Temporal intermittency of energy dissipation in magnetohydrodynamic turbulence.
Energy dissipation in magnetohydrodynamic (MHD) turbulence is known to be highly intermittent in space, being concentrated in sheetlike 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 or 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 α≈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.
Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, Wisconsin 53706, USA.
Vladimir
V
Zhdankin
Center for Integrated Plasma Studies, Physics Department, UCB-390, University of Colorado, Boulder, Colorado 80309, USA.
Dmitri A
DA
Uzdensky
Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, Wisconsin 53706, USA.
Stanislav
S
Boldyrev