Under the arch of a huge coronal loopabundance of exotic solar phenomena active in the transition zone between sthe lower atmosphere of the UNchromosphere and corona, are captured in this magical video by European Space Agency‘c Solar Orbiter spacecraft.
The view, recorded by Solar Orbiter from a distance of just over 43 million kilometers (26.7 miles) from the sun, reveals features of the sun’s surface that we could only dream of 10 years ago. That’s because the Solar Orbiter and its NASA colleague, the Parker solar probeare meant to watch the sun from much closer proximity than any other mission before them.
In fact, Solar Orbiter reached its closest point to the sun 10 days after this video was taken. The Parker Solar Probe will reach its closest point, just 6.9 million kilometers (4.3 million miles) away, on Christmas Eve later this year. This may still sound like a huge distance, but when you consider that the sun is 1.39 million kilometers (864,600 miles)., it’s not that far at all. It’s so close, in fact, that the Parker Solar Probe will skirt the edge of the corona and withstand temperatures of 1,377 degrees Celsius (2,500 degrees Fahrenheit).
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But back to the Solar Orbiter. This video taken on September 27, 2023 with the spacecraft’s Ultraviolet Imager (EUI) shows several different types of features. The things to remember are that most of the sun’s activity is driven by the massive solar magnetism, and that much of that activity involves such high temperatures that it emits mostly ultraviolet light. When the movie starts, the first noticeable feature you can see is a bright spot in the lower left corner. This is called “coronal moss”. They are usually found at the base of coronal loops, which are magnetic loops that penetrate from the visible surface of the sun (the photosphere) and form bridges across active regions that transport plasma (ionized or electrified gas) as hot as millions of degrees. Moss is so named because when solar physicists first discovered it, it was a porous-looking feature.
However, Solar Orbiter’s high-resolution view shows that the moss is instead a tangle of lace-like strands of plasma that follow a mix of magnetic field lines at the base of the loop, which is the location of the “active region”. These regions are where sun spots can also be detected, although sunspots are too cool to see in the ultraviolet light of this video. The brightest areas in the moss radiate over a million degrees.
On the horizon of the solar limb we can see dark, spikes. These hair-like structures are called spicules, and they are jets of plasma 300 kilometers (185 mi) in diameter that can reach heights of 10,000 kilometers (6,200 mi) above the photosphere; they wave time with the sun’s slightly oscillating magnetic field. Racing upwards at speeds between 15 kilometers per hour and 110 kilometers per hour (9 miles per hour and 68 miles per hour), the millions of spicules that are present on the sun at any given moment deposit vast amounts of plasma into the chromosphere and corona.
Twenty-two seconds into the video, something else happens. You will see an outburst of cooler material rising as a plume deep into the chromosphere before falling back to the photosphere. The violence and scale of this outbreak are extraordinary; it may seem modest compared to the rest of the sun, but this one flare is bigger than our entire Earth.
Towards the end of the video, you may catch another elusive solar phenomenon: a coronal shower. Despite the name, it is not water. It consists of droplets formed by huge clumps of plasma, 10,000 degrees Celsius (18,000 degrees Fahrenheit) hot, falling from the coronal loop back into the photosphere. The coronal shower appears dark only because, unlike the million-degree hot corona around it, the shower is relatively cold, creating a contrasting effect similar to dark sunspots.
What happens in the sun has consequences further inland solar systembecause ultimately much of the energy seen here in this video is unleashed in the space by driving the Solar wind, made of charged particles. This solar wind meets spaceships, planets and moons interacting with them (this gives rise to polar Lights, for example). Solar Orbiter and Parker Solar Probe were able to team up to study the solar wind, and it just so happened that when Solar Orbiter captured this video, Parker Solar Probe was only 7.26 million kilometers (4.51 million miles) from the sun – Parker soon sensed the solar wind leaving the sun after recording this activity. With Solar Orbiter investigating the source of the solar wind and where it gets its energy, and the Parker Solar Probe measuring the gusts of the wind, solar physicists are able to get a clearer picture of how the solar wind forms and evolves as it moves away from our star.
