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New research has created an entire catalog of mysterious, slow-forming, ultra-hot explosions from the sun’s atmosphere. The findings suggest that a substantial number of these strangely lethargic flares, which were first discovered in the 1980s, warrant further investigation.
Solar flares are bursts of energy that occur when the sun’s magnetic field lines tangle or cross, then break up and reconnect around dark spots called sunspots. These radiation flows, when strong enough, can damage satellites and even affect electrical and communications infrastructure here on Earth.
Solar flares that last from a few minutes to a few hours are traditionally classified by the amount of energy they emit. However, this new research differentiated solar flares based on the rate at which their energy actually builds up, showing that many solar flares do not release energy as quickly as the crack of a whip and then slowly dissipate, as shown the standard image of these. events suggest.
Using the Chandrayaan-2 lunar orbiter, a team of researchers detected 1,400 slow-growing flares in three years, greatly increasing the catalog of slow flares from the around 100 that had been detected over the past 40 years of solar study.
Related: The Sun unleashes a monstrous X-class solar flare, the most powerful since 2017 (video)
“There was a consensus in the solar physics community, since the early 2000s, that most solar flares are rapidly increasing intensities, followed by a slow decay,” said Aravind Bharathi Valluvan, team leader and student graduated in astrophysics from the University of California. San Diego, told Space.com. “However, what my research, along with that of my team, has shown is that not all solar flares follow that pattern.”
Valluvan explained that the solar science community had overlooked slower-growing flares, or “hot thermal” flares, because computer algorithms used to detect solar flares in observational data have focused on fast-growing, or “impulsive” flares. “. Impulsive flares are defined as those that cover the maximum possible area in less than half their lifetime.
“We didn’t do that, but rather took a more general approach. What we saw is that there are many more slow-growing flares, and it’s not an insignificant subset. In fact, they make up a quarter of all flares,” they said. continued. “Therefore, we need to study hot thermal flares as a separate population. Currently, our understanding of these types of slower flares is quite limited.”
What makes slow-growing flares a mystery?
Slow-growing flares are something of a mystery because the magnetic reconnection process that is believed to generate both impulsive flares and hot thermal flares is rapid, which should also result in a rapid release of energy.
Valluvan explained that solar scientists need to better understand the precise way slow-growing flares are generated, how they propagate through the solar corona (the Sun’s outer atmosphere), and whether this propagation mechanism can lead to a larger manifestation. slow.
One clue may lie in something very contradictory about these slower flares: the fact that they are incredibly hot.
Rapidly rising impulsive flares are associated with temperatures of around 18 million degrees Fahrenheit (10 million degrees Celsius). But slow-growing flares are nicknamed “hot thermal flares” because they are associated with even higher temperatures, up to 54 million degrees Fahrenheit (30 million degrees Celsius).
“One thing for sure is that the solar atmosphere is a very violent place. There’s a lot of turbulent activity, a lot of magnetic fields of fluid plasma mixing there, so there’s a lot of turbulence,” Valluvan said. “Impulsive solar flares are associated with a non-thermal energy injection process. Turbulent activity causes this non-thermal injection.”
Valluvan suggested that there might be a less turbulence-dependent and more thermal and magnetic process behind the generation of slow-growing flares.
Another significant result of this research is that there are no intermediate flares between fast-growing impulsive flares and slower hot thermal flares. There must be some reason why flares only occur at one of two extremes.
“What is this kind of equilibrium generating process that’s going on?” Valluvan said. “That’s something I’ve been looking into.”
Ultimately, solving the mystery of slow-growing solar flares may help scientists solve a long-standing puzzle: why is the solar corona hotter than the sun’s “surface,” or photosphere?
The corona is hundreds of times hotter than the sun’s surface even though the photosphere is closer to the sun’s heat source, the nuclear fusion processes that occur in its core. This has worried scientists for about half a century.
“Why is the atmosphere hotter than the surface of the Sun? This is something that has always been proposed as a solution to solar flares, but we have never found evidence of it,” Valluvan concluded. “These new types of flashes could be a possible resolution to this mystery of coronal heating. And that’s one of the things I’m most excited about.”
The research was published in January in the journal Solar Physics.