Astronomers Discover Unique Aurora-Like Emissions Above a Sunspot, Shifting Solar Science Paradigms
Astronomers from the New Jersey Institute of Technology's Center for Solar-Terrestrial Research have made a groundbreaking discovery: aurora-like emissions 40,000 km above a sunspot. This remarkable phenomenon, detailed in their recent study published in Nature Astronomy, shares characteristics with auroral emissions seen in planetary magnetospheres and certain low-mass stars. Unlike transient solar radio bursts, these long-lasting polarized radio bursts persisted for over a week, suggesting a new paradigm in our understanding of solar phenomena.
The discovery draws parallels with the famous auroral light shows on Earth, such as the Aurora Borealis and Aurora Australis. These Earthly displays occur when solar activities disturb the Earth's magnetosphere, precipitating charged particles that interact with atmospheric gases, resulting in visible light. The newly observed solar auroras, however, occur at much higher frequencies due to the sunspot's significantly stronger magnetic field.
Lead author Sijie Yu and his team observed these emissions over a vast sunspot region, noting their difference from known solar radio noise storms. The emissions are thought to be caused by the electron-cyclotron maser (ECM) emission, involving energetic electrons trapped within the sunspot's magnetic field. This discovery offers a local solar analog to study similar phenomena in other stars and planets.
Furthermore, these solar radio emissions are not necessarily tied to solar flares. Instead, flare activities in nearby regions may energize electrons that power the ECM radio emission above the sunspot. This 'sunspot radio aurora' exhibits a 'cosmic lighthouse effect,' rotating in sync with the solar rotation and creating a rotating beam of radio light.
This discovery has profound implications for astrophysics, providing insights into the behavior of our Sun and the magnetic activities of other stars. It challenges current models of stellar magnetic activity and helps understand signals from M-dwarfs, the most common star type in the universe.