The Solar Orbiter spacecraft has discovered tiny jets that can drive the solar wind

ESA/NASA The Solar Orbiter spacecraft has detected several small jets of material ejected from the Sun’s outer atmosphere. Each jet lasts from 20 to 100 seconds and exhausts Plasma At speeds of about 100 km/s (60 miles/s) or 360,000 km/h (220,000 mph), these jets may be the long-lived source of the solar wind.

Understanding the solar wind

The solar wind is made up of charged particles called plasma that are constantly being ejected from the Sun. It spreads outward through interplanetary space, colliding with anything in its path. When the solar wind collides with Earth’s magnetic field, it creates the aurora.

Although the solar wind is a fundamental feature of the Sun, understanding how and where it forms near the Sun has proven elusive and has been a major focus of study for decades. Now, thanks to its excellent instruments, the Solar Orbiter has brought us an important step closer.

This mosaic of images shows numerous small jets of material ejected from the Sun’s outer atmosphere. Images are from the ESA/NASA Solar Orbiter spacecraft. They are shown as dark lines on the solar surface in this mosaic. Although the images are ‘negative’ i.e. the jets are shown dark, they are a bright flash against the solar surface. Credit: ESA & NASA/Solar Orbiter/EUI Group; Credit: Lakshmi Pradeep Chitta, Max Planck Institute for Solar System Research, CC BY-SA 3.0 IGO

High-resolution imaging of the Sun’s surface

The data comes from the Solar Orbiter’s Extreme Ultraviolet Imager (EUI) instrument. Images of the Sun’s south pole taken by EUI on March 30, 2022 reveal a number of faint, short-lived features associated with small jets of plasma ejected from the Sun’s atmosphere.

“We were only able to detect these small jets because of the unprecedented high-resolution, high-cadence images produced by EUI,” says Lakshmi Pradeep Chitta of Germany’s Max Planck Institute for Solar System Research and lead author of the paper describing the work. . Specifically, the images were taken in the extreme ultraviolet channel of EUI’s High Resolution Imager, which monitors million-degree solar plasma at a wavelength of 17.4 nanometers.

Notably, the analysis shows that these features are caused by the ejection of plasma from the solar atmosphere.

This movie was created from observations taken by the ESA/NASA Solar Orbiter between 04:30 and 04:55 on March 30, 2022. UTC, and was previously published last year. It shows a ‘coronal hole’ near the Sun’s south pole. Subsequent analysis revealed several small jets released during the observation. They appear as small flashes of bright light throughout the film. Each ejects charged particles called plasma into space. The circle represents the size of the Earth. Credit: ESA & NASA/Solar Orbiter/EUI Group; Credit: Lakshmi Pradeep Chitta, Max Planck Institute for Solar System Research

Magnetic structures and the solar wind

Researchers have known for decades that a significant portion of the solar wind is associated with magnetic structures called coronal holes—regions where the Sun’s magnetic field does not return back into the Sun. Instead, the magnetic field extends deeper into the solar system.

Plasma flows along these ‘open’ magnetic field lines and travels to the solar system, forming the solar wind. But the question is: How did the plasma get started?

The traditional assumption is that as the corona heats up, it naturally expands and part of it escapes into the field. But these new results look at the coronal hole located at the Sun’s south pole, and the revealed individual jets challenge the assumption that the solar wind forms only in a steady continuous flow.

“One of the conclusions here is that the flow is not really uniform to a large extent, and the ubiquity of jets suggests that the solar wind may form a very intermittent outflow from coronal holes,” says Andre Zhukov of the Royal Observatory of Belgium. , a collaborator on the mission that led the Solar Orbiter Observation Campaign.

ESA’s Solar Orbiter mission will encounter the Sun from its closest orbit around Mercury. Credit: ESA/ATG medialab

Energy Analysis of Jets

The energy associated with each jet is small. At the upper end of coronal events are X-class solar flares and at the lower end are nanoflares. An X-flare has a billion times the energy of a nanoflare. The tiny jets detected by the Solar Orbiter are even less energetic, exhibiting a thousand times less energy than a nanoflare, and expelling much of that energy into the plasma.

They are ubiquitous, with new observations suggesting that they eject a significant fraction of the material we see in the solar wind. And smaller, more frequent events may be even more.

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

Future observations and broader implications

Currently, the Solar Orbiter is still orbiting the Sun near its equator. So in these observations, the EUI looks at the South Pole from a grazing angle.

“Some of the properties of these tiny jets are hard to measure when viewed edge-on, but in a few years, we’ll see them from a different perspective than any other telescopes or observatories, so together that should help a lot,” he says. Daniel Müller, ESA Project Scientist for the Solar Orbiter.

Because as the mission continues, the spacecraft will It gradually tilts in its orbit Towards the polar regions. At the same time, the Sun’s activity will progress through the solar cycle and coronal holes will begin to appear at different latitudes, providing a unique new perspective.

As this work extends beyond our own solar system, everyone involved will be eager to see what new insights they can glean.

Only the Sun can observe its atmosphere in such detail, but the same process is likely at work in other stars. This makes these observations the discovery of a fundamental astrophysical process.

Reference: LB Chitta, AN Zhukov, D Bergmans, H Peter, S Parenti, S Mandal, R Asner Cuadrado, U Schuhle, L. Deriaga, F. Acher, K. Barczynski, E. Buchlin, Harrah L, Kraaikamp E, Long DM, Rodriguez L, Schwanitz C, Smith PJ, Verbeeck C, and Seaton DB. Science.
DOI: 10.1126/science.ade5801

Solar Orbiter is a space mission of international collaboration between ESA and NASA, operated by ESA.