NASA's SDO sees new kind of magnetic explosion on sun

December 17, 2019

NASA's Solar Dynamics Observatory has observed a magnetic explosion the likes of which have never been seen before. In the scorching upper reaches of the Sun's atmosphere, a prominence -- a large loop of material launched by an eruption on the solar surface -- started falling back to the surface of the Sun. But before it could make it, the prominence ran into a snarl of magnetic field lines, sparking a magnetic explosion.

Scientists have previously seen the explosive snap and realignment of tangled magnetic field lines on the Sun -- a process known as magnetic reconnection -- but never one that had been triggered by a nearby eruption. The observation, which confirms a decade-old theory, may help scientists understand a key mystery about the Sun's atmosphere, better predict space weather, and may also lead to breakthroughs in the controlled fusion and lab plasma experiments.

"This was the first observation of an external driver of magnetic reconnection," said Abhishek Srivastava, solar scientist at Indian Institute of Technology (BHU), in Varanasi, India. "This could be very useful for understanding other systems. For example, Earth's and planetary magnetospheres, other magnetized plasma sources, including experiments at laboratory scales where plasma is highly diffusive and very hard to control."

Previously a type of magnetic reconnection known as spontaneous reconnection has been seen, both on the Sun and around Earth. But this new explosion-driven type -- called forced reconnection -- had never been seen directly, thought it was first theorized 15 years ago. The new observations have just been published in the Astrophysical Journal.

The previously-observed spontaneous reconnection requires a region with just the right conditions -- such as having a thin sheet of ionized gas, or plasma, that only weakly conducts electric current -- in order to occur. The new type, forced reconnection, can happen in a wider range of places, such as in plasma that has even lower resistance to conducting an electric current. However, it can only occur if there is some type of eruption to trigger it. The eruption squeezes the plasma and magnetic fields, causing them to reconnect.

While the Sun's jumble of magnetic field lines are invisible, they nonetheless affect the material around them -- a soup of ultra-hot charged particles known as plasma. The scientists were able to study this plasma using observations from NASA's Solar Dynamics Observatory, or SDO, looking specifically at a wavelength of light showing particles heated 1-2 million kelvins (1.8-3.6 million F).

The observations allowed them to directly see the forced reconnection event for the first time in the solar corona -- the Sun's uppermost atmospheric layer. In a series of images taken over an hour, a prominence in the corona could be seen falling back into the photosphere. En route, the prominence ran into a snarl of magnetic field lines, causing them to reconnect in a distinct X shape.

Spontaneous reconnection offers one explanation for how hot the solar atmosphere is -- mysteriously, the corona is millions of degrees hotter than lower atmospheric layers, a conundrum that has led solar scientists for decades to search for what mechanism is driving that heat. The scientists looked at multiple ultraviolet wavelengths to calculate the temperature of the plasma during and following the reconnection event. The data showed that the prominence, which was fairly cool relative to the blistering corona, gained heat after the event. This suggests forced reconnection might be one way the corona is heated locally. Spontaneous reconnection also can heat plasma, but forced reconnection seems to be a much more effective heater -- raising the temperature of the plasma quicker, higher, and in a more controlled manner.

While a prominence was the driver behind this reconnection event, other solar eruptions like flares and coronal mass ejections, could also cause forced reconnection. Since these eruptions drive space weather -- the bursts of solar radiation that can damage satellites around Earth -- understanding forced reconnection can help modelers better predict when disruptive high-energy charged particles might come speeding at Earth.

Understanding how magnetic reconnection can be forced in a controlled way may also help plasma physicists reproduce reconnection in the lab. This is ultimately useful in the field of laboratory plasma to control and stabilize them.

The scientists are continuing to look for more forced reconnection events. With more observations they can begin to understand the mechanics behind the reconnection and often it might happen.

"Our thought is that forced reconnection is everywhere," Srivastava said. "But we have to continue to observe it, to quantify it, if we want prove that."

NASA/Goddard Space Flight Center

Related Plasma Articles from Brightsurf:

Plasma treatments quickly kill coronavirus on surfaces
Researchers from UCLA believe using plasma could promise a significant breakthrough in the fight against the spread of COVID-19.

Fighting pandemics with plasma
Scientists have long known that ionized gases can kill pathogenic bacteria, viruses, and some fungi.

Topological waves may help in understanding plasma systems
A research team has predicted the presence of 'topologically protected' electromagnetic waves that propagate on the surface of plasmas, which may help in designing new plasma systems like fusion reactors.

Plasma electrons can be used to produce metallic films
Computers, mobile phones and all other electronic devices contain thousands of transistors, linked together by thin films of metal.

Plasma-driven biocatalysis
Compared with traditional chemical methods, enzyme catalysis has numerous advantages.

How bacteria protect themselves from plasma treatment
Considering the ever-growing percentage of bacteria that are resistant to antibiotics, interest in medical use of plasma is increasing.

A breakthrough in the study of laser/plasma interactions
Researchers from Lawrence Berkeley National Laboratory and CEA Saclay have developed a particle-in-cell simulation tool that is enabling cutting-edge simulations of laser/plasma coupling mechanisms.

Researchers turn liquid metal into a plasma
For the first time, researchers at the University of Rochester's Laboratory for Laser Energetics (LLE) have found a way to turn a liquid metal into a plasma and to observe the temperature where a liquid under high-density conditions crosses over to a plasma state.

How black holes power plasma jets
Cosmic robbery powers the jets streaming from a black hole, new simulations reveal.

Give it the plasma treatment: strong adhesion without adhesives
A Japanese research team at Osaka University used plasma treatment to make fluoropolymers and silicone resin adhere without any adhesives.

Read More: Plasma News and Plasma Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to