The Signature of Explosive Events in the FUV Spectrum of the Sun as a Star

A NASA suborbital sounding rocket mission known as the Full-sun Ultraviolet Rocket SpecTrometer (FURST) is being developed for launch in late 2021 and will obtain the first high-resolution, high-quality VUV spectrum of the Sun as a star. FURST will open new insights into solar activity, placing the Sun in context with other stars. FURST spectra will also have broad applications in solar system and climate science. One of the science goals of FURST is the detection of explosive events (EEs) in the solar transition region (TR). EEs appear as suprathermal broadenings in TR emission line observations. If the disk-integrated signature of EEs in the wings of TR emission lines can be clearly separated from continuum and instrumental backgrounds, then it will open a window to comparing solar and stellar atmospheres in quiescent (non-flaring) conditions. In an effort to learn whether this may be accomplished with existing solar data (albeit in a narrow spectral window), we have identified EEs in monthly Interface Region Imaging Spectrograph (IRIS) full-disk mosaics (FDMs), and quantified their contribution to the full-disk integrated spectrum in strong TR lines. The integrated IRIS FDM spectra can be compared directly to Hubble Space Telescope (HST) spectra of Sun-like stars.