星际弥散介质（ISM）是动态的，其化学性质和演化取决于激波前沿和光解离。超音速运动和速度分散（通常在统计上称为“湍流”）暗示了冲击。我们比较了磁流体动力（MHD）冲击的模型，通过ISM的云运动的典型速度（3-25 km s
-1
）和冷中性气体的典型密度（约10
2
cm
-3
）与H的档案观测值。
我
21厘米线用于气体运动学，为尘埃块发射远红外，中红外发射用于高分辨率的形态，以确定与顺序50群众三个高纬度云对激波阵面
中号
⊙
。云朵的“头部”带有延伸的“尾巴”，高分辨率图像显示“头部”的前缘上的弧形可能是个别的冲击。由于冲击加速材料，H
i
在前缘显示出较高速度的气体。对于两对云，一个云具有活动的震荡，表示为宽H
i
和偏移H
i
，而另一云已被震撼，并且主要是“ CO暗” H
2。
。二维MHD模拟平行于成对的云对与磁场的冲击，显示出与观察到的云特征有显着相似性，包括由于对齐的流和磁场而合并的“尾巴”，这导致了下游的横向约束。磁场和气流之间的平行排列可能导致形成小分子云。
The diffuse interstellar medium (ISM) is dynamic, and its chemistry and evolution are determined by shock fronts as well as photodissociation. Shocks are implied by the supersonic motions and velocity dispersion, often statistically called “turbulence”. We compare models of magnetohydrodynamic (MHD) shocks, with speeds typical of cloud motions through the ISM (3–25 km s
−1
) and densities typical of cold neutral gas (∼10
2
cm
−3
), to archival observations of the H
i
21 cm line for gas kinematics, far-infrared emission for dust mass, and mid-infrared emission for high-resolution morphology, to identify shock fronts in three high-latitude cloud pairs with masses of order 50
M
⊙
. The clouds have “heads” with extended “tails,” and high-resolution images show arcs on the leading edges of the “heads” that could be individual shocks. The H
i
shows higher-velocity gas at the leading edges due to shock-accelerated material. For two cloud pairs, one cloud has an active shock indicated by broad and offset H
i
, while the other cloud has already been shocked and is predominantly “CO-dark” H
2
. Two-dimensional MHD simulations for shocks parallel to the magnetic field for pairs of clouds show a remarkable similarity to observed cloud features, including merged “tails” due to aligned flow and magnetic field, which leads to lateral confinement downstream. A parallel alignment between magnetic field and gas flow may lead to formation of small molecular clouds.
