Solar Orbiter’s recent perihelion passage in October 2022 provided us with remarkable close-up images of the sun, shedding light on the intriguing phenomenon of how the solar corona, the sun’s outer atmosphere, reaches temperatures exceeding a million degrees Celsius while the surface remains at around 6000 degrees Celsius. The source of this temperature difference has puzzled scientists for a long time.
While magnetic fields were always suspected to play a crucial role, the precise mechanisms have remained a mystery. The new images have given us valuable insights, revealing that the million-degree gas loops that make up the solar corona are closely connected to small 100-km-sized magnetic field patches on the sun’s surface.
These images were captured by two of Solar Orbiter’s instruments. The yellow image from the Extreme Ultraviolet Imager (EUI) vividly displays the arch-like hot plasma loops extending into the solar corona. The speckled image, courtesy of the Polarimetric and Helioseismic Imager (PHI), reveals the magnetic polarity of the sun’s surface, with red and blue areas denoting north and south polarities. What’s fascinating is the clear correlation between these small magnetic field patches and the coronal loops.
These coronal loops seem to be intricately linked to scattered patches of small-scale magnetic fields on the sun’s surface, often exhibiting mixed polarities. The complex arrangement and temporal changes of these magnetic field patches appear to be key factors in the formation of the scorching-hot solar corona.
What makes these observations even more exciting is that they were captured at a remarkably high spatial resolution of approximately 200 kilometers, enabling a close comparison of data from both instruments. With this unique data in hand, solar physicists now have a valuable opportunity to explore the role of these small-scale magnetic fields in the creation of the solar corona.
As Solar Orbiter prepares for another close encounter with the sun on October 7, 2023, coming as close as 43 million kilometers to our star (closer than Mercury), it promises to unveil previously unseen small-scale processes that contribute significantly to the sun’s blistering atmosphere. This upcoming event holds the potential to expand our understanding of the sun’s intricate workings even further.
Source: European Space Agency