Mysterious origin of ‘heartbeat-like’ radio bursts from Sun found

Astronomers have pinpointed the source of a mysterious radio burst from the Sun with a signal pattern similar to that of a “heartbeat” – an advance that sheds better light on the process behind solar flares.

The study, published on Tuesday in the journal Nature Communications, uncovered the source location of a radio signal coming from within a solar flare over 5,000km above the Sun’s surface.

Researchers, including those from the New Jersey Institute of Technology (NJIT) in the US, say the new findings can help us better understand the physical processes behind the energy release of solar flares.

Radiations from the Sun include intense bursts of radio waves associated with solar flares, and previous studies have found them to feature signals with repeating patterns.

“This beating pattern is important for understanding how energy is released and is dissipated in the Sun’s atmosphere during these incredibly powerful explosions on the Sun,” study co-author Sijie Yu from NJIT said in a statement.

“However, the origin of these repetitive patterns, also called quasi-periodic pulsations (QPP), has long been a mystery and a source of debate among solar physicists,” Dr Yu said.

Scientists made the discovery using data from a solar flare event on 13 July 2017 that was captured by NJIT’s radio telescope called the Expanded Owens Valley Solar Array (EOVSA).

The telescope observes the Sun in a wide range of frequencies and is sensitive to radio radiation emitted by high-energy electrons in the Sun’s atmosphere, which are energised in solar flares, researchers explained.

From the EOVSA observations, scientists found radio bursts with a signal pattern repeating every 10-20 seconds “like a heartbeat”, according to study lead author Yuankun Kou.

They found strong pulses at a region on the Sun, stretching over 25,000km through the solar flare eruption’s core region.

This region, scientists say, is where lines of magnetic field approach each other, break and reconnect and generate the intense energy powering the flare.

While such repeating patterns are not uncommon for solar radio bursts, researchers say they were surprised to find another source of the signals.

Scientists could then measure the energy spectrum of electrons at the two radio sources in this event.

They found that these signals originate from magnetic islands, or bubble-like structures on the Sun, which are almost periodically moving toward the flaring region.

The periodic process, the study found, leads to a repeating production of high-energy electrons that results in different kinds of radiation.

The findings, according to the researchers, shed more light on the process that drives explosive events in the Sun.