Scientists have discovered a signal coming from the Sun’s atmosphere that has a pattern similar to a heartbeat. An international team of researchers has written about this in a journal called Nature Communications. The signal was found coming from a C-class solar flare, which is over 5,000 kilometers above the surface of the Sun.
Scientists think that the results of this study may help them understand where solar flares — the strongest explosions in our solar system — come from.
Sijie Yu, an astronomer from the Center for Solar-Terrestrial Research said that they just made a mysterious and unexpected discovery. They found out that during powerful events on the Sun, there was a repeated pattern of energy being released and then dissipated in its atmosphere. Scientists have not been able to solve the mystery behind this repeated pattern called “quasi-periodic pulsations”.
Solar radio bursts are powerful bursts of radio waves that come from the Sun and usually happen together with solar flares. Scientists have seen signals with repeating patterns coming out of these events in the past. Recently, a team studied a solar flare event using the NJIT’s Expanded Owens Valley Solar Array (EOVSA) telescope located near Big Pine, California, and they figured out what causes these pattern signals.
The Expanded Owens Valley Solar Array (EOVSA) observes the Sun by detecting radiation across a broad range of microwave frequencies, between 1 and 18 gigahertz. This radiation is caused by energetic electrons in the Sun’s atmosphere which are triggered during flares.
Using EOVSA, scientists have noticed a special pattern in the flare’s radio waves – it’s like a “heartbeat”, repeating every 10 to 20 seconds! The lead scientist who made this discovery is Yuankun Kou, a Ph.D. student from Nanjing University (NJU).
The research team noticed a regular type of pulsing that was happening over 25,000 kilometers inside the eruption’s center – where different types of magnetic field directions meet and cause lots of energy to be released. Then, they were surprised to find out there was also a second ‘heartbeat’ in the same area!
Kou said that repeating patterns for solar radio bursts are usually normal but they found something extra. They found a second source which has a similar pattern as the first one and it’s located along the current sheet.
Yu explained that this was the first time scientists were able to detect a special repeating radio signal near a place called the ‘flare current sheet’. EOVSA’s special microwave equipment can measure the energy from two sources which help scientists discover which one caused the other.
The experts used what’s called EOVSA spectral imaging to analyze high energy particles during the flare. This revealed that the distribution of these particles at a main source changed in phase with another source found in an electronic current sheet. This could mean that both places are related, according to Bin Chen from NJIT and one of the people on the research team.
The research team did some 2.5D numerical modelling of a solar flare, which was headed by one of the scientists on the paper. To check their finding, they made use of an observation satellite called ‘GOES’ from NOAA to measure two different types of rays coming from the sun’s atmosphere.
Cheng asked, “Why does the current sheet have regular patterns? What’s making these patterns and how is it connected to the formation of QPPs?”
The researchers investigated and found that there are like bubbles forming in the current sheet, which move close to the flaring part in a not-quite-regular way.
According to Cheng, magnetic islands in the current sheet are an important factor that affects the amount of energy released during eruptions. This periodic releasing of energy creates high-energy electrons which can be seen as bursts of light in microwaves and X-rays. Yu believes this research sheds some new insight on what causes these explosive events.
Scientists have figured out that the energy fluctuations called “Quasi-Periodic Pulses” (QPPs) during Solar Flares are caused by regular reconnections in the area where energy is released. This new information has changed what we thought about previous Solar Flares, and they need to be looked at differently now.
The study written by Yuankun Kou, Xin Cheng, Yulei Wang, Sijie Yu, Bin Chen, Eduard P. Kontar and Mingde Ding called “Microwave imaging of quasi-periodic pulsations at flare current sheet” will be published in Nature Communications on December 12th 2022. This research was funded by the National Science Foundation.
