FIGURE 3.2 A diagram of the Van Allen radiation zone surrounding Earth. This cutaway image shows the weak inner zone, the “slot” region that is relatively devoid of trapped radiation, and the more intense and highly variable outer Van Allen belt. The two spacecraft of the Radiation Belt Storm Probes mission are shown schematically. SOURCE: Courtesy of NASA.


and at their most destructive they damage electronics components, including the temporary (single-event) upset of spacecraft commanding. Furthermore, upper atmospheric heating associated with the dynamics of the space environment can dramatically change drag effects on low-Earth-orbiting satellites, notably the International Space Station (ISS).

Ionospheric Variability, Communication, and Navigation

The specification and forecasting of ionospheric scintillation (i.e., radio propagation fluctuations due to plasma density irregularities) is a high priority for both civilian and military space operations. These scintillations are prevalent at low geographic latitudes as well as in the auroral regions, disrupting radio communications in critical geographical locations. They occur more frequently and extend to higher altitudes during times of high solar activity. Changes in ionospheric total electron content during geomagnetic storms compromise the performance of GPS technology vital for aviation and many other commercial and defense applications (see Figure 3.3). The participating electrons from the aurora also charge space systems, such as the ISS, generating the danger of arcing associated with discharges.

Radiation and Human Space Exploration

Humans venturing into space are vulnerable to damage caused by episodic radiation in the form of energetic particles from the Sun and from cosmic rays that constantly impinge on the solar system from

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