SWAPI (Solar Wind and Pickup Ions)


Cross-sectional view of the SWAPI sensor with blue trajectories that highlight the incident solar wind and green that highlight PUIs. Yellow trajectories show the path of the secondary electrons generated from the foil to provide the coincidence timing.

The Solar Wind and Pickup Ion (SWAPI) instrument measures solar wind H+ and He++ and interstellar He+ and H+ Pickup Ions (PUIs). SWAPI is nearly identical to the Solar Wind Around Pluto (SWAP) instrument aboard New Horizons, which has over a decade of flight-proven observations of solar wind and PUI distributions. SWAPI is a simplification of SWAP, and by removal of SWAP’s retarding potential analyzer, significantly increases transmission and improves sensitivity, further enhancing PUI observations. Detailed measurements of these populations are fundamental to understanding the solar wind context, sources and acceleration of particles, PUIs, and the physical processes regulating the global heliosphere. SWAPI delivers the high time and energy resolution required to identify local acceleration processes.

By properly masking the sunward direction, SWAPI makes critical measurements of the solar wind conditions at 1 AU, including H+, He++, and heavier ions during cold solar wind conditions such as in many interplanetary coronal mass ejections (ICMEs). Away from the solar wind direction, there is no aperture reduction, increasing PUI sensitivity by 5× compared to SWAP. The SWAPI energy range is extended up to 20 keV/q to capture the 1D He+ and H+ PUI distributions and cutoffs, as well as both the solar wind H+ and He++.

All schematics and numbers are preliminary as of the beginning of Phase A. Additional information about each instrument can be found in the Open Access IMAP Paper.

SWAPI Instrument Table

SWAPI Instrument Performance.