Dynamics of Complex Magnetic Fields: From the corona to the solar wind

This project, entitled "Dynamics of Complex Magnetic Fields: From the corona to the solar wind'', is a continuation of a successful collaboration between the researchers of the Universities of Dundee and Durham on the entangled nature of magnetic fields in the solar atmosphere. The corona, the outer atmosphere of the Sun, is a dynamic plasma permeated by a magnetic field. This magnetic field is responsible for creating long-lived structures such as coronal loops, for heating the corona to its multi-million degree temperatures, and for explosive events such as solar flares and coronal mass ejections. These powerful explosions lead to major space weather events at Earth, creating the Northern and Southern lights but also having the potential for damaging economic impacts on engineered systems, ranging from satellites and communication systems to power grids and pipelines. It is becoming apparent that forecasting the occurrence and impact of space weather events cannot rely on static extrapolation models but requires a deep understanding of the dynamical behaviour of the Sun's magnetic field. Details of the complex, three-dimensional magnetic fields in the Sun's corona are a critical part of the space weather chain of events. At the same time, it is important to understand the manner in which these magnetic structures evolve in the solar wind as they are carried out towards Earth. This consortium aims to address these questions, as part of a wider goal in the scientific community of understanding the formation of structures in astrophysical plasmas.

Different projects within the consortium will focus on different aspects of the chain of events. We will address problems such as: How can we best model the build-up of coronal magnetic structure over time? What is the nature of the twisted magnetic "flux ropes" that form in the corona, and how does their structure evolve as they erupt and form coronal mass ejections? Where is the source of the non-steady slow component of the solar wind? What is the mechanism that makes the Sun's corona so hot? What controls the lowest energy state to which the coronal magnetic field can relax, and therefore how much energy is available to heat the plasma? Can we predict the equilibrium structure of the corresponding relaxed states? Common to each of these questions is the challenge of understanding dynamical, multi-scale processes in the Sun's coronal magnetic field.

We will use a combination of numerical simulations and mathematical modelling to tackle these questions, primarily using the non-linear partial differential equations of magnetohydrodynamics. Importantly, the modelling will take input from the latest generation of solar telescopes - several of our models will be directly "data-driven", and observations will be used to validate output (from global simulations of the coronal magnetic field to predictions of the slow solar wind and structure of magnetic clouds at Earth). Combined, the results will help to predict and explain events in the solar corona and to answer STFC's Science Roadmap Challenge B:2 ("How does the Sun influence the environment of the Earth and the rest of the Solar System?"), as well as to understand some of the basic plasma physical processes that go on throughout the Universe.

Eruptive magnetic storms on the Sun (Coronal Mass Ejections) regularly reach the Earth's space environment. The economic consequences of this space weather can be severe, and include damage to satellites and power grids, corrosion of oil and gas pipelines and disruption of communication systems. Furthermore, these events may endanger the health of astronauts and those onboard high-flying aircraft. The proposed research seeks to develop an understanding of how complex magnetic structures in the Sun's atmosphere change and interact, with these interactions being a critical part of the chain of events that generates solar eruptions. As such, a possible major impact of the proposed research will be on the international effort to develop reliable space-weather forecasting systems. (Given notice, defensive measures can be taken against the aforementioned effects.)

Project 1.1, examining the dynamics of the global solar corona, will allow for significantly improved simulations of the Sun's magnetic field on global scales. This will have potential impacts both on short-term space weather forecasting and on reconstructions of the Sun's magnetic field in the past which, in turn, will affect reconstructions of the Earth's climate in the past. Similarly Projects 1.2 and 1.3, on the slow solar wind and the structure of magnetic flux ropes ejected from the Sun, will both help to improve our knowledge of the space weather in proximity of the Earth.

Projects 1.4 and 1.5 investigate the dynamics and structure of complex magnetic fields, a fundamental problem of astrophysical and laboratory plasmas (e.g., in controlled thermonuclear fusion). This research in particular - and the other projects to a lesser extent - should be seen in the wider framework of the analysis of complex multi-scale systems which we encounter in many areas of science: the weather, cellular networks, material sciences, neurosciences, nuclear sciences, etc. The theoretical tools and methods created for investigating astrophysical plasmas have both benefited from and contributed to progress in these areas, via exchanges of ideas, software and human resources.

More generally, astronomy has a strong cultural impact. Due to the Sun's close proximity and the stunning images being gathered by new satellites, solar physics has a great capacity to get young people interested in science, contributing to UK's skilled labour market. We will engage with schools and the general public on our research findings through the Schools Outreach Programme of the Division of Mathematics in Dundee, via press releases, articles in popular science magazines and public events such as the Dundee Science Festival. These methods are further documented in the Outreach section of the Impact Plan document.