FIERCE Science: Expected Results From a High-Energy Medium-Class Explorer

A variety of individual X-ray and EUV instruments have probed high-energy aspects of the Sun over the decades, each contributing pieces to the puzzles of the energization, heating, and acceleration of solar plasma and particles. But fundamental difficulties in sensitivity and dynamic range impart big challenges in probing the details of particle acceleration sites, understanding how eruptions and flares are initiated, and tracking the intricacies of energy transfer as flares evolve. The Fundamentals of Impulsive Energy Release in the Corona Explorer ( FIERCE ) mission will make substantial leaps forward in these scientific ventures by combining a variety of instruments into one platform, each optimized to have high sensitivity and dynamic range. FIERCE is a proposed NASA Heliophysics Medium-Class Explorer that will investigate high-energy solar phenomena across a variety of spectral and spatial dimensions. It combines hard X-ray imaging spectroscopy (via focusing, for the first time for a solar-dedicated spacecraft), spatially integrated soft X-ray spectroscopy, and fast, high-resolution extreme ultraviolet imaging at coronal and flare temperatures. FIERCE uses this array of instruments to make important contributions toward probing the genesis of space weather events, the acceleration of particles, the transport of flare energy, and the heating of the corona. Here, we present some of the expected science outcomes for the FIERCE observatory, concentrating on the ways in which FIERCE can probe confined and eruptive events, particle acceleration everywhere it may occur on the Sun, and the connections of solar high-energy phenomena to the heliosphere.