  The heliospheric magnetic field (HMF) is structured into large sectors of
positive and negative polarity. The parts of the boundary between these sectors
where the change in polarity matches that of the leading-to-following sunspot
polarity in that solar hemisphere, are called Hale Sector Boundaries (HSB). We
investigate the flare occurrence rate near HSBs and the association between
HSBs and active longitudes. Previous work determined the times HSBs were at
solar central meridian, using the detection of the HMF sector boundary crossing
at the Earth. In addition to this, we use a new approach which finds the HSB
locations at all times by determining them from Potential Field Source Surface
(PFSS) extrapolations of photospheric magnetograms. We use the RHESSI X-ray
flare list for comparison to the HSB as it provides accurate flare locations
over 14 years, from February 2002 to February 2016, covering both Cycles 23 and
24. For the active longitude positions we use previously published work based
on sunspot observations. We find that the two methods of determining the HSB
generally agree and that 41% (Cycle 23) and 47% (Cycle 24) of RHESSI flares
occur within $30^\circ$ of the PFSS determined-HSB. The behaviour of the HSBs
varies over the two Cycles studied, and as expected they swap in hemisphere as
the Cycles change. The HSBs and active longitudes do overlap but not
consistently. They often move at different rates relative to each other (and
the Carrington solar rotation rate) and these vary over each Cycle. The HSBs
provide a useful additional activity indicator, particularly during periods
when active longitudes are difficult to determine.
