A co-authored paper accepted earlier this year is now online! The paper "Suprathermal Ions in the Outer Heliosphere" compares the energy spectra of suprathermal pick-up ions as a function of radial distance from the Sun as well as solar cycle phase using both Cassini and New Horizons. Since very few missions have explored the heliosphere this far from the sun, these measurements provide insight into energization processes.
To quote the abstract:
"We find that the power-law exponents of suprathermal ion intensity over energy are between −1 and −2, change abruptly close to discontinuities that are likely corotating merged interaction regions, correlate with the solar wind bulk speed, and show a long-term evolution on the timescale of the solar cycle."