This project is funded by the European Research Council through a 2011 Starting Grant (PI E. Khomenko).

The broad scientific aims of the SPIA project is to better understand the magnetism of the Sun and to establish connections between the magnetic activity in sub-surface layers and its manifestation in the outer atmosphere.

Being the closest star, the Sun is the only one whose surface can be spatially resolved. Solar astronomers are lucky to obtain information about their object of research at spatial and temporal resolutions impossible in other fields of astrophysics. The state-of-art techniques in modern observational solar physics make it possible to reach a spatial resolution of 0.1 arc seconds, meaning that we can “see” details on the Sun as small as 70 km (the size of the island of Tenerife). To increase our understanding, the models describing the physical processes are forced to be one step ahead in their degree of realism over the field of stellar astrophysics. This makes the Sun a threshold star. Many stars are similar to the Sun in their magnetic activity cycles, presence of starspots on their surface, or active phenomena such as jets. Understanding the magnetic activity of the Sun can be extended to other stars, guiding theories of stellar structure and evolution.

The complex interactions in magnetized stellar plasmas are best studied via numerical simulations, a new powerful method of research that appeared in astrophysics with the development of large supercomputer facilities.

With a coming era of large aperture solar telescopes, ATST and EST, spectropolarimetric observations of the Sun will become available at extraordinary high spatial and temporal resolutions. New modelling tools are required to understand the dynamical behaviour of the plasma, related to magnetic field, at these tiny spatial scales. The aim of this project is to create such tools.

The SPIA project is exploring a novel promising approach for the description solar atmospheric plasma under multi-fluid approximation.

The degree of plasma ionization in the photosphere and chromosphere of the Sun is extremely low and significant deviations from the classical magneto-hydrodynamic description are expected. We are working on implementation of a multi-fluid plasma description, appropriate for a partially ionized medium, relaxing approximations of classical magneto-hydrodynamics. The SPIA reseach group is developing a three-dimensional multi-fluid numerical code with a goal to perform simulations of solar sub-photospheric and photospheric regions, up to the low chromosphere, with a realism not achieved before.