  In this paper we examine suprathermal He ions measured by the SIT
(Suprathermal Ion Telescope) instrument associated with tilted corotating
interaction regions (CIRs). We use observations of the two STEREO spacecraft
(s/c) for the first 2.7 years of the mission, along with ground-based
measurements of the solar magnetic field during the unusually long minimum of
Solar Cycle 23. Due to the unique configuration of the STEREO s/c orbits we are
able to investigate spatial variations in the intensity of the corotating ions
on time scales of less than one solar rotation. The observations reveal that
the occurrence of the strong CIR events was the most frequent at the beginning
of the period. The inclination of the heliospheric current sheet relative to
the heliographic equator (the tilt angle) was quite high in the first stage of
the mission and gradually flattened with the time, followed by a decrease in
the CIR activity. By examining the differences between measurements on the two
STEREO s/c we discuss how the changes in the position of the s/c relative to
the CIRs affect the energetic particle observations. We combine STEREO
observations with observations from the ULEIS instrument on the ACE s/c and
argue that the main factor which controls the differences in the ion
intensities is the latitudinal separation between the two STEREO s/c relative
to the tilted CIRs. The position of the s/c is less important when the tilt
angle is high. In this case we found that the CIR ion intensity positively
correlates with the tilt angle.
