The contribution of wave-particle interactions to electron loss and acceleration in the Earth’s radiation belts during geomagnetic storms
The Earth’s radiation belts are a hazardous environment that pose a risk to astronauts and spacecraft on orbit. Having been discovered in 1958, there is renewed interest on the part of scientists as the well-established theories describing the formation and structure of the radiation belts are unable to adequately explain their dynamic behavior during geomagnetic storms. There is also new commercial interest, particularly from space insurers who have suffered substantial losses over the last three years, and who now wish to evaluate all forms of risk affecting spacecraft on orbit. Here, we review how the radiation-belt particles can damage satellites on orbit, and discuss briefly the large sums of money that are at stake. We discuss the variability of the electron radiation belts, their relation to the solar wind as a driver, and review the case for electron acceleration inside the Earth’s magnetosphere. We outline the main theories for acceleration, and comment on where current theories break down or where they are inadequate. We present the case for electron loss and acceleration as a result of wave-particle interactions, mainly due to ELF and VLF waves. We identify several key questions that need to be addressed, and review progress over the last three years. We conclude by identifying major issues that need to be addressed in order to make substantial future progress.