Upper limits for the solar wind He⁺content at 1 AU

An upper limit for the steady state solar wind He+ concentration is estimated from four Vela 5 and 6 heavy ion spectrums. The upper limit value for N(He+)/N(H) of 2.5 × 10−6 so obtained is at least an order of magnitude less than that predicted from presently accepted models of the local interstellar medium. The most likely explanation of the discrepancy is that wave-particle interactions are not capable of fully assimilating the initially non-Maxwellian high-temperature He+ particles of interstellar origin into the solar wind flow. Occasional flow conditions resulting in complete assimilation cannot be ruled out.