Simulating large scale solar magnetic fields: application to space weather

As our closest stellar neighbour the Sun plays a critical role in our daily lives, not only does it provide the light and energy required to sustain life on Earth, but it also affects us in much more subtle ways. Two phenomena on the Sun which can directly affect us are Coronal Mass Ejections (CMEs) and the Sun’s Open Magnetic Flux.

CMEs occur when a large amount of material is ejected from the Sun and are one of the most violent releases of energy within our solar system (Figure 1). They are particularly important when they are directed towards the Earth. They may damage or destroy satellites, short power grids and result in the loss of life for astronauts. Understanding the nature of CMEs and more importantly being able to predict them is of key importance with our reliance in modern communication systems. In addition we need to fully understand them before the solar system can be safely explored.

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Figure 1. Example of a Coronal Mass Ejection from the STEREO satellite (http://stereo.gsfc.nasa.gov/).

The Sun’s Open Flux is part of the Sun’s magnetic field that extends out from the Sun and into the Solar System. As the Earth orbits the Sun it travels through the Open Flux which continually interacts with the Earth’s magnetic field. The Open Flux shields us from high energy particles from outer space which can be dangerous to astronauts and satellites.

The overall research objective of this project is to conduct supercomputer simulations of solar magnetic fields to investigate the conditions that give rise to CMEs along with the variations in the Sun’s Open Flux. The research has four distinct objectives which will produce a complete picture of the nature of these phenomena.

  • Determine the origin of CMEs and derive statistics on their frequency distribution over the 11 year solar cycle;
  • Determine the origin and variation of Open Flux over the solar cycle;
  • Use computer simulations of the Sun’s global magnetic field (Figure 2) to predict locations of CMEs and the amount of open flux on a month by month basis from 2012-2015;
  • Study the effect and consequences of CMEs on the near Earth environment.

Dr Duncan Mackay
University of St Andrews

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Figure 2. Example of a global non-linear force-free field simulation for the Sun.

Duncan was awarded a Research Project Grant in November 2011; providing £116,863 over 36 months.