Instrument Helps Understand Mystery Of Sun’s Surface Temperature

Lee Rannals for – Your Universe Online

Scientists say they have solved a piece of the puzzle as to why the farther away you get from the surface of the Sun, the hotter you get.

The visible surface, or photosphere, on the Sun is 10,000 degrees Fahrenheit, but as you move away from it, you pass through a layer of hot, ionized gas or plasma called the corona. Scientists have been puzzled for a while about how the solar atmosphere can get hotter, rather than colder, the farther away you go from the Sun’s surface.

The High-resolution Coronal Imager (Hi-C) helped to reveal one of the mechanisms that pumps energy into the corona, heating it to temperatures up to 7 million degrees Fahrenheit. Researchers say the secret lies in a process known as magnetic reconnection.

“This is the first time we´ve had images at high enough resolution to directly observe magnetic reconnection,” said Smithsonian astronomer Leon Golub from Harvard-Smithsonian Center for Astrophysics. “We can see details in the corona five times finer than any other instrument.”

Heliophysicist Jonathan Cirtain from Marshall Space Flight Center said that the team developed an instrument capable of revolutionary image resolution of the solar atmosphere.

“Due to the level of activity, we were able to clearly focus on an active sunspot, thereby obtaining some remarkable images,” Cirtain added.

Magnetic fields help to power the Sun’s activity, such as solar flares and plasma eruptions. The surface of the sun is like a collection of a thousand-mile-long magnets, scattered around after bubbling up from inside the Sun.

These fields poke out of one spot and loop around to another spot, and plasma flows along those fields, outlining them with glowing threads.

Images from Hi-C have shown interweaved magnetic fields that were braided like hair. When those braids relax and straighten, they release energy, and the instrument was able to witness this during its flight.

Hi-C also detected an area where magnetic field lines crossed in an X, then straightened out as the fields reconnected, and a few minutes later, the spot erupted.

Energy bursts helped to boost the temperature of the corona to 7 million degrees Fahrenheit when the Sun is particularly active.

“We looked at one of the largest and most complicated active regions I´ve ever seen on the Sun,” said Golub. “We hoped that we would see something really new, and we weren´t disappointed.”

He said that data from Hi-C will continue to be analyzed for more insight, and that researchers are hunting for areas where other energy release processes were occurring.

Scientists hope to launch a satellite that could observe the Sun continuously in the future, at the same level of detail.

“We learned so much in just five minutes. Imagine what we could learn by watching the Sun 24/7 with this telescope,” Golub said in the release.

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