  Optical and near-UV continuum emissions in flares contribute substantially to
flare energy budget. Two mechanisms play an important role for continuum
emission in flares: hydrogen recombination after sudden ionization at
chromospheric layers and transportation of the energy radiatively from the
chromosphere to lower layers in the atmosphere, the so called back-warming. The
aim of the paper is to disentangle between these two mechanisms for the excess
of Balmer continuum observed in a flare. Methods. We combine the observations
of Balmer continuum obtained with IRIS (spectra and SJIs 2832 A) and hard X-ray
(HXR) emission detected by FERMI Gamma Burst Monitor (GBM) during a mini flare.
Calibrated Balmer continuum is compared to non-LTE radiative transfer flare
models and radiated energy is estimated. Assuming thick target HXR emission, we
calculate the energy of non-thermal electrons detected by FERMI GBM and compare
it to the radiated energy. The favorable argument of a relationship between the
Balmer continuum excess and the HXR emission is that there is a good time
coincidence between both of them. In addition, the shape of the maximum
brightness in the 2832 SJIs, which is mainly due to this Balmer continuum
excess, is similar to the FERMI/GBM light curve. The electron-beam flux
estimated from FERMI/GBM is consistent with the beam flux required in non-LTE
radiative transfer models to get the excess of Balmer continuum emission
observed in the IRIS spectra. The low energy input by non thermal electrons
above 20 keV is sufficient to produce the enhancement of Balmer continuum
emission. This could be explained by the topology of the reconnection site. The
reconnection starts in a tiny bald patch region which is transformed
dynamically in a X-point current sheet. The size of the interacting region
would be under the spatial resolution of the instrument.
