Study of the terrestrial radiation belts (using PROBA-V/EPT and RBSP/MagEIS)

Details

Supervisors

Pierrard, Viviane

Faculty

Faculté des sciences

Degree label

Master [120] en sciences physiques, à finalité approfondie

Abstract

The Van Allen radiation belts were first discovered in the 1950’s with the launch of the first satellites. Since then, the need for satellites has become increasingly important for human activities. However, the radiative environment in which they evolve is a threat for all spacecraft as well as for astronauts. The radiation belts are toroidal regions filled with high energy particles, mainly electrons and protons trapped in the magnetic field of the Earth. The state of the belts is highly dependent on magnetic activity induced by the solar wind and processes involved in their dynamics are very complex. Radiation belts have been studied for decades now, allowing to improve our models and theoretical understanding of those regions. The intensive investigation of the radiation belts led to the need of instruments that are able to perform high resolution measurements, such as the NASA Magnetic Ion Electron Spectrometer (MagEIS) ondoard the Van Allen Probes or the ESA Energetic Particle Telescope (EPT), jointly developed by UCLouvain, BRIA- IASB and QinetiQ Space, carried by the PROBA-V satellite. Both instruments have provided (and still provides, in the case of the EPT) science data for several years. The main objective of this work is to perform a comparison of simultaneous obser- vations of the radiation belts from those instruments, despite the different orbit of the spacecraft. To this end, data from 2014 are used. A larger focus is brought on EPT mea- surements, which are used to characterize the main events that led to sharp variations in electron and proton populations during this year. Those observations are also compared to an empirical model of the belts based on previous averaged measurements. The comparison of the two instruments is carried out for the outer belt electron fluxes on two time intervals of three months. It is also performed at different locations in the belts, for various energy and the effect of the pitch angle for equatorial electrons is investigated. On the one hand, for the first data set, ranging from January to March, observations of the two instruments are well correlated especially for low pitch angle value equatorial electrons. On the other end, for data taken between October and December, the correlation of the two instruments is decreased and more particularly near the inner edge. This decrease is found to most likely be caused by a difference in geomagnetic activity between the two periods.