Planetary space simulations based on the particle description for electrons and ions.

The question about how solar storms impact a planet has both fundamental scientific importance and great

social impacts for protecting our infrastructure from the most powerful solar storms. At present, models rely

on a fluid description of the electrons due to algorithmic and computational challenges. Our goal is to develop

a model of the space environment around a planet based on a particle description of both ions and electrons.

We plan to use the particle in cell (PIC) model where both ions and electrons retain their nature as particles.

This PIC model will allow us to investigate the critical role of energetic electrons participating in the energy

and matter transfer from the solar wind to the planet inner space.

What makes this goal now possible is the Energy Conserving semi implicit method (ECsim), developed by

the PI. The ECsim conserves energy exactly, a critical element in the investigation of energy flow from the

solar wind. In addition, the energy conservation leads to enhanced numerical stability, which in turn greatly

augment ECsim’s capability to simulate very large systems such as planet atmospheres while treating electrons

as particles rather than fluid. We will start from this new development and introduce two critical innovations.

First, we will implement adaptive spatial and temporal resolution for finer resolution closer to the planet and

in selected areas of interest. Second, we will implement CPU-GPU algorithms for the new heterogeneous

supercomputers developed by EuroHPC.

These innovations will increase the capability of ECsim by more than an order of magnitude making it possible

to model a region as big as the Earth space environment with the computers available within the next 3-5 years.

If successful, we will have the first PIC model to describe a planetary space environment where the correct

particle nature of the electrons is considered with all its implication for the energy and matter transport.