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

We focus on determining the time evolution of the Local Interstellar Medium (LISM) longitudinal inflow direction through the Heliosphere over greater than a decade of in situ measurement data. 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 (PUI) measurements from mass spectrometers such as ACE/SWICS and STEREO/PLASTIC as they cross the focusing cone. Pickup ion transport along the IMF is neglected by selecting measurement times when the PUI torus is in the instrument field of view. Solar transients are also accounted for using methods such as correcting for compression regions and rejecting CMEs. Mapping from the He ⁺ peak to the Sun, around which the helium is focused, directly yields the desired longitudinal direction.