al review articles on the subject were also published as part of the recent Special Issue on Single Event Effects and the Space Radiation Environment in the IEEE Transactions on Nuclear Science [3-8]. The intent is not to repeat a great deal of this information here, but rather to give a brief overview of some of the more important points that may be of use later as SEE mechanisms are discussed. The reader is directed to the above references for more details on the space radiation environment. Trapped Particles Charged particles that come into contact with the Earth's magnetic field can become trapped in the near-Earth environment. These particles include electrons, protons, and heavy ions. Electrons are very important components of the space environment because they inflict damage on spacecraft through total ionizing radiation dose and spacecraft charging effects [9-11]. Because electrons do not usually contribute to single-event effects, we will limit our discussions to trapped proton and heavy ion populations. The trapped particle belts (Van Allen belts) consist of two regions of trapped particles: an inner belt centered at about 1.5 Earth radii, and an outer belt of particles at about 5 Earth radii, separated by a region of reduced (but non-zero) particle flux (the so-called "slot" region). References [1] and [2] contain helpful illustrations of the belt structure around the Earth. Although the origin of trapped particles in the near-Earth environment is not completely understood [1], sources include the solar wind and transient solar events, cosmic ray particles from interplanetary space, and reaction products from cosmic ray collisions with the Earth's atmosphere. It was recently discovered that transient solar events can actually produce new trapped particle belts of surprisingly long duration [4,6]. 2.1.1 Protons Regardless of origin, energetic protons do exist in the near-Earth environment and are one of the most prominent sources of SEE. They range in energy from tens of keV to hundreds of MeV, with flu