  Extreme-ultraviolet late phase (ELP) refers to the second extreme-ultraviolet
(EUV) radiation enhancement observed in certain solar flares, which usually
occurs tens of minutes to several hours after the peak of soft X-ray emission.
The coronal loop system that hosts the ELP emission is often different from the
main flaring arcade, and the enhanced EUV emission therein may imply an
additional heating process. However, the origin of the ELP remains rather
unclear. Here we present the analysis of a C1.4 flare that features such an
ELP, which is also observed in microwave wavelengths by the Expanded Owens
Valley Solar Array (EOVSA). Similar to the case of the ELP, we find a gradual
microwave enhancement that occurs about three minutes after the main impulsive
phase microwave peaks. Radio sources coincide with both footpoints of the ELP
loops and spectral fits on the time-varying microwave spectra demonstrate a
clear deviation of the electron distribution from the Maxwellian case, which
could result from injected nonthermal electrons or nonuniform heating to the
footpoint plasma. We further point out that the delayed microwave enhancement
suggests the presence of an additional heating process, which could be
responsible for the evaporation of heated plasma that fills the ELP loops,
producing the prolonged ELP emission.

Solar and Stellar Astrophysics