  A magnetic power spectral analysis is performed on 53 solar active regions,
observed from August 2011 to July 2012. Magnetic field data obtained from the
Helioseismic and Magnetic Imager, inverted as Active Region Patches, are used
to study the evolution of the magnetic power index as each region rotates
across the solar disk. Active regions are classified based on the number, and
sizes, of solar flares they produce, in order to study the relationship between
flare productivity and the magnetic power index. The choice of window size and
inertial range plays a key role in determining the correct magnetic power
index. The overall distribution of magnetic power indices has a range of
$1.0-2.5$. Flare-quiet regions peak at a value of 1.6, however flare-productive
regions peak at a value of 2.2. Overall, the histogram of the distribution of
power indices of flare-productive active regions is well separated from
flare-quiet active regions. Only 12\% of flare-quiet regions exhibit an index
greater than 2, whereas 90\% of flare-productive regions exhibit an index
greater than 2. Flare-quiet regions exhibit a high temporal variance (i.e, the
index fluctuates between high and low values), whereas flare-productive regions
maintain an index greater than 2 for several days. This shows the importance of
including the temporal evolution of active regions in flare prediction studies,
and highlights the potential of a 2-3 day prediction window for space weather
applications.
