Nonthermal electron energy deposition in the chromosphere and the accompanying soft X-ray flare emission

We analyse four solar flares which have energetic hard X-ray emissions, but unusually low soft X-ray flux and GOES class (C1.0-C5.5). These are compar ed with two other flares that have soft and hard X-ray emission consistent with a generally observed correlation that shows increasing hard X-ray acco mpanied by increasing soft X-ray flux. We find that in the four small flare s only a small percentage of the nonthermal electron beam energy is deposit ed in a location where the heating rate of the electron beam exceeds the ra diative cooling rate of the ambient plasma. Most of the beam energy is subs equently radiated away into the cool chromosphere and so cannot power chrom ospheric evaporation thus reducing the soft X-ray emission. We also demonst rate that in the four small flares the nonthermal electron beam energy is i nsufficient to power the soft X-ray emitting plasma. We deduce that an addi tional energy source is required, and this could be provided by a DC-electr ic field (where quasi-static electric field channels in the coronal loops a ccelerate electrons, and those electrons with velocity below a critical vel ocity will heat the ambient plasma via Joule heating) in preference to a lo op-top thermal source (where heat flux deposited in the corona is conducted along magnetic field lines to the chromosphere, heating the coronal plasma and giving rise to further chromospheric evaporation).