  Energy dissipation in magnetohydrodynamic (MHD) turbulence is known to be
highly intermittent in space, being concentrated in sheet-like coherent
structures. Much less is known about intermittency in time, another fundamental
aspect of turbulence which has great importance for observations of solar
flares and other space/astrophysical phenomena. In this Letter, we investigate
the temporal intermittency of energy dissipation in numerical simulations of
MHD turbulence. We consider four-dimensional spatiotemporal structures, "flare
events", responsible for a large fraction of the energy dissipation. We find
that although the flare events are often highly complex, they exhibit robust
power-law distributions and scaling relations. We find that the probability
distribution of dissipated energy has a power law index close to -1.75, similar
to observations of solar flares, indicating that intense dissipative events
dominate the heating of the system. We also discuss the temporal asymmetry of
flare events as a signature of the turbulent cascade.
