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

Abstract

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.

The abundance of atomic 1H, 4He and 3He in the local interstellar cloud from pickup ion observations with SWICS on Ulysses

“…First, the pickup proton spectrum extends all the way to the predicted cutoff at W = 2. This implies that there is little if any thermalization of pickup ions, that is, the coupling between the solar wind plasma and pickup ions is so weak that little energy is exchanged as was first discussed by Feldman et al (1974). Second, the drop-off of phase space density beyond the cutoff at W = 2 (corresponding to w = 1 in the solar wind frame) is very sharp, implying little if any energy diffusion.…”

Solar wind heavy ion abundances

“…Both a description of the instrumentation and data accumulation cycle Bame, 1972) as well as details of the numerous requirements to be fulfilled before a heavy ion spectrum is accepted for analysis (Bame, 1972;Bame et al, 1974;Feldman et al, 1974) have been presented elsewhere and will not be repeated here. Vela 5 and 6 heavy ion spectra measured between June 1969 and March 1972 were searched for acceptable samples of 'quiet' solar wind flow conditions (low velocity and low temperature).…”

“…In particular, measurements of average solar wind elemental ab undances provide information concerning the dynamics of the expanding, steady-state solar corona. For example theoretical studies of the coronal-chromosphere transition region (Jokipii, 1966;Nakada, 1969) and of the upper corona-solar wind (Nakada, 1970;Geiss et al, 1970a;Alloucherie, 1970) suggest there may be a steady-state accumulation of heavy elements in the low solar corona. However, these studies did not consider quantitatively the contribution of waves or turbulent mixing processes to the steady-state coronal abundance configuration.…”

Solar wind heavy ions from flare-heated coronal plasma

“…If the He peak is narrow, a peak of 0 7+ ions at position A is resolved. Other examples of IS spectra can be found in Bame et al ( , 1974Bame et al ( , 1975, Feldman et al (1974).…”