So, while we expect a storm to occur in November of 1998, there is historical precedent for a storm to also occur in November of 1999. The encounter with the debris cloud from Temple-Tuttle will last several days, but the most intense part of the encounter, the storm, typically lasts only 2 to 3 hours. All spacecraft in orbit around the Earth will be hit. Even spacecraft in low-Earth orbit will be shielded by the Earth only for part of the storm. The particles from a cometary debris cloud are typically very small, smaller than the diameter of a human hair, and tend to burn up at very high altitudes.
None reach the surface of the Earth.
Hence, there is no danger to the Earth s surface or to aircraft. In space, however, we have a different story. The result is that even a grain of sand the size of the head of a pin has the same energy as a .22 caliber bullet. At these speeds, the impact of a particle smaller than the diameter of a human hair can create an electrically charged cloud, a plasma, to form. This plasma can cause a sudden electrical pulse which can upset sensitive electronics.