The plasmasphere is the innermost region of the Earth’s magnetosphere filled with cold (low energy ~ 1-10 eV) and dense (10-104 electrons/cm-3) plasma particles trapped in the Earth’s magnetic field. The plasmasphere forms a toroidal region surrounding the Earth and corotates with it.
The plasmapause is the outer boundary of the plasmasphere and, beyond this limit, the plasmatrough region (very low electron density) strongly interacts with external electromagnetic waves. The plasmasphere is eroded during geomagnetic storms giving rise to structures like plasmaspheric plumes and channels, whereas the ionosphere (upper atmosphere) refills the plasmasphere during quiet times.
The BSPM model
The BSPM is a semi-empirical 3D kinetic model of the plasmasphere developed and continuously improved by the Solar Wind group of BIRA-IASB . Based on physical mechanisms for the plasmapause formation and for the trajectories of particles trapped in the Earth’s magnetic field, it provides the number density and the temperature of the electrons and protons inside and outside the plasmasphere, as well as the position of the plasmapause, as a function of the geomagnetic activity driven by the Kp index.
The model is coupled to the International Reference Ionosphere (IRI) model to determine the number density and temperatures of the particles between 60 and 600 km of altitude as boundary condition.
A previous version of the BSPM model is running in near-real-time at the SSA (Space Situational Awareness) site of ESA (European Space Agency) providing animations of the equatorial and meridian plasmasphere electron density and temperature.
A new version of BSPM that provides the electron density in the ionosphere, the plasmasphere and the plasmatrough, is now available at the Virtual Space Weather Modeling Center (VSWMC) through on-demand executions. Figure 1 illustrates results from both implementations.
The equations describing the plasmatrough region have been recently modified using new satellite data from the NASA Van Allen Probes (VAP) mission  in the framework of the European Union H2020 SafeSpace project. Figure 2 compares the plasmatrough obtained with the ancient and the new parametrizations. Reference  provides more details.
A new version of the BSPM, v.2021, containing these improvements is already available in the SafeSpace chain of models, and was used to calculate the effects of wave-particle interactions on the radiation belts. We will soon make BSPM available on a platform assembling most of the observations and models of plasmasphere, ionosphere and thermosphere in the framework of the H2020 PITHIA project (Plasmasphere, Ionosphere and Thermosphere Integrated research environment and Access services: a Network of Research Facilities).
- Pierrard, V., Botek, E., and Darrouzet, F. (2021). Improving Predictions of the 3D Dynamic Model of the Plasmasphere. Frontiers in Astronomy and Space Sciences, 8:681401, https://doi.org/10.3389/fspas.2021.681401.
- Botek, E., Pierrard, V. and Darrouzet, F. (2021). Assessment of the Earth’s cold plasmatrough modeling by using Van Allen Probes/EMFISIS and Arase/PWE electron density data. Journal of Geophysical Research: Space Physics, 126(12), e2021JA029737, https://doi.org/10.1029/2021JA029737.