Mystery of the Ribbon, Solved?

CSPAR and Department of Physics Professors Jacob Heerikhuisen, Nick Pogorelov, and Gary Zank were in the news recently. All three had been part of the successful NASA IBEX spacecraft team that had, much to everyone’s considerable surprise last year discovered a giant ribbon  of energetic neutral atom emission at the edge of the solar system, leaving researchers mystified. To quote several news articles, the researchers called it a “shocking result” and puzzled over its origin. Now the mystery may have been solved . In an Astrophysical Journal Letter that appeared on 10 January 2010, Heerikhuisen, Pogorelov, and Zank introduced a new physical process not considered before, and were able to emerge with a compelling explanation only two months after the observation had first been reported. The Figure below shows the correspondence between the observed ribbon feature and that simulated by UAH researchers.

The impact of our simulations has been dramatic (multiple NASA press releases and related news stories), but more importantly presents a concrete demonstration of discovery and explanation through computational modeling in concert with very sophisticated observations. Not only has our approach proved transformational to the space physics community in understanding and modeling complex systems, but it is introducing a new paradigm for space missions by including state-of-the-art simulation and modeling as part of the mission itself. In the same sense that we employ software on an MRI scan to transform the data into a 3D image of the patient for a doctor, the observations returned by IBEX can be understood only by applying state-of-the-art computer simulations to the data to extract knowledge of the physics behind the system.

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These two maps show the entire sky in the emission of neutral hydrogen. The energetic neutral atom (ENA) measurements by the IBEX mission (top image) show a ribbon feature spanning the entire sky. With our models, we discovered that this feature can be understood and reproduced (bottom image) after adding an unpredicted "mirror effect". The two images show observed and modeled ENAs, respectively, at comparable speeds [Heerikhuisen et al., 2010]