Indeed, there are many strange things connected with the sun, but a leading space probe just gave us a hint that we might need to solve one of them.
New observations from the European Space Agency’s (ESA) Solar Orbiter show that the constant reconnection of small magnetic field lines may be at least one reason why some parts of the Sun are warmer than others.
The problem is that the temperature of the Sun’s surface is about 5500 degrees Celsius (9932 Fahrenheit) – the normal temperature for a sun-like star. But matter in its atmosphere only gets hotter the further away from the surface, peaking at 2 million degrees Celsius in the highest regions known as the corona.
We’ve known about this coronal temperature inversion since the 1940s, and it’s thought to be a common feature of stars. But what scientists haven’t been able to pinpoint is the cause. One possible solution is continuous magnetic reconnection on a small scale.
At least on a large scale, magnetic reconnection is a well-documented behavior of the Sun. Most stars are turbulent balls of incredibly hot plasma. A fluid composed of charged particles interacts strongly with electromagnetic forces. This means that bodies like our Sun pulsate positively with highly complex and chaotic magnetic fields. Beyond the innermost layer of the Sun’s atmosphere, known as its photosphere, these magnetic field lines can intertwine, stretch, trap, and reconnect.
This produces a massive burst of energy—the engine that powers solar flares and coronal mass ejections that send particles through the solar system.
On a smaller scale, scientists thought, these reconnection events would pump energy into the corona, thereby providing it with a heating source. But the sun is so bright and hot that it is difficult to see it; We simply did not have enough resolution to see the small scales on which this process will take place.
And this is where Solar Orbiter comes into play. Launched in February 2020, the European Space Agency’s (ESA) solar probe is approaching our star, approaching dangerous close-ups in a series of repeated encounters to study its activity in stunning detail.
When the spacecraft made its first approach, it noticed something startling. On March 3, 2022, ultra-high-resolution images in the intense ultraviolet wavelengths showed that magnetic reconnection is occurring on very small scales—only 390 kilometers (242 miles) across.
It’s really incredible. Scientists managed to unravel and study the phenomenon, a little less than the length of the “Grand Canyon” on the surface of the Sun.
Within an hour, the spacecraft recorded a point, known as the null point, where the magnetic field strength drops to zero. This is the magnetic reconnection point. During this time, the zero point temperature was maintained at about 10 million degrees Celsius. At point-blank range, a continuous jet also formed, which flew away at a speed of about 80 kilometers per second, visible as “blobs” of plasma.
This is known as a “soft” reunion, but a more turbulent reunion phase is also shown point-blank. This reconnection process only lasted four minutes, but it showed that the two types of reconnection occurred simultaneously and on a smaller scale than we could previously determine.
These two types of reconnections would transfer mass and energy to the corona above them, providing a heat source that could explain at least some of the poorly understood temperature inversions.
The results also show that reconnection can occur at scales too small for Solar Orbiter’s resolution, at least at this close approximation. The next few images, in addition to the one just taken on April 10, will be zoomed in, which could lead to higher resolution observations.
Meanwhile, we have the first observational evidence that a stable small-scale magnetic reconnection is taking place on the surface of the Sun, confirming a long-standing hypothesis about how the corona heats up and bringing us closer to understanding how the corona heats up.
The study is published in the journal Nature Communications.
Source: Science Alert
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