Determining the Interstellar Wind Longitudinal Inflow Evolution Using Pickup Ions in the Helium Focusing Cone

We investigate the time evolution of the local interstellar medium longitudinal inflow direction through the Heliosphere over the decades of in situ measurement data collected. This direction directly correlates to the orientation of the helium focusing cone with respect to the Sun. We can calculate this direction using He⁺ pickup ion measurements from mass spectrometers such as Wind/STICS, ACE/SWICS, and STEREO/PLASTIC as they cross the cone. Pickup ion transport along the IMF is neglected by selecting only newly injected pickup ions. Solar transients are also accounted for using methods such as averaging and accounting for CMEs. Mapping from the He⁺ peak to the Sun, around which the helium is focused, directly yields the desired longitudinal direction. We present measurements of the inflow direction over the two decades spanned by the Wind, ACE, and STEREO missions.