Solar Wind and Pickup Ions (SWAPI) Technical Overview

SWAPI measures several different elements of the A stream of charged particles, mostly protons and electrons, that escapes into the Sun's outer atmosphere at high speeds and streams out into the solar system in all directions., including hydrogen (H) and helium (He) ions, and, on occasion, heavy ions produced by large events from the Sun. The Solar Wind and Pickup Ion (SWAPI) instrument collects and counts solar wind particles and pick-up ions (PUIs). also measures interstellar pickup ions (PUIs), whose material comes from beyond our solar system and moves along with the solar wind. Its data provides information about the local An atom that has become electrically charged by the gain or loss of one or more electrons. conditions, such as A measure of the average random speeds of the microscopic particles in a substance., The amount of mass or number of particles per unit volume. In cgs units, mass density has units of gm cm-3. Number density has units cm-3 (particles per cubic centimeter)., and speed. This is also used in the The IMAP Active Link for Reat-Time (I-ALiRT) system provides a high-cadence stream of near-real time space weather data from the HIT, CoDICE, SWAPI, SWE, and MAG instruments to scientists on Earth via a network of antenna partners located around the globe, including the DSN. This enhanced data stream will assist in improving overall reliability and timing of Earthbound space weather predictions, providing data to forecasters in time for users to take protective action. data stream allowing The conditions and activity observed in interplanetary space caused by the Sun’s activity, such as solar flares, solar storms, and coronal mass ejections (CMEs). Severe space weather conditions directed towards Earth can impact infrastructure and technology on Earth, as well as satellites, spacecraft, and astronauts in its trajectory. to be measured in real-A measure of the flow of events.. The data from SWAPI is valuable for understanding how the solar wind changes in response to the Sun’s behavior over time. SWAPI’s first-ever high time resolution measurements of helium PUIs provide new insights into physical processes that accelerate charged particles and shape and change our global The bubble-like region surrounding the solar system inflated by the solar wind, shielding the solar system from interstellar radiation..

At L1, where IMAP observes, the solar wind is colder but much more intense than the hotter PUIs. The solar wind particles flow mainly in one direction while PUIs enter SWAPI from all directions. SWAPI's entrance structure is designed to sort out these particles. First, the particles pass through "sunglasses” that decrease the solar wind by a factor of a thousand, and then through vanes that block deflected solar wind from overwhelming the weaker PUI signal.

SWAPI design and assembly is led by Princeton University.

The Solar Wind and Pick Up Ion (SWAPI) instrument designed to collect solar wind and pick up ions. A grey metallic disc base supports a gold cylindrical structure. Cables loop from the base to the top of the cylinder secured by blue ties. A silver metal collar with evenly-spaced rectangular windows extends out between the cylinder and a black baffle with two angular vane panels extend outward shielding the instrument opening. The background is a clean, white environment.

The Solar Wind and Pickup Ion (SWAPI) instrument is shown before installation onto the Interstellar Mapping and Acceleration Probe (IMAP) at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland. 

Image Credit: NASA/Johns Hopkins APL/Princeton/Ed Whitman

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

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.