  The Galactic Center (GC) is surrounded by plasma lobes that extend up to ~14
kpc above and below the plane. Until now, UV absorption studies of these lobes
have only focused on high-velocity components (|v_LSR| > 100 km/s) because low-
and intermediate-velocity (LIV) components (|v_LSR| <100 km/s) are blended with
foreground interstellar medium. To overcome this difficulty, we present a
differential experiment to compare the LIV absorption between different
structures within the GC region, including the Fermi Bubbles (FBs; seen in
gamma-rays), the eROSITA Bubbles (eBs; seen in X-rays), and the Loop I North
Polar Spur (LNPS) association, an X-ray and radio feature within the northern
eB. We use far-UV spectra from Hubble Space Telescope to measure LIV Si IV
absorption in 61 AGN sight lines, of which 21 pass through the FBs, 53 pass
through the eBs, and 18 pass through the LNPS. We also compare our measurements
to those in the literature from sight lines covering the disk-halo interface
and CGM. We find that the FBs and eBs have enhancements in measured columns of
0.22-0.29 dex in log. We also remove the contribution of a modeled disk and CGM
component from the measured Si IV columns and find that the northern eB still
retains a Si IV enhancement of 0.62 dex in log. A similar enhancement is not
seen in the southern eB. Since the LNPS model-subtracted residuals show an
enhancement compared to the rest of the northern eB of 0.69 dex, the northern
eB enhancement may be caused by the LNPS.
