Artist’s concept of the heliosphere, showing the relationship between the Voyager spacecraft (outside the Termination Shock, faint blue shell) and the Cassini spacecraft at Saturn. The blow-up of the Saturn system shows the Cassini spacecraft, which carries the Magnetospheric Imaging Instrument (MIMI) Ion and Neutral Camera (INCA). INCA produced heliospheric images in energetic neutral atom emission from Saturn at 10 astronomical units (AU) from the sun, still deep inside the heliosphere. The Earth is at 1 AU, and the Voyagers are now beyond 100 AU. Together, the Voyagers measure the energetic particles at two discrete locations in this vast system, while Cassini/INCA provides global images of the system (from the inside). Credit: (Credit: NASA and JHU/APL)

New ‘Retention Model’ Explains Enigmatic Ribbon at Edge of Solar System

Feb. 5, 2013 — Since its October 2008 launch, NASA’s Interstellar Boundary Explorer (IBEX) has provided images of the invisible interactions between our home in the galaxy and interstellar space. Particles emanating from this boundary produce a striking, narrow ribbon, which had yet to be explained despite more than a dozen possible theories. In a new “retention model,” researchers from the University of New Hampshire and Southwest Research Institute suggest that charged particles trapped in this region create the ribbon as they escape as neutral atoms.

The Sun continually sends out a solar wind of charged particles or ions traveling in all directions at supersonic speeds. IBEX cameras measure energetic neutral atoms (ENAs) that form when charged particles become neutralized.

As solar wind ENAs leave the solar system, the majority move out in various directions, never to re-enter. However, some ENAs leave the solar system and impact other neutral atoms, becoming charges particles again. These newly formed pickup ions begin to gyrate around the local interstellar magnetic field just outside the solar system. In the regions where the magnetic field is perpendicular to their initial motion, they scatter rapidly and pile up. From those regions, some of those particles return to the solar system as secondary ENAs — ENAs that leave the solar system and become charged and then re-neutralized, only to travel back into the solar system as ENAs a second time.

Read more: New 'retention model' explains enigmatic ribbon at edge of solar system — Science Daily.

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