A New Cyclo‐Synchrotron Model for Lunar‐Based Observations of Earth's Radiation Belts

Abstract The energetic electrons trapped in the terrestrial radiation belts spontaneously emit radiation due to magnetic deflection. The observation of this radiation can offer insights into the space and energy distribution of the electrons, as well as their temporal variability. Given the energy range of the electrons in the Earth's radiation belts (0.1 keV to 10 MeV), the emission corresponds to cyclo‐synchrotron radiation, an intermediate radiation regime between the low‐energy cyclotron radiation and the extremely relativistic synchrotron emission. Terrestrial cyclo‐synchrotron radiation cannot be observed from Earth as it is emitted at frequencies below the ionospheric cutoff frequency ( f < 10 MHz). However, a lunar near‐side observation could provide real time measurements of the dynamics of the Earth radiation belts. In this study, we present the development of a full cyclo‐synchrotron model for the electron radiation belt emissions, building upon a preliminary synchrotron model. While previous simulations focused on >1 MeV electrons, our new model is able to simulate the radiation of >100 keV electrons which have much larger fluxes than MeV electrons. This new model accurately simulates the cyclo‐synchrotron radiation emitted by Earth's radiation belts as observed from the lunar surface, which would help the design of lunar‐based radio interferometers and would offer a new perspective on radiation belts research and monitoring.