Tadpole-like jets could help explain why the sun's corona is so hot

Feb. 20 (UPI) -- Researchers have discovered a novel type of solar jet that could help solve the mystery of the sun's super hot corona.

The sun's corona, the swirling upper atmosphere, is more than 200 times hotter than the sun's furnace, and for decades, scientists have struggled to understand why.

The new jets are tadpole-shaped and found extending from solar regions that feature intense magnetic fields. Scientists previously called tadpole-shaped jets "pseudo-shocks."

Researchers first noticed the jets while studying observations by NASA's Interface Region Imaging Spectrograph, or IRIS. The jets were imaged protruding from sunspots and stretching 3,000 miles into the corona. Like tadpoles, the jets feature a bulky head and thin tail.

Previously, astrophysicists have proposed nanoflares and electromagnetic waves as explanations for the corona's intense heat.

Nanoflares form when the chaotic, swirling magnetic field lines break up and then violently reconnect. The explosive force of the reconnection produces a surge of high-energy plasma particles. Some scientists argue these explosions supply the sun's upper atmosphere with extremely hot, super-charged particles.

Other researchers contend a type of electromagnetic wave called Alfvén waves help carry hot, super-charged particles into the corona.

Most scientists now agree that some combination of nanoflares, Alfvén waves and other electromagnetic phenomena combine to superheat the sun's upper atmosphere. Tadpole-like jets, researchers contend in a newly published Nature Astronomy paper, are one the "other phenomena."

Like related phenomena, including sunspots, solar flares and coronal mass ejections, scientists estimate tadpole-like jets increase in frequency during the more active periods of the sun's 11-year cycle.

"We were looking for waves and plasma ejecta, but instead, we noticed these dynamical pseudo-shocks, like disconnected plasma jets, that are not like real shocks but highly energetic to fulfill the sun's radiative losses," lead study author Abhishek Srivastava, scientist at the Indian Institute of Technology, said in a news release.

Researchers predict the jets are triggered magnetic reconnection, similar to the way nanoflares form. Using IRIS data, scientists built a computer model of the tadpole-like jets. Simulations showed the pseudo shocks deliver enough high-energy plasma to heat the inner corona.

For future studies, IRIS observations could be coupled with measurements made by NASA's Parker Solar Probe to produce a more detailed picture of the tadpole-like jets underlying physical processes.