Solar radio bursts similar to 'heartbeats' discovered

According to a new study, a solar radio burst with a signal pattern similar to that of a heartbeat.

An international team of researchers discovered the origin of a radio signal from a class C solar flare to more than 5,000 kilometers above the surface of the Sun, according to results published in the journal Nature Communications.

“The discovery is unexpected”, says Sijie Yu, corresponding author of the study and an astronomer affiliated with NJIT’s Center for Solar-Terrestrial Research.

“This heartbeat pattern is important for understanding how energy is released and dissipated in the sun’s atmosphere during these incredibly powerful explosions on the Sun. However, the origin of these repeating patterns, also called quasi-periodic pulsations, has long been a mystery and a source of debate among solar physicists.”

Solar radio bursts are intense bursts of radio waves from the Sun, They are often associated with solar flares and are known to present signals with repetitive patterns.

The team was able to discover the source of these pattern signals after study microwave observations of a solar flare event on July 13, 2017, captured by NJIT’s Expanded Owens Valley Solar Array (EOVSA) radio telescope at the Owens Valley Radio Observatory (OVRO), California.

EOVSA routinely observes the Sun in a wide range of microwave frequencies from 1 to 18 gigahertz (GHz) and it is sensitive to radio radiation emitted by high-energy electrons in the Sun’s atmosphere, which are energized in solar flares.

According to Yuankun Kou, lead author of the study and a PhD student at Nanjing University (NJU), observations of the eruption by EOVSA revealed radio bursts with a signal pattern that was repeated every 10-20 seconds, “like a heartbeat”.

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The team identified a strong quasi-periodic pulsation (QPP) signal at the base of the electrical current sheet. which extends more than 25,000 kilometers through the core region of the eruption, where opposing magnetic field lines approach, break, and reconnect, generating intense energy that fuels the flare.

But surprisingly, Kou says that they discovered a second heartbeat in the flare.

“Repeating patterns are not uncommon in solar radio flares,” Kou explains. “But interestingly, there is a secondary source that we did not expect located along the stretched current sheet that pulsates in a similar way to the main QPP source.”

“The signals probably originate from quasi-repetitive magnetic reconnections in the flare’s current sheet,” Yu added. “It is the first time that a quasi-periodic radio signal located in the reconnection region has been detected. This detection can help us determine which of the two sources caused the other.”

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