  Solar flares are a fundamental component of solar eruptive events (SEEs;
along with solar energetic particles, SEPs, and coronal mass ejections, CMEs).
Flares are the first component of the SEE to impact our atmosphere, which can
set the stage for the arrival of the associated SEPs and CME. Magnetic
reconnection drives SEEs by restructuring the solar coronal magnetic field,
liberating a tremendous amount of energy which is partitioned into various
physical manifestations: particle acceleration, mass and magnetic-field
eruption, atmospheric heating, and the subsequent emission of radiation as
solar flares. To explain and ultimately predict these geoeffective events, the
heliophysics community requires a comprehensive understanding of the processes
that transform and distribute stored magnetic energy into other forms,
including the broadband radiative enhancement that characterises flares. This
white paper, submitted to the Heliophysics 2050 Workshop, discusses the flare
gradual phase part of SEEs, setting out the questions that need addressing via
a combination of theoretical, modelling, and observational research. In short,
the flare gradual phase persists much longer than predicted so, by 2050, we
must identify the characteristics of the significant energy deposition
sustaining the gradual phase, and address the fundamental processes of
turbulence and non-local heat flux.
