A team of scientists funded by NASA has made a remarkable discovery – long-lasting radio signals emanating from sunspots. Sunspots are regions on the Sun’s surface where the magnetic field is incredibly strong, causing a decrease in surface temperatures and atmospheric pressure. This creates dark spots on the solar surface. The team’s findings demonstrate that the radio signals are similar to the auroras observed on Earth. These signals were detected approximately 40,000 kilometers above a sunspot, marking the first time they have been observed on the Sun. Previous long-lasting radio signals had only been observed on other planets or stars.

Lead author Sijie Yu from the New Jersey Institute of Technology referred to this finding as the “first detection of its kind.” The discovery of these long-lasting radio signals at the Sun not only aids in understanding our own star, but it also provides insight into the functionality of distant stars. By learning more about the processes behind the radio signals and how they are produced, scientists can gain a deeper understanding of the universe.

Normally, the Sun emits short radio bursts that typically last only a few minutes to a few hours. However, the radio bursts observed by Yu and his team lasted for over a week, which is significantly longer than the Sun’s usual short radio bursts. The observations were conducted using the Karl G. Jansky Very Large Array (VLA) in New Mexico.

These long-lasting radio bursts also possess spectra and polarization characteristics that resemble the auroras produced by Earth’s atmosphere and magnetic field. On Earth, auroras are generated by the interaction between solar particles and the magnetic field. When solar particles are pulled and accelerated toward the poles where magnetic field lines converge, they produce intense radio signals at frequencies of a few hundred kilohertz. Eventually, when these solar particles reach the atmosphere, they collide with atoms and emit light, resulting in an aurora.

After analyzing the data collected with VLA, Yu and his team found that the sunspot radio bursts are likely produced through a process similar to the production of auroras. Energetic electrons become trapped within the magnetic field emitted from the sunspot. Once captured in the field, these particles are pulled and accelerated downward to the sunspot, where the magnetic field lines converge. This process generates radio signals.

Unlike Earth, Jupiter, and Saturn’s auroras, however, the sunspot radio bursts occur at much higher frequencies of approximately one million kilohertz. This substantial leap in frequency is due to the sunspot’s magnetic field being thousands of times stronger than Earth’s.

Interestingly, these long-lasting radio bursts have also been observed on several different planets as well as on certain types of low-mass stars. The discovery of these bursts at the Sun suggests that large starspots may also emit aurora-like radio emissions, much like the polar regions of stars.

Yu expressed excitement over this discovery, as it challenges existing notions of solar radio phenomena and opens up new avenues for exploring magnetic activities in our own Sun and in distant stellar systems. In the coming weeks and months, Yu and his team plan to re-investigate other solar radio bursts to determine if any resemble the long-lasting bursts discovered with VLA. They aim to establish if some of the previously recorded solar bursts could be instances of this newly identified emission.

Heliophysicist and solar radio researcher Natchimuthuk Gopalswamy of NASA’s Goddard Space Flight Center believes that NASA’s heliophysics fleet is well-suited for further investigation into the source regions of these radio bursts. For example, the Solar Dynamics Observatory continually monitors the Sun’s active regions, which are likely responsible for generating this phenomenon.

The discovery of long-lasting radio bursts above sunspots marks a significant advancement in solar research. It provides invaluable insights into the workings of our own star as well as distant stellar systems. This new understanding not only enhances our understanding of the universe but also opens up possibilities for further research in magnetism and solar radio phenomena. Exciting times lie ahead as scientists continue to explore and unravel the mysteries of our dynamic Sun.