Solar ENA Imaging Coronagraph Project

Observations of energetic neutral atoms (ENAs) provide the only way to observe solar energetic particles (SEPs) where they are accelerated. The one observation of solar ENAs to date had low sensitivity, a high energy threshold, and no imaging information. The Solar Energetic Neutral-atom Imaging Coronagraph (SENIC) instrument concept combines large detector area, a low energy threshold, and high angular resolution. The key design challenge for this concept was to minimize the level of stray light illuminating the detectors.
 

Measurements of energetic neutral atoms (ENAs) are a new tool to improve our understanding of energy release and particle acceleration in solar eruptive events.  Due to limitations of past observations, even the most basic questions remain unanswered about the acceleration of solar energetic particles (SEPs) by shocks driven by coronal mass ejections (CMEs).  ENAs provide the only way to observe SEPs where they are accelerated.  The one observation of solar ENAs to date had low sensitivity, a high energy threshold, and no imaging information. The Solar Energetic Neutral-atom Imaging Coronagraph (SENIC) instrument concept is designed to observe ENAs from <~20 keV to a few hundred keV with a spectral resolution as good as 1 keV and image them from 2 R_sun to 40 R_sun with a spatial resolution of 0.1 R_sun.  Since ENAs cannot be imaged with focusing optics, this concept uses an indirect imaging technique similar to the one successfully used on RHESSI.  Thus, the SENIC instrument concept combines large detector area, a low energy threshold, and high angular resolution.