1. Introduction

2. The Earth's trapped radiation environment

4. Shortcomings of present day radiation belt models

References

3. Effects of trapped radiation on spacecraft and components

Due to their large energy coverage, trapped particles cause a variety of effects in spacecraft, components and biological systems.

Low energy electrons contribute to spacecraft surface charging. High energy electrons injected and accelerated through the magnetotail can cause dielectric charge buildup deep inside geosynchronous spacecraft which may lead in turn to destructive arcing. Inner and outer belt electrons also contribute to ionising doses through direct energy deposition and bremsstrahlung effects.

High energy protons in the inner radiation belt are the main contributors to ionising dose deposition in shielded components. They also dominate Single Event Upset (SEU) rates at low altitudes and latitudes, where cosmic rays and solar energetic particles are effectively shielded by the geomagnetic field. Lower energy protons (up to 10 MeV) contribute to Non-Ionising Energy Loss (NIEL) dose which affects Charged-Coupled Devices (CCD) and other detectors; unshielded detectors can be affected even in the outer belt, where <1 MeV protons are present.

The ionising dose contributions of trapped protons and electrons are illustrated in figure 9, which shows dose in Si (calculated with the SHIELDOSE code (14)) as a function of shielding thickness accumulated over an 800 km heliosynchronous orbit.

Figure 9. Ionising doses in Si as a function of Al shielding thickness for an 800 km heliosynchronous orbit.

Doses induced by solar flare protons (obtained with the JPL-91 model (15)) are shown as well. Electron doses dominate for thin shieldings, while trapped and solar flare proton doses become more important for thicker shielding. It should be noted that for this orbit trapped proton doses are higher than solar flare proton doses except for the lowest shielding thicknesses.