the history and future of radiation in space, and its impact here on Earth, as the heliosphere changes in response to changing conditions in the interstellar medium or the "space between the stars."
Indeed, since the discovery of the ribbon, more than a dozen competing theories seeking to explain the phenomenon have been put forth. The retention theory "checks all the boxes, agrees with all the available observations, and the mathematical modeling results look remarkably like what the ribbon actually looks like," notes Schwadron. "This substantially raises the bar for models that attempt to explain the ribbon."
IBEX was launched in October 2008 and has provided images of the invisible interactions between the solar wind and the local galactic medium. The ribbon was captured using ultra-high sensitive cameras - one of which has components designed and built at the UNH Space Science Center - that image energetic neutral atoms (instead of photons of light) to create maps of the boundary region between our solar system and the rest of our galaxy.
Although the retention theory may check all the boxes, the IBEX team is still far from claiming that the ribbon is fully explained. A major test for the retention theory will be watching how the ribbon changes in step with observed changes in the solar wind. Notes Schwadron, "If what we observe matches what the model predicts should happen to the ribbon as the solar wind changes, that will go a long way toward validating the model."
IBEX is the latest in NASA's series of low-cost, rapidly developed Small Explorer space missions. Southwest Research Institute in San Antonio, Texas, leads the IBEX mission with teams of national and international partners. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the Explorers Program for NASA's Science Mission Directorate in Washington, D.C.
David Sims | EurekAlert!
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