The University of
Hawaii Institute for Astronomy (IfA) has conducted thorough research on the
solar corona – the outermost atmospheric layer of the sun that expands into
interplanetary space. The basic properties of the solar corona are directly
visible due to the Sun’s complex magnetic field that is not only produced in
the solar interior but also extends widely throughout the solar system.
A student investigated
the shape of the coronal magnetic field with a higher spatial resolution by using
the observations of the entire solar eclipse. The area covered was larger than
ever and the results were outstanding. The results were published on June 3rd
in the Astrophysical Journal.
You can view the corona
quite distinctly during a total solar eclipse – when the moon blocks the
sunlight entirely by coming in between the Earth and Sun. Distinguished
technical advancements in recent years have transformed the majority of
analysis into space-based observations. This involves the wavelength of light
that isn’t accessible from the ground. Although you can get a picture throughout the
year, at any point and time, there are certain aspects of the studies that can
only be investigated during a total solar eclipse.
The graduate student
was supervised by UK Manoa Astronomy Professor Shadia Habbal – also a coronal
research expert for over 20 years. These observations have made massive
breakthroughs and unraveled some of the secrets of the physical process that
not only define the corona but also the universe itself.
corona has been observed with total solar eclipses for well over a century, but
never before had eclipse images been used to quantify its magnetic field
structure. I knew it would be possible to extract a lot more information by
applying modern image processing techniques to solar eclipse data.”
– Said Boe, the graduate student/researcher.
Boe used the automatic
tracing method to trace the pattern of the magnetic field lines in the corona
that were widely distributed. The data was significant as it provided an
opportunity to study the constantly evolving changes in the corona over the
two 11-year magnetic cycles of the Sun.
fine-scale structures all over the corona. In fact, when the high-resolution
images were studied, he found that even smaller scales existed implying that
corona is even more structured and explicit that it was previously understood.
To further elaborate these changes, he calculated the magnetic field angle that
is relative to the surface of the Sun.
Furthermore, when the
solar activity is at a minimum, the corona’s field emanates right out of the Sun
closer to the equator and the poles. It usually comes out from different angles
at the mid-latitudes. However, when the activity level is maximized, the
coronal magnetic field is less organized and more radial.
explains: “We knew there would be
changes over the solar cycle but we never expected how extended and structured
the coronal field would be. Future models will have to explain these features
in order to fully understand the coronal magnetic field.”
The conceived results give
the impression that the coronal magnetic field is radial beyond the previously
assumed 2.5 solar radii. On the contrary, the current study reveals that the
coronal field is often non-radial to at least 4 solar radii.
also benefit the formation of solar winds that directly impact the Earth’s
magnetic field and produce effects on the ground like power outrages.
“These results are of particular interest for
solar wind formation. It indicates that the leading ideas for how to model the
formation of the solar wind are not complete, and so our ability to predict and
defend against space weather can be improved.” – Boe explained.
The next solar eclipse is for South America is expected in