For the first time, astronomers were able to detect aurora signals that were fostered by electrons that accelerated through a sunspot over the surface of the Sun.
Solar Aurora?
The solar aurora happened around 40,000 kilometers over a sunspot, which is a dark patch on the solar surface that is magnetically warped. The radio wave bursts were detected by Earth astronomers over a week's course.
While astronomers were able to pick up aurora-like signals from other far stars, this is the first time that such a signal was observed from the Sun itself. The researchers noted their findings in the study "Detection of long-lasting aurora-like radio emission above a sunspot."
Astronomer Sijie Yu from the NJIT-CSTR (New Jersey Institute of Technology's Center for Solar-Terrestrial Research), the study's lead author, explains that the signal was quite unlike the usual transient radio bursts that usually go on for hours or minutes. Yu adds that the discovery is exciting and could potentially change current understanding of the magnetic processes stars undergo.
Is It the Same As Earth's Northern Lights?
Auroras on Earth result from energetic solar debris that zip across the atmosphere close to the poles, which is where the magnetic field is at its weakest. The debris also agitates molecules of nitrogen and oxygen. Because of this, the molecules are fostered to expel energy in light form and trace color curtain ripples through the sky.
The solar debris is usually released from the Sun when the magnetic fields that surround the sunspots knot before they spontaneously snap. Because of this, solar flares get released. Coronal mass ejections (CMEs), which are explosive solar material jets, also get expelled.
The solar aurora was detected by astronomers as they pointed a radio telescope towards a particular sunspot. The emission is believed to have resulted from solar flare electrons that were accelerated along the magnetic field lines of the sunspot that were powerful.
Yu explains that unlike the auroras observed on the Earth, the emissions observed over the sunspot take place at frequencies that go on from hundreds of thousands of kilohertz (kHz) to around a million kHz. This directly results from the magnetic field of the sunspot being a couple of thousand times stronger compared to that of the Earth's.
A Deeper Look Into the Sun
According to the researchers, this novel discovery could offer fresh ways to study solar activity. They have also started examining archival data in order to spot earlier hidden evidence of auroras on the Sun.
Solar physicist Surajit Mondal, who is a co-author from the study who is also from NJIT, explains that they are starting to piece the puzzle regarding how magnetic fields and energy particles interact in a system that has star spots that last long. Mondal adds that this is not just the case for the Sun but also for stars beyond the solar system.
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