Intensity Variations of the Soft X-ray Background: the Boundary Structure of the Local Hot Bubble at Low Galactic Latitudes

42 ROSAT PSPC pointed observations in the Galactic plane (l ∼ 4° – 26°) are mosaicked in order to study the spatial structure of the X-ray emitting gas in the Local Hot Bubble (LHB). Degree scale X-ray intensity variations are detected at the ± 10% level in the 1/4 keV band, which imply a likely influence from a clumpy boundary shell of the LHB in the observed 1/4 keV band X-ray background. The possible origins of such a clumpy boundary structure of the LHB are discussed.