  We present a volume-sensitive high-energy x-ray diffraction study of the
underdoped cuprate high temperature superconductor La2-xSrxCuO4 (x = 0.12,
Tc=27 K) in applied magnetic field. Bulk short-range charge stripe order with
propagation vector q_ch = (0.231, 0, 0.5) is demonstrated to exist below T_ch =
85(10) K and shown to compete with superconductivity. We argue that bulk charge
ordering arises from fluctuating stripes that become pinned near boundaries
between orthorhombic twin domains.
