  Solar flares show remarkable variety of the energy partitioning between
thermal and nonthermal components. Those with a prominent nonthermal component
but only a modest thermal one are particularly well suited to study the direct
effect of the nonthermal electrons on plasma heating. Here, we analyze such a
well observed, impulsive single-spike nonthermal event, a SOL2013-11-05T035054
solar flare, where the plasma heating can be entirely attributed to the energy
losses of these impulsively accelerated electrons. Evolution of the energy
budget of thermal and nonthermal components during the flare is analysed using
X-ray, microwave, and EUV observations and three-dimensional modeling. The
results suggest that (i) the flare geometry is consistent with a two-loop
morphology and the magnetic energy is likely released due to interaction
between these two loops; (ii) the released magnetic energy converted to the
nonthermal energy of accelerated electrons only, which is subsequently
converted to the thermal energy of the plasma; (iii) the energy is partitioned
in these two flaring loops in comparable amounts; (iv) one of these flaring
loops remained relatively tenuous but rather hot, while the other remained
relatively cool but denser than the first one. Therefore, this solar flare
demonstrates an extreme efficiency of conversion of the free magnetic energy to
the nonthermal energy of particle acceleration and the energy flow into two
loops from the non-thermal to thermal one with a negligible direct heating.
