An image of the Sun's outer atmosphere, the corona, was taken with the EUI instrument. EUI's High Resolution Imager works at the extreme ultraviolet wavelength 17.4 nm. The image shows a lot of the sun's surface. The diameter of the Earth is over 12 thousand kilometres. The Sun was quiet on 23 February 2021, but HRIEUV still captured small-scale jet activity. The activity is associated with the so-called campfires, which are miniature solar flares that scientists discovered on the Sun with the EUI instrument shortly after Solar Orbiter's launch. The Solar Orbiter/EUI Team is a credit.
Solar Orbiter has generated a lot of great science, even though it hasn't entered its main science phase. The results from the mission's cruise phase were published today.
The AGU meeting has a special issue of Astronomy and Astrophysics, and there are more than fifty papers presented today.
The results published today demonstrate the variety of solar science that the mission is making possible, and signals the wealth of data that is now flowing back to Earth.
The cruise phase of Solar Orbiter began in June 2020. The data from the in-situ instruments was used to measure the environment around the spacecraft. It used its remote sensor to look at the sun in order to calibrate the instruments. The first scientific studies to be undertaken were enabled by some of the data that turned out to be of good quality.
The solar campfires are more detailed.
The scientists nicknamed the flares "campfires" because they were discovered by the EUI after it first opened its eyes. The corona, the outer atmosphere of the sun, has been a mystery for many decades.
In the latest results, the EUI instrument has been returning an image of the solar corona every two seconds. The solar corona has never before been recorded in the extreme ultraviolet. The data shows a class of campfires that shoot out jets of gas at speeds of a hundred kilometers per second. The jets are only observed for a short time.
The movie shows how the EUI instrument on Solar Orbiter studies the sun, zooming in on short-lived brightening events. The Solar Orbiter/EUI Team is a credit.
"We are now getting to the essence of this process," says Pradeep Chitta, who led this study. The past is like having bad eyesight and only being able to see blurred images. The campfires are being brought into sharper focus by EUI.
The view will only get better as Solar Orbiter gets closer to the sun. Thanks to an upgrade at the ground stations, the spacecraft can beam back more of the high data than anticipated before launch.
The first widespread energetic particle event of the Solar Orbiter.
The first large-scale event has also been witnessed by Solar Orbiter. The first widespread energetic particle event burst from the sun on November 29, 2020.
The first widespread energetic particle event of cycle 25 occurred during this particular event on the sun. The event spread particles across the inner solar system. By the time the eruption reached Earth's distance, the ejected particles were spread over more than 200 degrees of solar longitude.
They were found by the Solar Orbiter, as well as by NASA's STEREO-A, and the other satellites that were close to Earth's orbit. How big was the source region on the sun, and how much did the eruption grow after it was released? This is where Solar Orbiter's goal of linkage science becomes important.
Alexander Kolhoff is the leader of the analysis of the November event. We see a particle event around the spacecraft and then we go to the remote sensed observations and try to find the source on the sun.
The data is not conclusive about whether the source region was large enough to explain the spread of particles or not. The scientists are continuing to refine this technique and the hints in the data show great promise.
The EUI instrument onboard Solar Orbiter took a movie of the sun's corona. The instrument returned an image every two seconds. The movie is one of the highest quality observations of the solar corona ever made. It shows a class of miniature solar flares that shoot out jets of gas at speeds of a hundred kilometres per second. The jets can only be seen for a short time. They could be involved in explaining how the corona is heated. Explaining the extreme temperature has been a focus for solar scientists for many decades. The Solar Orbiter/EUI Team is a credit.
Tracking down the solar invisible CMEs.
The Mullard Space Science Laboratory, University College London, UK, had a researcher named Jennifer O'Kane who made detailed observations of the solar surface. She and her colleagues went to look for so-called stealth CMEs.
There is a term for the mass ejection from the sun. These are the giant eruptions of the sun's magnetic field that occur with solar flares, which are an explosion of magnetic particles in the sun's lower atmosphere. In the case of a stealth CME, there is no Flare.
Using the most sophisticated image processing tools available, she looked at solar images to see if she could find evidence of a triggering event.
The magnetic field strength of the sun was double that of a normal CME, but the puzzle was that the sun's visible surface was completely blank at that time. There were no active regions. The high magnetic field strength of the sun's corona made the team aware of it.
A dark region in the extreme ultraviolet images that showed a low-density corona that lifted off very slowly from the sun was found after a long search.
Slow is a relative term. This one was moving at a rate of tens of kilometers per second.
The first widespread energetic particle event burst from the Sun on November 29, 2020. The movie of the event was captured by the LASCO instrument. The NASA SOHO/LASCO team is credited.
"It was the most difficult event I've ever studied, and it took a lot of effort to find a hint of its origin," says Jennifer.
Calculating space weather in real time is a challenge because they rely on seeing something on the sun that they can recognize in real time.
The comet's tail is being pointed at.
Lorenzo Matteini, Imperial College London, UK, led another investigation to determine if the Solar Orbiter crossed the tail of the comet.
The team had to make sure that instruments were ready in time for the crossing because it was predicted after Solar Orbiter's launch. The comet disintegrated ten days before the crossing, and the tail faded.
Lorenzo and his colleagues found evidence of a crossing of the comet's tail remnant. If the sun's magnetic field were draped around a piece of the broken comet's nucleus, the magnetic field around Solar Orbiter would suddenly change its polarity.
Lorenzo says that this is the first time that a comet tail has been seen inside Earth's orbit.
The sun is magnetic. NASA/SDO/Goddard is a credit.
It may not be the last. There are comets falling towards the sun. The way they interact with the sun's magnetic field provides another way for Solar Orbiter to investigate this fascinating region of the solar system.
The main science phase of the Solar Orbiter is now underway. The sun will pass by in March of 2022.
The mission was a pleasure to work on. The results show how much great science has already been done and how much more is to come.
The Solar Orbiter First Results (Cruise Phase) can be found at aanda.org.
Astronomy and Astrophysics are in the journal.
The solar-orbiter publishes a wealth of science results from its cruise phase.
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