Distribution of kT_LHB in the high latitude regions (|b| > 30°). The unfilled histogram outlined in black displays the distribution of all the high latitude bins displayed in Fig. 8. The black dashed line shows the Gaussian best fit for the distribution. The black data point with error bars shows the typical (median) 1σ spectral fitting uncertainty, centred at the mean of the fitted Gaussian. It is plotted at a height of exp (−1/2)N_gauss,peak = 0.606 N_gauss,peak for proper comparison between the spectral fitting uncertainty and the width of the distribution. The former (0.010 keV) is approximately half of the latter (0.018 keV), demonstrating a genuine variation in the LHB temperature. The sample is divided into the northern (orange) and the southern (green) Galactic hemispheres to demonstrate the primary source of variation is a large-scale gradient instead of small-scale fluctuations. The northern hemisphere is cooler (0.100 keV) than the south (0.122 keV), and comparing their distributions with the respective typical spectral fitting uncertainties shows that each hemisphere exhibits approximately constant LHB temperature.