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We investigate the signals from neutral He atoms observed from Earth orbit in2010 by IBEX. The full He signal observed during the 2010 observation seasoncan be explained as a superposition of pristine neutral interstellar He gas andan additional population of neutral He that we call the Warm Breeze. The WarmBreeze is approximately two-fold slower and 2.5 times warmer than the primaryinterstellar He population, and its density in front of the heliosphere is ~7%that of the neutral interstellar helium. The inflow direction of the WarmBreeze differs by ~19deg from the inflow direction of interstellar gas. TheWarm Breeze seems a long-term feature of the heliospheric environment. It hasnot been detected earlier because it is strongly ionized inside theheliosphere, which brings it below the threshold of detection via pickup ionand heliospheric backscatter glow observations, as well as by the directsampling of GAS/Ulysses. Possible sources for the Warm Breeze include (1) thesecondary population of interstellar helium, created via charge exchange andperhaps elastic scattering of neutral interstellar He atoms on interstellar He+ions in the outer heliosheath, or (2) a gust of interstellar He originatingfrom a hypothetic wave train in the Local Interstellar Cloud. A secondarypopulation is expected from models, but the characteristics of the Warm Breezedo not fully conform to modeling results. If, nevertheless, this is theexplanation, IBEX-Lo observations of the Warm Breeze provide key insights intothe physical state of plasma in the outer heliosheath. If the second hypothesisis true, the source is likely to be located within a few thousand of AU fromthe Sun, which is the propagation range of possible gusts of interstellarneutral helium with the Warm Breeze characteristics against dissipation viaelastic scattering in the Local Cloud.

Warm Breeze from the starboard bow: a new population of neutral helium in the heliosphere