with the widths fixed to the instrumental resolution. We fixed the centroid to its laboratory value of 0.6536 keV, but let the centroid vary since the line is an unresolved blend of the resonance, forbidden, and intercombination lines. The Gaussian normalizations were also free parameters, because these represent the line strength measurements. We point out that this spectral fitting method measures the *total* emission line strengths from all emission sources (residual SWCX, LB, absorbed hot gas halo, or Fermi bubble) for each sight line. This is why our model line intensities in Section \[subsection.intensity\_chap\_fb\] include all emission sources along each sight line.

The Exclusion of the North Polar Spur Region {#subsection.nps}
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The North Polar Spur (NPS) is an extended region of enhanced X-ray emission that is cospatial with part of a larger region of enhanced radio continuum emission known as Loop I [@berkhuijsen_etal71; @borken_iwan77; @snowden_etal97]. The X-ray enhancement is strongest at lower Galactic latitudes near $l, b \approx$ 25, 25, and gradually decreases in intensity toward the Galactic pole. Spectral observations with *XMM-Newton* and *Suzaku* indicate that the plasma is hotter than the surrounding medium with $kT \approx 0.3$ keV, is depleted in C, O, Mg, Ne, Fe, and 