You’ve heard of sunspots, but how about Sun dots? A recent solar mission has snapped photos of tiny, bright dots on the Sun, and astronomers are contemplating their cause.
Something New on the Sun
Today’s article dives into some of the exquisite data from Solar Orbiter to investigate an even smaller-scale phenomenon: the fleeting appearance of dozens of tiny, bright dots.
A team led by Sanjiv Tiwari (Lockheed Martin Solar and Astrophysics Laboratory and Bay Area Environmental Research Institute) began their investigation of these dots with Solar Orbiter observations from 20 May 2020, when the Sun’s dynamic activity cycle was at a simmer. Using images from the Extreme Ultraviolet Imager, Tiwari and collaborators analyzed a region where loops and strands of magnetic flux were poking through the Sun’s surface. The images revealed tiny spots faintly visible against the bright background of hot plasma.
Making a Magnetic Connection
The team also analyzed images and magnetic field measurements from the Solar Dynamics Observatory, a spacecraft that surveys the Sun from Earth orbit. (The team noted that any features that pop up in the Solar Orbiter images do so 3.22 minutes before they appear in the Solar Dynamics Observatory images due to the time it takes light to travel between the two spacecraft.) The magnetic field measurements revealed that the dots tended to be concentrated in areas with strong magnetic fields or regions where inward- and outward-pointing magnetic field lines are found close together.
So, what causes these dots? Using magnetohydrodynamic simulations, the team confirmed that most dots are associated with interacting magnetic field lines and potentially occur when field lines snaking out from beneath the solar surface connect with those already above the surface. However, a smaller number of dots were free of tangled magnetic field lines, and they may have instead been formed by shock waves moving through the region.
With Solar Orbiter making its way closer to the Sun over the next few years, we should be able to get a better view of these dots and better understand their origins. Who knows what kind of dots we’ll be able to spot then!
“SolO/EUI Observations of Ubiquitous Fine-scale Bright Dots in an Emerging Flux Region: Comparison with a Bifrost MHD Simulation,” Sanjiv K. Tiwari et al 2022 ApJ 929 103. doi:10.3847/1538-4357/ac5d46
This post originally appeared on AAS Nova, which features research highlights from the journals of the American Astronomical Society.