Energetics of transient brightenings. Top panel: black curve shows the frequency distribution of the energy of the transient brightenings detected at 1.26 mm. The gray band denotes the uncertainties (see text for details). The red line shows the power-law fit, with index of 1.64, of the frequency distribution for energies higher than 2.7 × 10²³ erg. Bottom panel: same as top panel for the events detected at 3 mm. The red line shows the power-law fit, with index of 1.73, of the frequency distribution for energies higher than 10²⁴ erg.