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Analysis shows that mini jets of gas help to generate the solar wind, a discovery that also illuminates how our star’s activity damages satellites.
nature
By Alexandra Witze
24 August 2023
Tiny bursts of superheated gas could fuel the stream of charged particles that rushes outwards from the Sun’s surface at hundreds of kilometres per second, a study1 shows. The origin of this powerful ‘solar wind’ has been a mystery for decades.
The discovery reveals fresh details about where the wind begins and how it is created. This is important for understanding why the Sun occasionally belches out extremely large bursts of particles, which can wash over Earth and generate glowing auroras while also damaging satellites.
“What we are observing ... could actually be a substantial source of the solar wind,” says Lakshmi Pradeep Chitta, a solar physicist at the Max Planck Institute for Solar System Research in Göttingen, Germany. He and his colleagues describe the finding today in Science.
Solar Orbiter snapped pictures of the picoflare jets in March 2022, as the spacecraft whizzed past the Sun’s south pole. The high-resolution images reveal dark streaks, each a few hundred kilometres long, that appear and then, after 20–100 seconds, disappear. In that short lifespan, a jet emits as much energy as is consumed by 3,000–4,000 households in the United States over an entire year, Chitta says.
The jets appear to be expelling material outward from the Sun. As they flicker in and out of existence, they could be pushing large numbers of particles into space and thus fuelling the solar wind. The jets are probably powered by disturbances in the magnetic field of the million-degree solar plasma.
The researchers were able to spot the jets for the first time because Solar Orbiter was flying so close to the Sun — just 45 million kilometres away, closer than the orbit of Mercury. Since the spacecraft’s launch in 2020, it has been traveling in an elliptical orbit around the Sun that takes it on close passes twice a year. That ringside seat has allowed it to photograph never-before-seen structures, such as other kinds of small flares nicknamed ‘campfires’.
Chitta’s team observed the picoflare jets in just one location: a dark region known as a coronal hole. Such holes are temporary gaps in the Sun’s magnetic field that allow particles to stream outwards into space. Scientists have long considered them to be the source of the solar wind, without knowing exactly how they ejected matter. The discovery of picoflare jets in a single coronal hole suggests that they could be ubiquitous across the Sun, Chitta says. If so, then lots of little flares everywhere could add up to a substantial source of the solar wind.
The Sun is currently approaching, or might have already reached, the peak of its 11-year cycle of activity, when a high number of sunspots dapple its surface and there are frequent large solar flares, which are eruptions of radiation. This July and August, three of the largest solar flares thought to be possible, known as X-class flares, erupted from the Sun. The 7 August flare created a strong radio blackout on Earth that interfered with navigation signals.
The high levels of activity are giving solar scientists plenty to look at, says Andrei Zhukov, a solar physicist at the Royal Observatory of Belgium in Brussels, who works with Solar Orbiter. “Overall now it’s a gold mine.”
The solar wind is a fundamental feature of the sun and understanding how and where it is generated near the sun has proven elusive and has been a key focus of study for decades. Now, thanks to its superior instrumentation, Solar Orbiter has taken us an important step closer. Data from the Solar Orbiter's Extreme Ultraviolet Imager (EUI) instrument has shown mages of the sun's south pole taken by EUI on 30 March 2022 revealing a population of faint, short-lived picoflare jets that are associated with small jets of plasma being ejected from the sun's atmosphere, causing the solar wind.
Hartmann352
nature
By Alexandra Witze
24 August 2023
Tiny bursts of superheated gas could fuel the stream of charged particles that rushes outwards from the Sun’s surface at hundreds of kilometres per second, a study1 shows. The origin of this powerful ‘solar wind’ has been a mystery for decades.
The discovery reveals fresh details about where the wind begins and how it is created. This is important for understanding why the Sun occasionally belches out extremely large bursts of particles, which can wash over Earth and generate glowing auroras while also damaging satellites.
“What we are observing ... could actually be a substantial source of the solar wind,” says Lakshmi Pradeep Chitta, a solar physicist at the Max Planck Institute for Solar System Research in Göttingen, Germany. He and his colleagues describe the finding today in Science.
Sizzling hot mission
The scientists used the European Space Agency’s Solar Orbiter spacecraft to spot the newfound jets issuing from the Sun’s atmosphere. They dubbed them ‘picoflare jets’, because they have approximately one-trillionth the energy of the largest flares the Sun can produce, and the prefix ‘pico’ refers to 10–12.Solar Orbiter snapped pictures of the picoflare jets in March 2022, as the spacecraft whizzed past the Sun’s south pole. The high-resolution images reveal dark streaks, each a few hundred kilometres long, that appear and then, after 20–100 seconds, disappear. In that short lifespan, a jet emits as much energy as is consumed by 3,000–4,000 households in the United States over an entire year, Chitta says.
The jets appear to be expelling material outward from the Sun. As they flicker in and out of existence, they could be pushing large numbers of particles into space and thus fuelling the solar wind. The jets are probably powered by disturbances in the magnetic field of the million-degree solar plasma.
The researchers were able to spot the jets for the first time because Solar Orbiter was flying so close to the Sun — just 45 million kilometres away, closer than the orbit of Mercury. Since the spacecraft’s launch in 2020, it has been traveling in an elliptical orbit around the Sun that takes it on close passes twice a year. That ringside seat has allowed it to photograph never-before-seen structures, such as other kinds of small flares nicknamed ‘campfires’.
Chitta’s team observed the picoflare jets in just one location: a dark region known as a coronal hole. Such holes are temporary gaps in the Sun’s magnetic field that allow particles to stream outwards into space. Scientists have long considered them to be the source of the solar wind, without knowing exactly how they ejected matter. The discovery of picoflare jets in a single coronal hole suggests that they could be ubiquitous across the Sun, Chitta says. If so, then lots of little flares everywhere could add up to a substantial source of the solar wind.
Sun King
The finding is consistent with the picture emerging from other solar observatories, such as NASA’s Parker Solar Probe mission, which also regularly flies past the Sun for a close look. In March, the Parker team reported2 finding other small jets near the bottom of the Sun’s atmosphere. These also seem to inject energy into the solar wind. Seeing all these events “is helping us fill in the picture” of the many phenomena that contribute to the Sun’s activity, says Dan Seaton, a solar physicist at the Southwest Research Institute in Boulder, Colorado.The Sun is currently approaching, or might have already reached, the peak of its 11-year cycle of activity, when a high number of sunspots dapple its surface and there are frequent large solar flares, which are eruptions of radiation. This July and August, three of the largest solar flares thought to be possible, known as X-class flares, erupted from the Sun. The 7 August flare created a strong radio blackout on Earth that interfered with navigation signals.
The high levels of activity are giving solar scientists plenty to look at, says Andrei Zhukov, a solar physicist at the Royal Observatory of Belgium in Brussels, who works with Solar Orbiter. “Overall now it’s a gold mine.”
References
- Chitta, L. P. et al. Science 381, 867–872 (2023).
Article Google Scholar - Raouafi, N. E. et al. Astrophys. J. 945, 28 (2023).
The solar wind is a fundamental feature of the sun and understanding how and where it is generated near the sun has proven elusive and has been a key focus of study for decades. Now, thanks to its superior instrumentation, Solar Orbiter has taken us an important step closer. Data from the Solar Orbiter's Extreme Ultraviolet Imager (EUI) instrument has shown mages of the sun's south pole taken by EUI on 30 March 2022 revealing a population of faint, short-lived picoflare jets that are associated with small jets of plasma being ejected from the sun's atmosphere, causing the solar wind.
Hartmann352
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