Published on April 4, 2019
When Simone Di Matteo first saw the patterns in her data, it seemed too good to be true. "It's too perfect!" Di Matteo, a space physicist at the University of Aquila in Italy, remembered thinking. "It can not be real." And it was not, he would soon discover it.
Di Matteo's research was the beginning of a project that NASA scientists undertook in anticipation of the first data of NASA's Parker Solar Probe mission, which was launched in 2018.
Over the next seven years, Parker will fly through unexplored territory, at a distance of only 4 million miles from the Sun. Before Parker, the Helios 2 satellite had the closest approach to the Sun at 27 million miles. , and the scientists thought that it could give them an idea of what to expect.
"When a mission like Parker goes to see things that nobody has seen before, only a hint of what could be observed is really useful," Di Matteo said.
Di Matteo was looking for long trains of mbadive bubbles, like the otherworldly bubbles of a lava lamp, but 50 to 500 times the size of Earth, in the solar wind. The solar wind, whose origins are not yet fully understood, is the stream of charged particles that constantly blow from the Sun. The Earth's magnetic field, called the magnetosphere, protects our planet from the impact of its radiation. But when giant drops of solar wind collide with the magnetosphere, they can trigger disturbances that interfere with satellites and daily communication signals.
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In his search, Di Matteo was reexamining the file data of the two Helios ships of NASA-Germany, which were launched in 1974 and 1976 to study the Sun. But this was a 45-year-old data that he had never worked with before. . The impeccable and undulating patterns he initially found hinted that something was diverting him.
Di Matteo did not find exactly what he was looking for until he discovered and eliminated those false patterns: dotted trails of spots that sprouted from the Sun every 90 minutes or so. The scientists published their findings at JGR Space Physics on February 21, 2019. They think the spots could shed light on the beginnings of the solar wind. Any process that sends the solar wind from the Sun must leave signatures in the bubbles.
Opening the way to the new science
The problem with studying the solar wind of the Earth is the distance. In the time it takes the solar wind to run along the 93 million miles between us and the Sun, important clues about the origins of wind, such as temperature and density, vanish. "You're constantly wondering:" How much of what I'm seeing here is due to evolution during four days in transit, and how much did it come directly from the Sun? ", Said solar scientist Nicholeen Viall, who advised Di Matteo during his research at NASA's Goddard Space Flight Center in Greenbelt, Maryland. The Helios data, some of which were collected in only a third of the distance between the Sun and Earth, could help them begin to answer these questions.
The first step was to trace the Helios measurements of the spots to their source on the Sun. "You can look at the data from the spacecraft as much as you want, but if you can reconnect them with the Sun, they tell a more complete story," said Samantha Wallace, one of the study collaborators and Physics Ph.D. . Student at the University of New Mexico in Albuquerque.
Wallace used an advanced solar wind model to link magnetic maps of the solar surface with observations of Helios, a difficult task since computer languages and data conventions have changed a lot since the days of Helios. Now, researchers were able to see what kind of regions on the Sun would likely turn into solar wind droplets.
Sift the evidence
Then, Di Matteo searched the data for specific wave patterns. They waited for the conditions to alternate (hot and dense, then cold and dim) as individual bubbles enveloped the ship and moved on, in a long line.
The perfect image patterns Di Matteo found for the first time worried him. "That was a red flag," said Viall. "The real solar wind does not have such precise and clean periodicities, and usually when you get such a precise frequency, it means that some instrument effect is occurring." Maybe there was some element of the design of the instrument that they were not considering, and was imparting effects that should be separated from the real patterns of the solar wind.
Di Matteo needed more information about the Helios instruments. But most of the researchers who worked on the mission have retired a long time ago. He did what any other person would do, and resorted to the internet.
Many searches on Google and a weekend of online translators later, Di Matteo unearthed an instruction manual in German that describes the instruments dedicated to the solar wind experiment of the mission. Decades ago, when Helios was simply a plan and before someone launched a ship to the Sun, scientists did not know what was the best way to measure the solar wind. To prepare for different scenarios, Di Matteo learned, they equipped the probes with two different instruments that would measure certain properties of the solar wind in their own way. This was the culprit responsible for the perfect waves of Di Matteo: the spacecraft itself, since it alternated between two instruments.
After removing the data segments taken during the routine change of the instruments, the researchers looked for the spots again. This time, they found them. The team describes five cases in which Helios went on to trap bubble trains. While scientists have seen these spots on Earth before, this is the first time they have studied them so close to the Sun and at this level of detail. They present the first conclusive evidence that the bubbles are hotter and denser than the typical solar wind.
Return of the Blobs
If Blob trains bubbles at 90-minute intervals continuously or in jets, and how much they vary between them, it remains a mystery. "This is one of those studies that generated more questions than we answered, but that's perfect for Parker Solar Probe," said Viall.
Parker Solar Probe aims to study the Sun closely, seeking answers to basic questions about the solar wind. "This will be very useful," said Aleida Higginson, a deputy project scientist at the Applied Physics Laboratory at Johns Hopkins University in Laurel, Maryland. "If you want to start understanding things you've never seen before, you need to know what we measured earlier and have a solid scientific interpretation for it."
Parker Solar Probe makes its second solar flyby on April 4, which takes it to 15 million miles from the Sun, which already reduces the record distance of Helios 2 by half. The researchers are anxious to see if spots appear in Parker's observations. Eventually, the ship will get so close that it could catch spots just after they have formed, fresh from the Sun.
The Daily Galaxy through the NASA / Goddard Space Flight Center
Image at the top of the page: Coronal eruption with thanks to physik.uni-graz.at/en