Energetic helium atoms may be the key to understand the IBEX Ribbon Print E-mail
Monday, 03 March 2014 11:21

The discovery of the IBEX Ribbon, which is an area on the sky of enhanced emission of hydrogen atom flux, was a surprising finding of the Interstellar Boundary Explorer mission. The origin of the Ribbon is yet unknown and there are several competing hypotheses on Ribbon’s sources. According to one of them, the Ribbon forms in the Local Interstellar Cloud near the heliospheric boundary due to interaction of solar wind neutral particles with interstellar matter. According to another hypothesis, proposed by a team of researchers from CBK PAN led by Professor Stanisław Grzędzielski and published in 2010 in The Astrophysical Journal Letters, the Ribbon is a result of interaction between the Local Interstellar Cloud boundary and the Local Bubble. That happens much farther away from the Sun than in the first case. Those two totally different hypotheses explain the formation of similar energetic hydrogen atom fluxes, making it difficult to eliminate one of them on the basis of existing energetic hydrogen atoms measurements. To solve this dilemma, CBK PAN researchers have recently proposed to use observation of energetic helium atoms.

In an article published in Astronomy and Astrophysics, CBK PAN scientists suggested that the level of energetic helium atom fluxes, formed in the heliosphere itself, should be relatively low and the maximum of signal expected should focused on the sky in the region of the heliospheric tail. In another work, just published in The Astrophysical Journal by a CBK PAN PhD student-Paweł Swaczyna and collaborators, it was suggested that the Ribbon will be hard to distinguish from the heliospheric signal in helium fluxes, if its formed right at the boundary of the heliosphere. However, if Grzedzielski’s extraheliospheric hypothesis is true, the helium Ribbon should form the dominant structure in the sky.

Thus, in future neutral atom-astronomy missions, detectors of the energetic neutral helium atoms will hopefully allow to better understand the nearest surrounding of the heliosphere.

IBEX (Interstellar Boundary Explorer) is a NASA Small Explorer mission. Southwest Research Institute in San Antonio, TX, developed and leads the mission with a team of US and international partners. NASA's Goddard Space Flight Center in Greenbelt, MD., manages the Explorers Program for NASA's Science Mission Directorate in Washington, DC.

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