NEWS & PRESS
The largest disturbances to the Earth's geomagnetic environment occur when it is buffeted by solar material hurled in our direction by explosive changes in the Sun's atmosphere. These Coronal Mass Ejections or CMEs contain approximately a billion tonnes of ionized gas or plasma and can have a dramatic and damaging impact on everything from satellites to power grids.
Now a team of scientists have used two spacecraft to study these events in unprecedented detail. Graduate student Anthony Williams of the University of Leicester will present their results on Tuesday 19 April at the Royal Astronomical Society’s National Astronomy Meeting in Llandudno, Wales.
Mr Williams and his team used the Heliospheric Imagers (HI) on the Solar TErrestrial RElations Observatory (STEREO) spacecraft to examine the internal structure of an Earth-impacting CME – seen as sunlight scattered from high density blobs of plasma – as it travels outwards from the Sun. They compared this with the internal structure measured in situ by the Advanced Composition Explorer (ACE) spacecraft as the CME engulfed the spacecraft and impacted the Earth. This meant that the scientists have for the first time been able to compare the evolution of the CME structure as it races towards the Earth and the internal structure observed as it arrives.
The CME studied was ejected from the Sun on 19 March 2010, when the STEREO A spacecraft was in a position to watch from the side as the CME hurtled outwards towards the Earth. The structure of the CME was examined in HI images spanning a distance of approximately 48 million km at different distances between the Sun and the Earth. Analysing the images indicated that its speed was close to 350 km per second, which allowed its time of impact on the Earth to be predicted some 3 days after the initial ejection.
The results indicate that the CME structure evolves considerably on its outward journey, and that the internal structure can be difficult to predict from the images. And there is another key facet to this work – imaging CMEs with spacecraft like STEREO is an extremely effective means of forecasting their impact on Earth and the large scale disruption that can sometimes result.
Anthony Williams (at NAM2011 Monday and Tuesday)
NAM 2011 Press Office (0900 – 1730 BST, 18-21 April only)
Dr Robert Massey
Images and movies
Images and movies of the CME can be downloaded from ftp://www.ion.le.ac.uk/pub/aow2/
The following four images chart the progress of the CME as it travelled from the Sun towards the Earth on 19 and 20 March 2010. All four are visible light images made with the HI instrument on STEREO. The x-axis of each image corresponds to a distance of 48 million km from left to right. Credit: Anthony Williams / NASA / Richard Harrison
Images of the same event have been assembled into a movie that can be seen at ftp://www.ion.le.ac.uk/pub/aow2/19-23_mar_2010_A_HI1.wmv
Notes for editors
Bringing together around 500 astronomers and space scientists, the RAS National Astronomy Meeting 2011 (NAM 2011: http://www.ras.org.uk/nam-2011) will take place from 17-21 April in Venue Cymru (http://www.venuecymru.co.uk), Llandudno, Wales. The conference is held in conjunction with the UK Solar Physics (UKSP: http://www.uksolphys.org) and Magnetosphere Ionosphere and Solar-Terrestrial Physics (MIST: http://www.mist.ac.uk) meetings. NAM 2011 is principally sponsored by the RAS and the Science and Technology Facilities Council (STFC: http://www.stfc.ac.uk).
The Royal Astronomical Society
The Royal Astronomical Society (RAS: http://www.ras.org.uk), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 3500 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.
The Science and Technology Facilities Council
The Science and Technology Facilities Council (STFC: http://www.stfc.ac.uk) ensures the UK retains its leading place on the world stage by delivering world-class science; accessing and hosting international facilities; developing innovative technologies; and increasing the socio-economic impact of its research through effective knowledge exchange. The Council has a broad science portfolio including Astronomy, Particle Astrophysics and Space Science. In the area of astronomy it funds the UK membership of international bodies such as the European Southern Observatory.
Venue Cymru (http://www.venuecymru.co.uk) is a purpose built conference centre and theatre with modern facilities for up to 2000 delegates. Located on the Llandudno promenade with stunning sea and mountain views; Venue Cymru comprises a stunning location, outstanding quality and exceptional value: the perfect conference package.