Do EUV nanoflares account for coronal heating?

Recent observations with EUV imaging instruments such as SOHO/EIT and TRACE have shown evidence for flare-like processes at the bottom end of the energy scale, in the range of E-th approximate to 10(24)-10(27) erg. Here we compare these EUV nanoflares with soft X-ray microflares and hard X-ray flares across the entire energy range. From the observations we establish empirical scaling laws for the flare loop length, L(T) similar to T, the electron density, n(e)(T) similar to T-2, from which we derive scaling laws for the loop pressure, p(T) similar to T-3, and the thermal energy, E-th similar to T-6. Extrapolating these scaling laws into the picoflare regime we find that the pressure conditions in the chromosphere constrain a height level for flare loop footpoints, which scales with h(eq)(T) similar to T-0.5. Based on this chromospheric pressure limit we predict a lower cutoff of flare loop sizes at L-min less than or similar to 5 Mm and flare energies E-min less than or similar to 10(24) erg. We show evidence for such a rollover in the flare energy size distribution from recent TRACE EUV data. Based on this energy cutoff imposed by the chromospheric boundary condition we find that the energy content of the heated plasma observed in EUV, SXR, and HXR flares is insufficient (by 2-3 orders of magnitude) to account for coronal heating.