Radiation dropouts investigation and understanding of the causes of electron flux decreases during geomagnetic storms

• Applicants: Professor Dr. Ferdinand Plaschke; Professor Yuri Shprits, Ph.D.
• Subject Area: Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography ; Geophysics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 547667751

The Earth’s Van Allen radiation belts are hazardous for satellites and humans in space. They constitute the first discovery of the space age, and they continue to be one of the most intriguing and not well understood phenomena in space sciences. The radiation belts often show dramatic dropouts, where electron fluxes drop by several orders of magnitude on time scales that are shorter than the orbital periods of the observing spacecraft. The accurate understanding of the loss processes is still incomplete, and an accurate quantification of the loss mechanisms is still missing. There are two potential mechanisms of loss: (1) electromagnetic ion cyclotron (EMIC) wave scattering of energetic particles, suggested by Thorne and Kennel (1971), and (2) outward radial diffusion, driven by the loss of particles to the magnetopause, proposed by Shprits et al. (2006). The overarching objective of this project is to understand the causes of dropouts of radiation belt electrons at different energies. In particular, we will answer the following focused science questions Q1-Q7: Q1: How are the EMIC waves distributed in magnetic local time (MLT), radial distance from Earth, frequency, and wave normal angle? Q2: What is the relationship between the occurrence of EMIC waves, the solar wind, and geomagnetic activity? Q3: How is the location of the magnetopause and its variability related to solar wind conditions and geomagnetic activity? Q4: Is the distance from the magnetopause a better proxy for EMIC wave parameterization than the solar wind dynamic pressure and L? Q5: What is the relative contribution of EMIC waves and the outward radial diffusion driven by particle loss to the magnetopause for the loss of electrons in the radiation belts? Q6: How does the relative contribution of the loss to the magnetopause and loss by EMIC waves change with electron energy? Q7: Does the model of the radiation belts agree with observations of pitch angle distributions and the evolution of electron fluxes and their radial profiles, or is there an additional missing loss mechanism? To answer these questions, we will develop models of EMIC waves and MP location and variability that will be included in the Versatile Electron Radiation Belt (VERB) code. Sensitivity experiments will allow us to quantify the effects of each of the two described above mechanisms on the dynamics of the radiation belts at different electron energies. The detailed validation of the code results will help us understand if there are additional missing physical mechanisms of loss that are needed to explain the differences between the VERB code results and observations.

• DFG Programme: Research Grants
• International Connection: Czech Republic
• Partner Organisation: Czech Science Foundation
• Cooperation Partner: Benjamin Grison, Ph.D.