Detection of long-lasting aurora-like radio emission above a sunspot

TL;DR

This paper reports the detection of long-lasting, aurora-like radio emissions above a sunspot, providing insights into their origin and potential parallels with stellar auroral phenomena.

Contribution

It presents the first detailed analysis of solar radio bursts resembling auroral emissions, linking them to magnetic field structures and energetic electrons near sunspots.

Findings

Radio bursts are located above a sunspot with strong magnetic fields.

Emission characteristics are consistent with electron cyclotron maser (ECM) processes.

These solar bursts are weaker than similar emissions in low-mass stars.

Abstract

Auroral radio emissions in planetary magnetospheres typically feature highly polarized, intense radio bursts, usually attributed to electron cyclotron maser (ECM) emission from energetic electrons in the planetary polar region that features a converging magnetic field. Similar bursts have been observed in magnetically active low-mass stars and brown dwarfs, often prompting analogous interpretations. Here we report observations of long-lasting solar radio bursts with high brightness temperature, wide bandwidth, and high circular polarization fraction akin to these auroral/exo-auroral radio emissions, albeit two to three orders of magnitude weaker than those on certain low-mass stars. Spatially, spectrally, and temporally resolved analysis suggests that the source is located above a sunspot where a strong, converging magnetic field is present. The source morphology and frequency dispersion are consistent with ECM emission due to precipitating energetic electrons produced by recurring flares nearby. Our findings offer new insights into the origin of such intense solar radio bursts and may provide an alternative explanation for auroral-like radio emissions on other flare stars with large starspots.