The Orbiter spacecraft discovers small jets on the sun that can power the solar wind

The Solar Orbiter spacecraft has discovered what could be the sought-after origin of the solar wind tiny jets of material emanating from the sun last between 20 and 100 seconds and eject plasma at a speed of about 100 km/s.

The solar wind, formed of plasma or charged particles, leaves the solar atmosphere (or corona) and travels through space, colliding with everything in its path. When it passes through the Earth’s magnetic field, it generates the Northern Lights.

Understanding how and where the solar wind is generated has been the subject of research for decades. Now the ESA and NASA Solar Orbiter probe has made an important discovery, the details of which were published this Thursday in the journal Science.

In March 2022, Solar Orbiter’s EUI (Extreme Ultraviolet Imager) instrument, which observes solar plasma at a wavelength of 17.4 nanometers, captured images of the sun’s south pole, showing numerous small plasma jets. They escaped from the sun’s atmosphere.

It has been known for decades that a significant portion of the solar wind is associated with coronal holes, regions in which the sun’s magnetic field does not retreat into the body’s interior, but is directed toward the solar system.

But What is it that launches the plasma? The traditional hypothesis is that because the corona is hot, it naturally expands and some of it escapes along the magnetic field. But observations from the Solar Orbiter have challenged the assumption that the solar wind only exists in a continuous stream and stable.

“One of the results obtained here is that this flow is not really uniform to a large extent; the ubiquity of the jets suggests that the solar wind emanating from the coronal holes could originate as a very periodic outflow,” explains Andrei Zhukov out. , of the Royal Observatory of Belgium, employee at work.

Different levels of solar energy

The energy associated with each individual jet is small: the largest are the X class solar flares and the smallest are nanoflares.

The tiny jets discovered by Solar Orbiter are even less energetic than nanoflares and contain about a thousand times less energy than the latter.

However, the ubiquity of these jets suggests that they eject a substantial amount of material from the solar wind. And there may be even smaller, more frequent events that add even more, the authors said.

“I think it’s an important step to find something in the disk that definitely contributes to the solar wind,” said David Berghmans of the Royal Observatory of Belgium, and principal investigator of the EUI instrument.

Solar Orbiter is currently close to the sun’s equator, but as the mission progresses, the spacecraft will tilt toward the polar regions as the sun’s activity continues throughout the solar cycle and coronal holes begin to appear at many different latitudes, and that will be a unique new perspective.

“In a few years we will see these jets from a different perspective than any other telescope or observatory, so all this together should help a lot,” said Daniel Müller, ESA’s Solar Orbiter scientist.

And since the sun is one star, the same process is likely to occur with other stars as well. These observations may thus represent the discovery of a fundamental astrophysical process, the authors conclude. (JO)

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