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.
“The 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.
He discovered 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.
Boe 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.
The results 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 December 2020.