The Solar Transition Region UltraViolet Explorer

We present the results of the NASA-funded concept study of the Solar Transition Region UltraViolet Explorer (STRUVE) CubeSat mission. STRUVE is a slit-scanning, full-Stokes spectropolarimeter that observes the Sun in the near-UV in the wavelength band recently identified by Judge et al. (2021) as a particularly promising region for diagnostics of chromospheric magnetic field. The observed wavelength region contains the well-known Mg II h and k lines as well as a plethora of Fe I and II lines that together will allow diagnostics of the magnetized plasma in the volume of the solar atmosphere from the photosphere through the chromosphere, and up to the transition region at the base of the corona. This capability is unprecedented, and highly relevant for an improved description of the magnetically connected solar atmosphere. The main objective of STRUVE is to advance our understanding of the energy build-up and storage in the solar atmosphere, and its eventual release through flares and coronal mass ejections.