Search Results (2)

The exceptionally strong geomagnetic storm of 10–11 May 2024 injected new energetic protons and electrons into the terrestrial radiation belts, creating extraordinary conditions to study the loss mechanisms scattering these particles into the atmosphere after the storm. For the first time, four electron belts were observed during several weeks. We show that this structure was due to electron loss, highly dependent on specific positions. Using the proton and electron fluxes measured by the Energetic Particle Telescope, EPT, on board PROBA-V, we determine the lifetimes of these populations depending on their energy ranges and positions. We show that the lifetimes are much longer for protons than for electrons, which enables us to determine their time variations independently. For electrons, the wave–particle loss mechanisms depend on the background ionosphere–plasmasphere density. The lifetimes determined after the May 2024 and 10 October 2024 big events are compared with average ones to understand their unusual specificity for the formation of four and three belts, respectively. For the injected protons of 9.5 to 13 MeV, the lifetime is minimum at L~1.9, where the fluxes are maximum, showing a lifetime depending on the flux intensity. Loss is due to pitch angle diffusion and collisions with electrons and nuclei in the ambient plasma and neutral atmosphere. At the outer edge of the proton belt, the flux is depleted at all energies after the geomagnetic perturbation, and we determine that the progressive time of refilling after the storm generally reaches more than 40 days. There is an excellent discrimination between the different populations of energetic electrons (0.5–8 MeV) and the injected protons (9.5–13 MeV) that are still observed several months after the event. Such results contribute to advancing understanding of the interactions between the terrestrial atmosphere and space radiation. Full article

Plasma content and distribution are key parameters in the dynamics of the inner magnetosphere. The plasmasphere contributes, for the most part, to the plasma mass density, and its properties are very dependent on the history of the magnetosphere and geomagnetic activity. In this work, we investigated plasmasphere dynamics and plasmasphere–ionosphere coupling, focusing on the refilling process that followed the geomagnetic storm that occurred on 1 June 2013. The equatorial plasma mass density used to evaluate the refilling rates was remotely sensed by observation of the field line resonance (FLR) frequencies of the geomagnetic field, driven by ultra-low-frequency magnetic waves. The FLR frequencies were retrieved by performing an analysis of signals detected by several station pairs of the European quasi-Meridional Magnetometer Array. We estimated the rate at which the refilling process occurred, concentrating on both the diurnal and the day-to-day refilling rates. The estimated contraction rate during the main phase of the storm was higher than $\sim 3.5$ $R_E{d}^{-1}$, while the average expansion rate was $\sim 0.4$ $R_E{d}^{-1}$. We investigated the radial dependence of the refilling rates, using a novel approach based on fit plasma mass density profiles, and we related their variation to the plasmasphere boundary layer and the zero-energy Alfvén boundary. We found evidence supporting the idea that flux tubes mapping in the region between these two boundaries experience an enhanced refilling process. Full article