The ground is cold and moist, with the chill factoramplified by ventilation fans used to blow fresh air into the mine, and the sprinkler that keep the coal dust down.
因为有通风设备往里面输送新鲜空气，还有洒水器不断地给煤浇水以降温，所以地下既阴冷又潮湿。
2
All this adds up to unexpectedly rapid cosmic-ray acceleration in a magnetic field amplified by a factor of more than 100.