Solar Orbiter finds plasma jets that may fuel solar wind

Solar Orbiter, the next-generation sun explorer, has found a promising clue about the origin of the solar winds.
Mrigakshi Dixit
Tiny jets escape the Sun
Tiny jets escape the Sun

ESA & NASA/Solar Orbiter/EUI Team 

The Sun is a dynamic star that incessantly emits a high amount of energy into space. Our host star lies at the heart of our solar system, but it holds back many secrets about what’s happening inside it. 

Solar scientists are now able to solve some of the Sun's long-standing mysteries thanks to a fleet of orbiting missions meant to investigate its dynamics. 

One such long-unsolved enigma that has baffled scientists is the origin of solar winds, a continuous stream of charged particles, such as plasma, rushing from the Sun's outer atmosphere across the solar system. 

Now, Solar Orbiter, the next-generation sun explorer, has found a promising clue about the origin of the solar winds. 

The probe has discovered small, brief energy jets known as "picoflare jets" escaping the Sun's outer atmosphere, or corona. Astronomers suspect that these plasma jets could be the source of the solar wind. 

Study of ultra-violet images of the Sun's south pole

Solar winds have been known for decades, but astronomers have never been convinced of how they arise near the Sun, making it one of the most challenging riddles to answer. 

For this study, scientists examined the latest data and imagery acquired by the probe's advanced Extreme Ultraviolet Imager, or EUI. The instrument took measurements when the spacecraft was at a distance of roughly 31 million miles (50 million kilometers) from the star on March 30, 2022.

These ultraviolet, high-resolution images of the Sun's south pole indicate a bunch of faint, miniature, transient jet structures that blast the solar wind.

According to the European Space Agency (ESA), these relatively brief jets last only seconds — between 20 and 100 seconds — and spew plasma at speeds of up to 100 km/s. 

“We could only detect these tiny jets because of the unprecedented high-resolution, high-cadence images produced by EUI,” said Lakshmi Pradeep Chitta, Max Planck Institute for Solar System Research, Germany, and the principal author of this study, in an official release. 

Coronal holes consist of tiny plasma jets

Previously, the solar wind has been linked to magnetic structures called coronal holes, which form at any moment and any location on the Sun's surface. These are vast spots with open magnetic fields that do not circle back or create loops. 

This open, magnetic field line arrangement allows solar wind to escape more efficiently throughout the solar system. 

The new study reveals that picojets in coronal holes could be formed by magnetic reconnection, which refers to the breaking and rejoining of magnetic field lines. This phenomenon eventually releases a massive quantity of stored energy in the coronal holes. This activity is, in fact, a fundamental mechanism for stars.

One of the key findings of the observation was the presence of tiny individual jets in the coronal hole at the South Pole. After a thorough examination, the authors concluded that each of these small jets is a significant energy source and matter for solar winds. They also stated that the tiny plasma jets were surprisingly visible even in the darkest sections of coronal holes.

It was long assumed that solar wind is only created in a steady, continuous flow, which is not totally correct. 

“One of the results here is that to a large extent, this flow is not actually uniform, the ubiquity of the jets suggests that the solar wind from coronal holes might originate as a highly intermittent outflow,” explained Andrei Zhukov, Royal Observatory of Belgium, a collaborator on the work who led the Solar Orbiter observing campaign.

Apart from shedding light on the solar wind, these findings might one day help to explain why the Sun's outer atmosphere is thousands of times hotter than its surface. 

Solar Orbiter finds plasma jets that may fuel solar wind
ESA-NASA's Solar Orbiter

Launched in 2020, the Solar Orbiter is the first space mission to study solar plasma. 

The mission is a collaboration between NASA and the ESA that relies on 10 high-tech equipment to collect data and capture images of the Sun's north and south poles.

Knowledge of the Sun’s dynamics, including its magnetic field and solar wind, is pivotal in understanding its influence on the Earth and other solar system planets. Its powerful radiation could also impact GPS and telecommunications and the functioning of low-Earth orbit objects such as satellites and the International Space Station. 

The results have been published in the journal Science.

Study abstract:

Coronal holes are areas on the Sun with open magnetic field lines. They are a source region of the solar wind, but how the wind emerges from coronal holes is not known. We observed a coronal hole using the Extreme Ultraviolet Imager on the Solar Orbiter spacecraft. We identified jets on scales of a few hundred kilometers, which last 20 to 100 seconds and reach speeds of ~100 kilometers per second. The jets are powered by magnetic reconnection and have kinetic energy in the picoflare range. They are intermittent but widespread within the observed coronal hole. We suggest that such picoflare jets could produce enough high-temperature plasma to sustain the solar wind and that the wind emerges from coronal holes as a highly intermittent outflow at small scales.

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