UNDERSTANDING THE DYNAMICAL SOLAR ATMOSPHERE

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Within this proposal we aim to study various aspects related to dynamical processes that frequently occur in the solar atmosphere, and that are still not understood. Solar physics is now experiencing a golden age in terms of observations of the outer atmosphere of our star. In the past few years, a suite of space missions has been launched to observe the solar atmosphere in great detail.An upcoming mission, Solar Orbiter, is a major ESA satellite to be launched in 2018 and devoted to the study of the inner parts of the heliosphere, the bubble where our solar system resides that is constantly modified by events on the Sun. Some of these events have relevance to space weather, i.e. affect significantly the outer layers of the Earth atmosphere, causing significant effects on satellites, human space flight and communication, for example.Solar flares are massive releases of energy into the heliosphere in a short period of time. It is thought that magnetic reconnection is the main physical effect. We aim to measure, using current satellites, the observational signatures of the flare supra-arcade, a region where strong heating (to more than ten million degrees) occurs. We will investigate the physical processes at play in this region with large-scale 3-D numerical simulations. We will study how instabilities in the solar-flare reconnection region can produce supra-arcade downflows, and compare the results of the simulations with observations. We also aim to study the solar transition region, a thin layer of the atmosphere between the photosphere and corona of the Sun. This region is very dynamic, and we aim to study, with improvements in the models, if non-equilibrium effects can explain the strong emission that is coming from this layer and is observed by current missions. We will also study the importance of non-equilibrium effects in interpreting the observations of one of the Solar Orbiter instruments (SPICE), that will observe the solar transition region.We shall also study the dynamics of the high-temperature emission in solar active regions with a new-generation X-ray instrument, MaGIXS, which will be flown in 2018 on a sounding rocket. MaGIXS will provide novel measurements that will help us to understand which physical processes are responsible in heating the active region plasma to 3 million degrees, an issue that has been much debated over the past 40 years.We also aim to continue to provide the most fundamental atomic data for the interpretation of the observations of current and future solar missions. Our group has been leading this field by continuously updating the CHIANTI atomic database, now also widely used for astrophysical applications.Finally, we shall communicate our work to the public and to schools, in particular through the Sun|trek project.