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We investigate several key questions of plasma heating in open-field regionsof the corona that connect to the solar wind. We present results for a model ofAlfven-wave-driven turbulence for three typical open magnetic field structures:a polar coronal hole, an open flux tube neighboring an equatorial streamer, andan open flux tube near a strong-field active region. We compare time-steady,one-dimensional turbulent heating models (Cranmer et al., 2007) against fullytime-dependent three-dimensional reduced-magnetohydrodynamics modeling of BRAID(van Ballegooijen et al., 2011). We find that the time-steady results agreewell with time-averaged results from BRAID. The time-dependence allows us toinvestigate the variability of the magnetic fluctuations and of the heating inthe corona. The high-frequency tail of the power spectrum of fluctuations formsa power law whose exponent varies with height, and we discuss the possiblephysical explanation for this behavior. The variability in the heating rate isbursty and nanoflare-like in nature, and we analyze the amount of energy lostvia dissipative heating in transient events throughout the simulation. Theaverage energy in these events is 10^21.91 erg, within the "picoflare" range,and many events reach classical "nanoflare" energies. We also estimated themultithermal distribution of temperatures that would result from theheating-rate variability, and found good agreement with observed widths ofcoronal differential emission measure (DEM) distributions. The results of themodeling presented in this paper provide compelling evidence that turbulentheating in the solar atmosphere by Alfven waves accelerates the solar wind inopen flux tubes.

Time-Dependent Turbulent Heating of Open Flux Tubes in the Chromosphere, Corona, and Solar Wind