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Astronomy: Here comes the Sun in high resolution *IMAGES & VIDEOS*
The highest resolution observations of the Sun’s visible surface reported to date are presented in Nature. The time-sequenced images provide a far more complex picture of the Sun’s surface layer than previously seen, giving new insights into the magnetically active regions within this layer.
The Sun’s visible surface (known as the photosphere) is a thin layer of its atmosphere where the fluid plasma becomes transparent, allowing light to escape. This region is known to be dynamic and complex, with many factors such as magnetic field and convection currents shaping the organization of the atmosphere.
David Kuridze, Friedrich Woeger, and colleagues use the Daniel K. Inouye Solar Telescope, Hawaii, USA to obtain the highest spatial resolution observations of the Sun’s visible surface acquired to date. The studied region is a magnetically active area close to a sunspot. In the new high-resolution images, the solar surface appears dominated by band-like and vortex-like structures. The authors associate these features with Kelvin–Helmholtz instabilities, a classic fluid dynamics phenomenon in which rippled structures form when two fluids slide past each other at different speeds. This provides the first known confirmation of this phenomenon on the solar surface.
This discovery has implications for our understanding of how magnetic fields function in solar objects such as the Sun.
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Dr Tulasi Parashar, Senior Lecturer in Physics, Victoria University of Wellington
"The Sun’s atmosphere, also known as the Solar corona, is much hotter than the Sun’s surface: ~2,000,000 °C vs ~6,000 °C. How is energy transported from the colder surface of the Sun to much hotter corona? This problem has stumped scientists for about eight decades. Scientists have theorised waves, turbulence, and something called the nano-flares as candiates to heat the Solar corona.
"The paper uses very high resolution observations of the Sun’s surface to study the time evolution of granule-like structures and their boundaries near an active region. These high resolution images show signs of an instability called the Kelvin Helmholtz instability (KHI). This instability is common in both electrically charged fluids (like in the Sun) and uncharged fluids. Whether we know its name or not, most of us would have seen KHI in images of clouds curling up into trains of vortices. The authors perform incredible detective work in processing the observations and then quantitatively studying the properties of the KHI. Simulations presented in the paper further confirm that what is observed is indeed KHI.
"These results have profound implications for the dynamics of the corona and subsequently the problem of how it is heated. The KHI can twist and knot magnetic fields in the lower corona to produce "braids" which can "reconnect" and produce nano-flares. Continued excitation of KHI at the granular level can stir turbulence in the solar corona, which further enables the possibilities of the nano-flares.
"These observations will motivate further investigations into the turbulent nature of magnetic fields in the lower corona and the physics that transfers energy from the colder surface of the Sun to the much hotter corona."
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