A ray of sunshine with Lucie Green
26 May 2011 by Evoluted New Media
They travel at 2000km/s and could well be heading our way - who better to chat to about coronal mass ejections than all round solar expert and sole female presenter on Sky at Night - Dr Lucie Green
Dr Lucie Green is a solar researcher based at the Mullard Space Science Laboratory, UCL's Department of Space and Climate Physics where she studies activity in the atmosphere of our nearest star, the Sun. In particular she is interested in understanding how the Sun ejects huge clouds of magnetic field and hot gases into the solar system. Lucie holds a Leverhulme Fellowship and as well as her solar physics research also works in TV and radio – including being the only female presenter on Sky at Night.
Why should we be studying the sun?
The reasons for studying the Sun are two-fold. First, we have a unique opportunity to closely study fundamental physical processes which control how a star lives. We can spatially resolve features on the Sun's visible surface and in the atmosphere. With this abundant information have come advances in science with far reaching consequences. For example, solar spectroscopy and atomic physics developments have transformed astrophysics, in particular, in X-ray studies of supernovae and galaxy clusters. Currently, the models of magnetic field topologies associated to solar activity are being applied to other astrophysical systems. Secondly, the Sun has such a major impact on the Earth's atmosphere and magnetic field, and therefore on our lives – many of the Sun's effects go unnoticed but some, such as the Northern Lights, are enjoyed by many. Now is a particularly good time to be studying the Sun as its activity is picking up and is expected to peak around 2013.
What are coronal mass ejections and do they pose any danger to the Earth?
Coronal mass ejections (CMEs) are eruptions of magnetic field from the solar atmosphere that carry magnetic flux and charged particles into the Solar System. They are vast structures which can move with speeds of up to around 2000 km/s. The frequency of CMEs varies over an 11 year activity cycle. There is maybe one per day at activity minimum and five a day at maximum. CMEs can be launched in any direction and this includes toward the Earth!
Many CMEs will wash over the Earth, with the CME having no major effect on us. However, some have a magnetic configuration, velocity and mass which result in the CME having a very major effect on our magnetic field and particle environment. Having the correct magnetic configuration is important because it allows the energy carried by the CME to flow into the Earth's magnetosphere through a process known as magnetic reconnection. A series of physical process can then take place which ultimately induce currents on transmission lines and pipelines, cause expansion of the upper thermosphere leading to enhanced drag on low orbiting satellites and, in the worst- case scenario, even totally disable spacecraft as a result of electrical discharge (e.g. the Telstar 401 and Anik spacecraft in the 1990s).
How can you tell so much about the sun given the distances involved?
The Sun is such an extremely important object for us here on Earth and because of this there is a fleet of international spacecraft monitoring it 24/7. I work with a Japanese spacecraft called Hinode on which there is a UCL-led telescope. Using the light given off by the Sun we can use our telescope to study the composition, temperature and flows in the atmospheric gases.
Other telescopes are able to measure the fingerprint of the Sun's magnetic field allowing us to learn how the magnetic structures in the Sun's atmosphere evolve, including the build up and release of magnetic energy. In addition, we can directly place our spacecraft in the Sun's emissions of plasma and magnetic field. The ESA/NASA mission called SOHO has been making such measurements from the 1st Lagrange point since its launch in 1995.
You’re based at MSSL at UCL – tell us what you do there.
I am a Leverhulme Research Fellow working in the solar physics group. I study immense magnetic fields in the Sun's atmosphere which sporadically erupt to form a coronal mass ejection. My main interests lie in the exact structure of these magnetic fields and the forces which act. Understanding both these aspects is allowing us to develop a model which describes the driver and trigger for coronal mass ejections.
I am also very active in engaging the public with the research and engineering that we carry out at MSSL. I coordinate a wide programme of activities that aims to encourage a greater dialogue between us and various public groups such as school students, adult learners and family audiences.
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How did you get into solar astronomy?
I read Physics with Astrophysics at the University of Sussex and whilst there made a couple of trips to observe the Sun at the Crimean Astrophysical Observatory, close to the Black Sea. It was this solar observing that sparked my interest in solar physics. I discovered that the Sun isn't a bland and quiet object but rather it has an active and extended atmosphere which affects us. I hope to contribute to a complete understanding of the Sun's activity and push forward our knowledge of the mechanisms through which energy flows from the Sun to the Earth.
