Physics-based Modelling of the Radiation Belts

Earth’s radiation belts consist of highly energetic protons and electrons trapped by Earth’s magnetic field in the region of 1.2~8 Re (Earth radii) away from Earth’s center. Highly energetic protons mainly distribute in the inner radiation belt, which typically locates 1.2~2.5 Re away from geocenter. The inner radiation belt is relatively stable, while the outer radiation belt is highly dynamic, which exhibits dramatic variability over timescales from minutes to hours. The inner and outer belts are separated by a slot region at around 2~3 Re where energetic particle flux levels are usually low. Highly energetic electrons in the Earth’s radiation belts are hazardous for satellite equipment.

To understand the dynamic evolution of outer radiation belt, physics-based 3D and 4D Versatile Electron Radiation Belt (VERB) codes are developed by our group. Important mechanisms controlling the dynamic evolution of radiation belts involve radial diffusion, local acceleration, local loss, magnetopause shadowing and electric convection. There are various plasma waves in the inner magnetosphere, such as whistler mode chorus waves, hiss waves, electromagnetic ion cyclotron (EMIC) waves and ULF waves. Wave-particle interactions play an important role in the processes of radial diffusion, local acceleration and local losses. To quantify wave-particle interactions between various types of waves and energetic electrons, bounce-averaged diffusion coefficients are calculated using our Full Diffusion Code (FDC). Then these diffusion coefficient can be utilized in the VERB code to solve the Fokker-Planck equation, which is capable of computing the 1D, 2D, 3D and 4D evolution of the Phase Space Density (PSD) of energetic electrons, as shown in Figure below.

Comparison of electron PSD modeled by the VERB code simulations with a multisatellite PSD reanalysis.
Comparison of electron PSD modeled by the VERB code simulations with a multisatellite PSD reanalysis.

The upper image shows the comparison of electron PSD modeled by the VERB code simulations with a multisatellite PSD reanalysis at µ=700MeV/G and K=0.11G0.5RE [Shprits et al., 2011]. From top to bottom: (a) Kp index; (b) multisatellite PSD reanalysis, dashed red and green lines indicate the beginnings of the main and recovery phase of storms; (c) flux variation used at the outer radial boundary of the code, obtained from the CRERES measurement; (d) the radial diffusion only model with losses parameterized as 5/Kp days outside of the plasmasphere and 5 days inside of the plasmasphere; (e) radial and pitch angle diffusion model; (f) 3-D radial, energy, and pitch angle diffusion; (g) 3-D simulation with mixed terms. The white curves show the calculated location of the plasmapause Lpp. [Subbotin et al., 2011].


Profile photo of  Prof. Dr. Yuri Shprits

Prof. Dr. Yuri Shprits
Magnetospheric Physics

Behlertstraße 3a
Building K 3, room 012
14467 Potsdam
tel. +49 331 288-28899