Scientists uncover prolonged radio emissions above sunspot

A team of astronomers from New Jersey Institute of Technology's Center for Solar-Terrestrial Research (NJIT-CSTR) have uncovered prolonged radio emissions above a sunspot.

This extraordinary aurora-like display took place 40,000 km above a sunspot - a relatively dark and cold patch on the Sun. This emission, as the researchers said, is akin to the auroral radio emissions commonly seen in planetary magnetospheres such as those around Earth, Jupiter and Saturn, as well as certain low-mass stars.

Sijie Yu, the study's lead author and NJIT-CSTR scientist, said, "We've detected a peculiar type of long-lasting polarized radio bursts emanating from a sunspot, persisting for over a week. This is quite unlike the typical, transient solar radio bursts typically lasting minutes or hours. It's an exciting discovery that has the potential to alter our comprehension of stellar magnetic processes."

On Earth, this natural light show, called the Aurora Borealis or Aurora Australis, occurs in the polar regions as solar activities disturb the planet's magnetosphere, which facilitates the precipitation of charged particles to the polar region where the magnetic field converges, and interacts with oxygen and nitrogen atoms in the high atmosphere.

The novel solar radio emissions differ from previously known solar radio noise storms - both spectrally and temporally, according to the researchers.

"Our spatially, temporally and spatially resolved analysis suggests that they are due to the electron-cyclotron maser (ECM) emission, involving energetic electrons trapped within converging magnetic field geometries. However, unlike the Earth's auroras, these sunspot aurora emissions occur at frequencies ranging from hundreds of thousands of kHz to roughly 1 million kHz — a direct result of the sunspot's magnetic field being thousands of times stronger than Earth's," Yu explained.

"Our observations reveal that these radio bursts are not necessarily tied to the timing of solar flares either. Instead, sporadic flare activity in nearby active regions seems to pump energetic electrons into large-scale magnetic field loops anchored at the sunspot, which then power the ECM radio emission above the region," added Rohit Sharma, a scientist from the University of Applied Sciences Northwestern Switzerland (FHNW) and co-author of the study.

This discovery could have implications for astrophysicists to rethink their current models of stellar magnetic activity, the researchers said.