ROYAL ASTRONOMICAL SOCIETY PRESS INFORMATION NOTE
Ref.: PN 08/24 (NAM 15)
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Dr Robert Massey
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E-mail: rm(at)ras.org.uk
NATIONAL ASTRONOMY MEETING PRESS ROOM (31 MARCH - 4 APRIL ONLY):
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NAM 2008 website:
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CONTACT DETAILS ARE LISTED AT THE END OF THIS RELEASE.
STEREO SNAPS FIRST FOOTAGE OF A SOLAR TSUNAMI
Images from the twin STEREO spacecraft show, for the first time, a solar
tsunami blasting its way through the Sun?s lower atmosphere. The discovery
will be presented by David Long at the RAS National Astronomy Meeting in
Belfast on Wednesday 2nd April.
Solar tsunamis are launched by huge explosions near the Sun's atmosphere,
called coronal mass ejections (CMEs). Although solar tsunamis share much in
common with tsunamis on Earth, the solar version can travel at over a
million kilometres per hour.
The tsunami took place on 19th May 2007 and lasted for about 35 minutes,
reaching peak speeds around 20 minutes after the initial blast. The
observations were made by a team from Trinity College Dublin.
"The energy released in these explosions is phenomenal, about two billion
times the annual world energy consumption in just a fraction of a second. In
half an hour, we saw the tsunami cover almost the full disc of the Sun,
nearly a million kilometres away from the epicentre," said Long.
STEREO's Extreme Ultraviolet Imager (EUVI) instruments monitor the Sun at
four wavelengths which correspond to temperatures ranging between 60 000 and
2 million degrees Celsius. At the lowest of these temperatures, scientists
can see structures in the chromosphere, a thin layer of the solar atmosphere
that lies just above the Sun's visible surface. At temperatures between 1
and 2 million degrees Celsius, scientist can monitor features at varying
levels in the solar corona.
The SOHO spacecraft, which was launched in 1995, also monitors the Sun at
these wavelengths but only took images four times per day, giving scientists
rare snapshots of these tsunamis. STEREO's EUVI instruments take an image
every few minutes to create a series, making it possible for scientists to
track how the wave spreads over time.
This is the first time that a tsunami has been observed at all four
wavelengths, which enabled the team to see how the wave moved through the
different layers of the solar atmosphere.
"To our surprise, the tsunami seems to move with similar speed and
acceleration through all the layers. As the chromosphere is much denser
than the corona, we'd expect the pulse there to drag. It's a real puzzle,"
said Dr Peter Gallagher.
To complicate matters, the interval between images is not the same for all
four cameras. At the time of the tsunami, the cameras monitoring radiation
at 1 million degrees Celsius were set to take an image every 2.5 minutes.
They recorded much higher speeds and accelerations for the wave than the
other cameras, which were on 10 or 20 minute cycles. By taking a sample of
one image in four, the data from these cameras matched the lower values
observed in the other layers.
"We've thought for some time that the tsunamis might be caused by magnetic
shockwaves but, in previous snapshots, the waves appeared to be travelling
too slowly. However, we've seen from this set of observations that if the
time interval between images is too long, it's easy to underestimate the
speed that the waves are moving. With a few more rapid-sequence
observations of solar tsunamis, we should finally be able to identify the
cause of these waves," said Gallagher.
IMAGES
Images and animations showing the solar tsunami can be found at:
http://www.physics.tcd.ie/Astrophysics/tsunami
NOTES FOR EDITORS
RAS NATIONAL ASTRONOMY MEETING
The RAS National Astronomy Meeting (NAM 2008) is hosted by Queen's
University Belfast. It is principally sponsored by the RAS and the STFC. NAM
2008 is being held together with the UK Solar Physics (UKSP) and
Magnetosphere, Ionosphere and Solar-Terrestrial (MIST) spring meetings. For
details, see: http://nam2008.qub.ac.uk
STEREO
The Solar TErrestrial RElations Orbiter (STEREO) is a NASA-led mission, with
major contributions from European countries including the UK. The mission
consists of two space-based observatories, one ahead of Earth in its orbit
and the other trailing behind.
For further information, see:
http://stereo.gsfc.nasa.gov
http://www.solarmonitor.org/index.php
CONTACTS
Dr Peter Gallagher
Lecturer in Astrophysics
Astrophysics Research Group
School of Physics
Trinity College Dublin
Dublin 2
Ireland
Tel: +353 (0)1 896 1300
Fax: +353 (0)1 671 1759
E-mail: peter.gallagher(at)tcd.ie
On Tuesday 1st April and Wednesday 2nd April, Dr Gallagher can be contacted
through the NAM press office (see top of release for details)
David Long
PhD student
Astrophysics Research Group
School of Physics
Trinity College Dublin
Dublin 2
Ireland
Tel: +353 (0)1 896 1300
Fax: +353 (0)1 671 1759
E-mail: dlong(at)tcd.ie
On Tuesday 1st April and Wednesday 2nd April, Mr Long can be contacted
through the NAM press office (see top of release for details)
Dr. James McAteer
Marie Curie Fellow
Astrophysics Research Group
School of Physics
Trinity College Dublin
Dublin 2
Ireland
E-mail: rtjmca(at)gmail.com
From Monday 31st March to Friday 4th April, Dr McAteer can be contacted
through the NAM press office (see top of release for details)
Dr. Shaun Bloomfield
Postdoctoral Fellow
Astrophysics Research Group
School of Physics
Trinity College Dublin
Dublin 2
Ireland
E-mail: shaun.bloomfield(at)tcd.ie
From Monday 31st March to Friday 4th April, Dr Bloomfield can be contacted
through the NAM press office (see top of release for details)
