Updated modeling of interstellar and secondary neutral helium in the heliosphere

Abstract:

An accurate heliospheric neutral test-particle code for primary helium atoms from the interstellar medium (ISM), and for secondary helium atoms born in the outer heliosphere (specifically, in the outer heliosheath ahead of the heliopause), is coupled to global heliospheric models dominated by hydrogen and protons from the solar wind and the ISM. This coupling enables forward modeling estimates of charge exchange losses of primary helium and production and losses of secondary helium as they travel from remote regions to the inner heliosphere. Taking additionally photoionization into account, a detailed characterization of neutral helium distributions and fluxes in the inner heliosphere is obtained and presented, with an eye toward supporting the analysis of data by Ulysses, IBEX, and IMAP. Preliminary findings of the effects of a solar cycle time-dependent global heliosphere and time-dependent photoionization rates are discussed as well.