The MUlti-slit Solar Explorer (MUSE)

The Multi-slit Solar Explorer (MUSE) is a recently selected NASA MIDEX mission, composed of a multi-slit EUV spectrograph (in three narrow spectral bands centered around 171Å, 284Å, and 108Å) and an EUV context imager (in two narrow passbands around 195Å and 304Å). MUSE will provide unprecedented spectral and imaging diagnostics of the solar corona at high spatial (~0.5 arcseconds), and temporal resolution (down to ~0.5 seconds) thanks to its innovative multi-slit design. By obtaining spectra in 4 bright EUV lines (Fe IX 171Å, Fe XV 284Å, Fe XIX-XXI 108Å) covering a wide range of transition region and coronal temperatures along 37 slits simultaneously, MUSE will for the first time be able to "freeze" (at a cadence as short as 10 seconds) with a spectroscopic raster the evolution of the dynamic coronal plasma over a wide range of scales: from the spatial scales on which energy is released (<0.5 arcsec) to the large-scale often active-region size (~ 170 arcsec × 170 arcsec) atmospheric response. We use advanced numerical modeling to showcase how MUSE will constrain the properties of the solar atmosphere on the spatio-temporal scales (<0.5 arcsec, <20 seconds) and large field-of-view on which various state-of-the-art models of the physical processes that drive coronal heating, solar flares and coronal mass ejections (CMEs) make distinguishing and testable predictions. We describe how the synergy between MUSE, the single-slit, high-resolution Solar-C EUVST spectrograph, and ground-based observatories (DKIST and others) can address how the solar atmosphere is energized, and the key role MUSE plays because of the multi-scale nature of the physical processes involved.