The Solar Orbiter from the European Space Agency (ESA) could be making progress in uncovering the longstanding enigma of why the Sun's outer atmosphere is so hot.
On March 3, 2022, during the initial stage of Solar Orbiter's regular mission, the spacecraft's Extreme Ultraviolet Imager (EUI) obtained information that for the first time and revealed that a magnetic occurrence known as reconnection was happening repeatedly on a microscopic level.
Sun's Hot Outer Atmosphere
According to NASA, the Sun's outer atmosphere also known as the corona is the site of incredible temperatures that rise to over 2 million degrees Fahrenheit. By contrast, the layer below simmers at a temperature of 10,000 F.
The coronal heating problem, which concerns how the Sun manages to generate such high temperatures, remains an enigma to scientists studying the star. NASA's Parker Solar Probe mission aims to investigate the corona, gathering data to solve the problem and shedding light on the intriguing behavior of the Sun.
While the Sun looks calm and unperturbed from Earth, it is a flurry of activity, with solar eruptions and radiation bursts to send material hurtling through space. This activity can affect the functioning of satellites, communication systems, and potentially even power grids.
The corona, a layer that extends outward for millions of miles, is made up of incredibly hot plasma and gases that separate into ions and free electrons. Developing a comprehensive understanding of the coronal heating problem and the secrets of the Sun's atmosphere could therefore help scientists better comprehend the space around us and the star that powers life on Earth.
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Magnetic Reconnection in the Sun's Corona
The event on March 3, 2022, in which a spacecraft was positioned halfway between Earth and the Sun, allowed coordinated observations with NASA's Solar Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph (IRIS) missions, ESA reported.
The combined data from all three missions helped researchers to analyze magnetic reconnection, which occurs when a magnetic field transforms into a more stable configuration. This fundamental energy release mechanism is crucial in superheated gases known as plasmas and is thought to be the primary mechanism for powering large-scale solar eruptions.
Typically, magnetic reconnection is observed during large-scale, explosive phenomena. However, the recent event showed ultra-high-resolution observations of persistent small-scale reconnection in the corona, which is a long-lived, "gentle" sequence compared to the sudden explosive releases of energy that reconnection is usually associated with.
The event lasted an hour, and temperatures around the null point sustained themselves at around 10 million °C, generating an outflow of material in the form of discrete "blobs" that traveled away from the null point at around 80 km/s.
While this continuous outflow occurred, an explosive episode also took place around the null point, lasting four minutes. Solar Orbiter's results suggest that magnetic reconnection, at previously unresolvable scales, can occur continually in both gentle and explosive ways. This means that reconnection can persistently transfer mass and energy to the overlying corona, contributing to heating it.
The findings of the study, titled "Ultra-high-Resolution Observations of Persistent Null-point Reconnection in the Solar Corona" published in Nature, also imply that smaller and more frequent magnetic reconnections have yet to be detected. The idea is to detect them with even better spatiotemporal precision in the future around Solar Orbiter's closest approaches to determine how much heat is transmitted in this way.
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