SWE measures the 3D The number of specified items or components found in a defined space. of highly energetic electrons found in 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.. The Solar Wind Electron (SWE) instrument collects and counts electrons from the solar wind in a range of energies from 0.2-2000 electron volts (eVs). is optimized to measure in situ solar wind electrons at L1 to provide context for the ENA measurements and perform the in situ solar wind observations necessary to understand the local structures that can affect acceleration and transport of these particles.
SWE consists of a curved-plate electrostatic analyzer (ESA) composed of nested 120° spherical, grooved, and blackened aluminum alloy plates, and seven channel A negatively charged elementary particle that normally resides outside (but is bound to) the nucleus of an atom. multiplier (CEM) detectors. Electrons enter the ESA through a fan-shaped aperture directed radially out the side of the IMAP spacecraft. This entry point is engineered such that only electrons within a narrow range of energies and directions (angles) pass through and are detected. Each CEM An instrument which is used to discover that something is present somewhere, or to measure how much of something there is. possesses a fan-shaped field of view (FOV) that allows the instrument to view the entire strip of sky parallel to the instrument as the IMAP spacecraft spins, missing only a few small areas. The high resolution of energies and flow angles allow for a full characterization of the solar wind electron distributions that include an energy Electromagnetic radiation arranged in order of wavelength. A rainbow is a natural spectrum of visible light from the Sun. Spectra are often punctuated with emission or absorption lines, which can be examined to reveal the composition and motion of the radiating source. of energetic particle populations.
SWE - together with SWAPI, MAG, CoDICE, and HIT - also provides near real-A measure of the flow of events. measurements for the IMAP Active Link for Real-Time (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.) 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. monitoring service. With I-ALiRT, IMAP enables new ways of forecasting space weather by streaming near real-time observations of conditions headed towards Earth to operators on the ground, increasing our awareness and understanding of space weather drivers before they can reach Earth.
SWE design and assembly is led by Los Alamos National Laboratory (LANL) in collaboration with Southwest Research Institute (SwRI).

The Solar Wind Electron (SWE) instrument before installation to the Interstellar Mapping and Acceleration Probe (IMAP) spacecraft at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland.
Image Credit: NASA/Johns Hopkins APL/Ed Whitman

IMAP-SWE schematic.