The Dst index, and solar wind magnetic field (in GSE coordinates) and plasma parameters, for the July 15, 2012, geomagnetic storm with minimum Dst = −133 nT, associated with passage of a magnetic cloud with a southward magnetic field (B_Z < 0). The bottom panel shows the solar wind proton temperature (T_p, black) with the “expected” temperature (T_exp, red) superposed. T_exp is inferred from the T_p – solar wind speed relationship found in “normal” solar wind using the observed solar wind speed. The black shaded region indicates where T_p ≤ 0.5 T_exp, which is a frequent feature of magnetic clouds and other interplanetary coronal mass ejections (see Richardson & Cane 1995 for further details). OMNI 1-min solar wind data are shown; the fluctuations near shock passage are artifacts of the data mapping from the ACE spacecraft.