For several decades solar scientists have been hard at work trying to
unravel the mysteries of the solar corona. Thanks to a medical x-ray
technique known as tomography, scientists are able resolve solar
activity in greater detail. By using a new way of processing images,
active regions now take on dimensions never foreseen of by computer
models.
Today Dr. Huw Morgan presented his results to the Royal Astronomical
Society National Meeting in Belfast. Using an adapted medical X-ray
technique, scientists have produced the first detailed map of the
structure of the Sun's outermost layer, the corona. The application
known as tomography uses a series of images taken from many different
angles to reconstruct a 3-dimensional map created from direct solar
observations.
"This is a breakthrough for scientists trying to understand the corona
and the solar wind. We've been attempting to apply tomography to the
solar corona for more than 30 years but it's proved very difficult and
very inaccurate until now. The new technique that I've developed is
only in its infancy but shows great potential for areas of research
like space weather," said Dr Morgan, of the University of Aberystwyth.
The process has not been as easy one, nor is it a new idea. Without
images of the coronal far sidem researchers were left with only half
the data. The near side produces its own difficulties as well, since
the outermost areas of the corona are more than a thousand times
fainter than the regions near the Sun. This factor introduces huge
potential errors to observations. Thanks to Dr. Morgan, his new way
of processing coronal images, called Qualitative Solar Rotational
Tomography (QSRT), eliminates the steep drop in brightness and
associated errors. With the help of SOHO's LASCO instrument, Dr.
Morgan applied the technique to a series of images taken as the Sun's
rotation brings the 'missing' areas into view. The result? Full
coronal maps that are at least 5 times more detailed than previous
tomographical studies of the Sun. And the future may hold far more.
Says Morgan:
"I've now produced maps of the corona over almost a whole cycle of
solar activity, so we can now see in unprecedented detail how
structures develop and evolve in three-dimensions. The maps have
produced some interesting results: for instance we've observed large
areas of dense structures when the Sun is most active that are not
predicted by current computer models. We've also found evidence that
inner regions of the corona rotate at different speeds."
According to the RAS press release, the technique is already being
used by scientists at the Institute of Maths and Physics at
Aberystwyth University to interpret their radio-wave observations of
the solar wind. Dr. Morgan, together with colleagues at the Institute
of Astronomy at the University of Hawaii, is also using the maps to
interpret ultraviolet observations of the corona. Says Dr. Morgan:
"These maps will also prove useful in the important field of space
weather. Explosions at the Sun travel through space and often hit the
Earth. These energetic magnetic clouds can disrupt communication,
power supplies and be a major health hazard for astronauts and airline
pilots. Understanding and predicting these storms is a major goal of
solar science. The ability to map the whole 3D structure of the corona
is a critical step towards achieving this goal."
