  Parker (1972) first proposed that coronal heating was the necessary outcome
of an energy flux caused by the tangling of coronal magnetic field lines by
photospheric flows. In this paper we discuss how this model has been modified
by subsequent numerical simulations outlining in particular the substantial
differences between the "nanoflares" introduced by Parker and "elementary
events", defined here as small-scale spatially and temporally isolated heating
events resulting from the continuous formation and dissipation of field-aligned
current sheets within a coronal loop. We present numerical simulations of the
compressible 3-D MHD equations using the HYPERION code. We use two clustering
algorithms to investigate the properties of the simulated elementary events: an
IDL implementation of a Density-Based Spatial Clustering of Applications with
Noise (DBSCAN) technique; and our own Physical Distance Clustering (PDC)
algorithm. We identify and track elementary heating events in time, both in
temperature and in Joule heating space. For every event we characterize
properties such as: density, temperature, volume, aspect ratio, length,
thickness, duration and energy. The energies of the events are in the range
$10^{18}-10^{21}$ ergs, with durations shorter than 100 seconds. A few events
last up to 200 seconds and release energies up to $10^{23}$ ergs. While high
temperature are typically located at the flux tube apex, the currents extend
all the way to the footpoints. Hence a single elementary event cannot at
present be detected. The observed emission is due to the superposition of many
elementary events distributed randomly in space and time within the loop.
