60-Year-Old Mystery of Sun’s Magnetic Waves Now Cracked

X-rays stream off the Sun in this image showing observations using NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, overlaid on a picture taken by NASA's Solar Dynamics Observatory (SDO). (Image: NASA)
X-rays stream off the Sun in this image showing observations using NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, overlaid on a picture taken by NASA's Solar Dynamics Observatory (SDO). (Image: NASA)

A Queen’s University Belfast scientist has led an international team to the ground-breaking discovery of why the Sun’s magnetic waves strengthen and grow as they emerge from its surface. The findings could help to solve the mystery of how the corona of the Sun maintains its multi-million-degree temperatures.

For more than 60 years, observations of the Sun have shown that as the magnetic waves leave the interior of the Sun, they grow in strength, but until now there has been no solid observational evidence as to why this was the case.

The corona’s high temperatures have also always been a mystery. Usually, the closer we are to a heat source, the warmer we feel. However, this is the opposite of what seems to happen on the Sun — its outer layers are warmer than the heat source at its surface.

This ultraviolet image, captured by NASA’s Solar Terrestrial Relations Observatory (STEREO) Ahead spacecraft on February 12, 2010, shows solar storms brewing in two active areas of the Sun. NASA image courtesy the STEREO science team. Caption by the STEREO science team and Holli Riebeek)

This ultraviolet image, captured by NASA’s Solar Terrestrial Relations Observatory (STEREO) Ahead spacecraft on February 12, 2010, shows solar storms brewing in two active areas of the Sun. (Image: NASA image courtesy the STEREO science team. Caption by the STEREO science team and Holli Riebeek)

Scientists have accepted for a long time that magnetic waves channel energy from the Sun’s vast interior energy reservoir, which is powered by nuclear fusion, up into the outer regions of its atmosphere. Therefore, understanding how the wave motion is generated and spread throughout the Sun is of huge importance to researchers.

The team, which was led by Queen’s, included 13 scientists spanning five countries and 11 research institutes, including the University of Exeter; Northumbria University; the European Space Agency; Instituto de Astrofísica de Canarias, Spain;  the University of Oslo, Norway; the Italian Space Agency; and California State University Northridge, USA.

The sun’s corona — its outermost layer of atmosphere. Image: Dr. Richard Morton, Northumbria University Newcastle)

The sun’s corona — its outermost layer of atmosphere. (Image: Dr. Richard Morton, Northumbria University Newcastle)

The experts formed a consortium called “Waves in the Lower Solar Atmosphere (WaLSA)” to carry out the research and used advanced high-resolution observations from the National Science Foundation’s Dunn Solar Telescope, New Mexico, to study the waves.

Dr. David Jess from the School of Mathematics and Physics at Queen’s led the team of experts. He explains:

The team then used supercomputers to analyze the data through simulations. They found that the wave amplification process can be attributed to the formation of an “acoustic resonator,” where significant changes in temperature between the surface of the Sun and its outer corona create boundaries that are partially reflective and act to trap the waves, allowing them to intensify and dramatically grow in strength.

NASA's Solar Dynamics Observatory captured an image of the massive flare that burst off the sun on Sept. 10, 2017. (Image: ©NASA/Goddard/SDO)

NASA’s Solar Dynamics Observatory captured an image of the massive flare that burst off the sun on Sept. 10, 2017.
(Image: ©NASA/Goddard/SDO)

The experts also found that the thickness of the resonance cavity — the distance between the significant temperature changes — is one of the main factors governing the characteristics of the detected wave motion Dr. Jess said:

Dr. Ben Snow, from the University of Exeter and a co-author of the study, said:

The findings of the study have been published in Nature Astronomy. Funding for the study was provided by the Science and Technology Facilities Council, Randox Laboratories Ltd., Ministerio de Economía y Competitividad, Invest Northern Ireland, the Department for Employment and Learning in Northern Ireland, EC | Horizon 2020 Framework Programme, and Norges Forskningsråd.

Plans are now being made by the global physics community to make further investigations using the newest-generation solar telescopes that will become available over the next few years. This includes the upcoming Daniel K. Inouye Solar Telescope, a $300 million observatory currently nearing completion in Hawaii.

Provided by: Queen’s University Belfast [Note: Materials may be edited for content and length.]

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