Imaging Three-Dimensional Heliosphere in EUV with Ultra-High Spectral Resolution

A high-throughput, high-resolution spectrometer for diffuse radiation at 30.4 nm allows a way to map the heliopause and to image the three-dimensional flow pattern of the solar wind, including in the regions over the sun's poles. The radiation reaching an observer would include glow of the interstellar plasma beyond the heliopause and emissions produces by charge exchange of solar wind alpha-particles on interplanetary atomic hydrogen. We show that high spectral resolution would separate these two sources of radiation and distinguish between the high (ecliptic) and slow (polar) solar wind flows. This enabling instrumentation should be able to measure 1 milli-Rayleigh irradiance in 1000 seconds with a 0.005-nm spectral resolution with an angular pixel of a few degrees. The desired performance characteristics can be achieved by combining multiple entrance slits with an optimized spectrometer design.