  In order to quantify the influence of magnetic fields on acoustic mode
parameters and flows in and around active regions, we analyse the differences
in the parameters in magnetically quiet regions nearby an active region (which
we call `nearby regions'), compared with those of quiet regions at the same
disc locations for which there are no neighboring active regions. We also
compare the mode parameters in active regions with those in comparably located
quiet regions. Our analysis is based on ring diagram analysis of all active
regions observed by HMI during almost five years. We find that the frequency at
which the mode amplitude changes from attenuation to amplification in the quiet
nearby regions is around 4.2 mHz, in contrast to the active regions, for which
it is about 5.1 mHz. This amplitude enhancement (the `acoustic halo effect') is
as large as that observed in the active regions, and has a very weak dependence
on the wave propagation direction. The mode energy difference in nearby regions
also changes from a deficit to an excess at around 4.2 mHz, but averages to
zero over all modes. The frequency difference in nearby regions increases with
increasing frequency until a point at which the frequency shifts turn over
sharply as in active regions. However, this turnover occurs around 4.9 mHz,
significantly below the acoustic cutoff frequency. Inverting the horizontal
flow parameters in the direction of the neighboring active regions, we find
flows that are consistent with a model of the thermal energy flow being blocked
directly below the active region.
