Universe Today
Getting close to things is one way for scientists to collect better data about them. But that's been hard to do for the Sun, since getting close to it typically entails getting burnt to a crisp. Just ask Icarus. But if Icarus had survived his close encounter with the Sun, he might have been able to see massive magnetic “tadpoles” tens of thousands of kilometers wide reconnecting back down to the surface of our star. Or maybe not, because he had human eyes, not the exceptionally sensitive Wide-Field imagers the Parker Solar Probe used to look at the Sun while it made its closest ever pass to our closest star. A new paper in The Astrophysical Journal Letters from Angelos Vourlidas of Johns Hopkins University’s Applied Physics Laboratory and his co-authors describes what they say on humanity’s closest brush with the Sun so far.
Parker actually made that pass, which was still about 4 million miles away from the Sun itself, in December 2024, it’s 22nd such perihelion of its mission. While that may seem far, in astronomical terms it’s basically touching the Sun itself, and is technically considered inside the Sun’s atmosphere. Which allowed the probe’s cameras to capture magnetic explosions happening essentially right in front of it.
There were three big discoveries described in the paper. First was the confirmation of “tadpoles”. That term is used to describe dark, tiny shapes that astronomers could barely make out in magnetic loops that appeared to be swimming back toward the Sun. They are actually parts of a magnetic loop that “breaks”, and sends part of the energy back towards the Sun (the head of the tadpole) while other parts are sent off into space, creating a void that looks like the tadpole’s tail.
Video from NASA showing how the magnetic fields in the corona are moving. Credit - NASA Goddard YouTube ChannelLong theorized, this is the first time any instrument has picked up these magnetic “inflow swarms” as they’re also called, in any sort of resolution. Some of them were small enough to not even be detected from Earth. Though “small” in the context of solar astronomy means that they were still about twice the diameter of the Earth. Solar physicists believe these inflow swarms play a critical part in dictating where and how solar storms happen, so they plan to keep an eye on them given the potential impact they have on Earth’s space weather.
Another new heliophysics feature was the ripping of what plasma scientists call the Heliospheric Current Sheet (HCS). It’s an electrical sheet that separates the north and south magnetic fields of the Sun. While it looks like a sheet in electrical terms, its physical manifestation is simply in a series of magnetic field lines rather than fabric. But still, scientists got to watch as part of it was stretched, started to shake, and then ripped apart.
This action is known as the “tearing-mode instability”, and mimics how a flag would react in a hurricane. When a solar storm squeezed the sheet, it broke into separate pieces. Scientists have often simulated this phenomena, but very rarely actually observed it, so seeing it up close with Parker was a milestone. One interesting feature was that it grew a massive “tadpole” that at one point was expanding at 5,000 km/minute for over two hours - expanding in size by over 185 before it disappeared.
NASA video showcasing Parker's orbit. Credit - NASA Goddard YouTube ChannelBut perhaps the most intriguing discovery was the third - observing the “birth” of in/out pairs. Parker watched as a single magnetic structure in the Sun’s corona was “pinched” in the middle and separated into two separate blogs. One was pulled back into the Sun, while the other shot away from the Sun absurdly quickly. They estimated its speed at 560 km/s, which is much faster than models predicted.
This “pinch off” process is a key player in the creation of solar storms, as scientists theorize it’s what sends many of the potentially hazardous particles our way during coronal mass ejections (CMEs). Capturing a detailed image of the process for the first time is invaluable for heliophysicists updating their models of the Sun. And it sounds like they’ll certainly have to in order to reflect the increased speed of the one Parker observed.
Luckily, Parker is not done yet either. Its primary mission officially ended in June, but it will continue doing laps around the run, reaching perihelion of about the same distance about 4 times a year. That is until it runs out of fuel, and, unlike Icarus, burns up in the Sun itself. But in so doing, it will have brought the most vivid pictures of our solar neighbor that we’re ever had. That seems like a worthy legacy, though it doesn’t serve as an allegory for human hubris - more like a paean to human ingenuity.
Learn More:
NASA - NASA’s Parker Solar Probe Spies Solar Wind ‘U-Turn’
A. Vourlidas et al - High-resolution Imaging of the Magnetic Reconfiguration of the Corona from inside the Corona by WISPR on Parker Solar Probe
UT - NASA's Parker Solar Probe Makes its Record-Breaking Closest Approach to the Sun
