Solar cycle variations in the composition of the suprathermal heavy-ion population near 1 AU

We have measured the annual variation in the quiet-time composition of interplanetary suprathermal ions between 0.04 and 1 MeV nucleon(-1) from 1994 November 20 through 2006 January 1. Our results show the following: ( 1) The C/O and Fe/O ratios are similar to the corresponding values measured in the solar wind and corotating interaction regions (CIRs) during solar minimum conditions of 1994-1997 and 2005. ( 2) During periods of increased solar activity between 1998 and 2002, the C/O ratio is similar to that measured in solar energetic particle (SEP) events, while the Fe/O ratio lies between the values measured in coronal mass ejection driven interplanetary shock and SEP events. ( 3) The He-3/He-4 ratio lies in the 1.5%-5% range during 1997-2005 August, but it dropped by an order of magnitude during 2005. We conclude that the composition of the suprathermal ion population between similar to 6 and 30 times the solar wind speed near 1 AU is dynamic and is essentially dominated by ions accelerated in SEP events during solar maximum conditions and by suprathermal solar wind ions and/or those accelerated in CIRs during solar minimum conditions.