The Interstellar Boundary Explorer (IBEX): Tracing the Interaction between the Heliosphere and Surrounding Interstellar Material with Energetic Neutral Atoms

摘要

The Interstellar Boundary Explorer (IBEX) mission is exploring the frontiersof the heliosphere where energetic neutral atoms (ENAs) are formed from chargeexchange between interstellar neutral hydrogen atoms and solar wind ions andpickup ions. The geography of this frontier is dominated by an unexpectednearly complete arc of ENA emission, now known as the IBEX 'Ribbon'. Whilethere is no consensus agreement on the Ribbon formation mechanism, it seemscertain this feature is seen for sightlines that are perpendicular to theinterstellar magnetic field as it drapes over the heliosphere. At the lowestenergies, IBEX also measures the flow of interstellar H, He, and O atomsthrough the inner heliosphere. The asymmetric oxygen profile suggests that asecondary flow of oxygen is present, such as would be expected if some fractionof oxygen is lost through charge exchange in the heliosheath regions. Thedetailed spectra characterized by the ENAs provide time-tagged samples of theenergy distributions of the underlying ion distributions, and provide a wealthof information about the outer heliosphere regions, and beyond.