Scientists have made a major breakthrough in solar energy observation by developing the first adaptive optical system capable of studying solar corona (the mysterious external atmosphere visible only in solar eclipse).
New “coronal adaptive optics” technology reveals previously unknown phenomena of corona, including twisted plasma flows that form and collapse in minutes while coronal raindrops are narrower than 20 kilometers. This advance, published in natural astronomy, promises to unravel the secrets of why corona burns millions of degrees while the sun’s surface remains relatively cool.
This achievement represents a quantum leap in solar physics, making resolution improvements nearly ten times the result of previous corona observations.
The time-lapse video captures the Sun’s prominence that has experienced a rapid, complex and turbulent reorganization, here promoted in unprecedented detail.
Break through atmospheric barriers
“Turbulence in the air can severely reduce images of objects in space, such as our sun, seen through telescopes. But we can correct it for this.”
Over the past two decades, adaptive optics have revolutionized observations of the solar surface by compensating for atmospheric blur. But these systems fail when pointing toward solar limbs beyond corona, where physics and many darkening functions require entirely new approaches.
The team’s solution involves the development of a specialized wavefront sensor that can track a faint hydrogen alpha structure in prominent and other coronal features. The sensor controls the mirror that is reshaped 2,200 times per second to offset atmospheric distortion.
Discover unknown
Within the first few days of operation, the system made the unexpected discovery, a distorted plasma flow that exhibited different behaviors from anything previously observed in solar physics.
“These are the most detailed observations to date, showing features that have not been observed before, and it’s not clear what they are,” said Vasyl Yurchyshyn, co-author of the study and NJIT-CSTR research professor. “These are the most detailed observations to date, showing us the sun that has never been seen before, and it’s not clear what they are,” Schmidt added. “Building an instrument is very exciting, showing us the sun that has never been seen before.”
The mysterious feature, which researchers call “coronary slurry”, is formed during the attenuation phase of the solar flare and exhibits twisted chains of less than 100 kilometers. The plasma flow moves at a speed of 55-90 kilometers per second, then suddenly stops and collapses in a collision, reminding the researchers of “a spiral galaxy with two arms.”
Coronal rainfall at the diffraction limit
The system also reveals new details about coronal rainfall—cooling plasma that condenses like precipitation in the Earth’s atmosphere and falls back to the surface of the sun.
“Rain droplets in the solar corona may be narrower than 20 kilometers,” NSO astronomer Thomas Schad concluded. “These findings provide new and valuable insights that are crucial for computer models of the coronary process.”
Observations show that about half of the coronal rain chains are narrower than 100 kilometers, and the structure extends to the telescope’s diffraction limit is 64 kilometers. This finding challenges current computer simulations and suggests that a three-dimensional effect may be necessary for accurate simulations of coronal rain formation.
Key technical achievements:
- Resolution improvement from over 1,000 km to 63 km
- Detect plasma stenosis to 20 kilometers
- Distorted coronary slurry found during flare decay
- Successfully tracked fast moving plasmas at 55-90 km/s
- First diffraction-limited observation of ground telescopes
Technical Challenges
“Adaptive optics are like pumped autofocus and optical image stabilization in smartphone cameras, but correct errors in the atmosphere rather than the user’s shaking hands,” said Nicolas Gorceix, optical engineer and chief observer of BBSO.
The technical barriers are huge. Unlike the surface of the sun, which provides rich bright features for tracking, Corona offers only sparse, dim structures scattered across vast areas. The team needs to develop new algorithms, optimize detector sensitivity, and solve complex calibration problems unique to non-LIMB observations.
A key detail is not covered extensively, involving complex flat field challenges that the team overcomes. Since hydrogen alpha light appears to be an absorption of the solar disk, but highlights the emission, the traditional calibration method completely fails. Researchers must use the protruding structure of diffusion as a calibration source to develop new technologies, a delicate process that requires precise matching of brightness levels and camera settings.
Impact on the coronavirus
The extreme temperatures of the corona (millions of degrees compared to the 6,000-degree surface of the sun) represent one of the biggest unsolved mysteries of solar physics. The new observations provide important clues about the underlying heating mechanism.
The distorted slurry found may represent direct evidence of the magnetic reconnection process that occurs in the current plate after solar flares. The features of the function—fast motion, twisted structure, kink instability and short life—are closely consistent with theoretical predictions of slurry produced during 3D magnetic reconnection.
These observations could help validate laboratory plasma experiments that exhibit the production of nanolorere in a braided magnetic ring, although the scales involved vary in order of magnitude.
Beyond the atmosphere of the earth
Achievement requires overcoming what scientists call “Anesian racism” – the way atmospheric turbulence changes with direction. This means that the wavefront sensor must use the actual coronal structure rather than the bright granulation pattern available on the sun’s surface.
“The new coronal adaptive optics close the decades of gap and provide images of coronal features at a resolution of 63 kilometers, the theoretical limit of the 1.6-meter-high Goode Solar telescope,” said Thomas Rimmele, chief technician at NSO.
The system achieves a strehl ratio between 20% and 40%, a measure of optical mass, which is sufficient to accommodate diffraction-limited observations when used in combination with post-processing techniques. This performance matches or exceeds the system used for solar surface observation.
Future applications
The team is already working to implement similar technologies on the 4-meter Daniel K. Inouye solar telescope in Hawaii, which will provide a more refined solution to the crown structure.
“This transformative technology could be adopted among global observers, and it promises to reshape ground-based solar astronomy,” said Philip R. Goode, a distinguished professor of physics research at NJIT-CSTR and former director of BBSO.
In addition to simple resolution improvements, the technology allows routine observations at previously impossible levels of quality. This consistency factor may be more valuable than peak performance, as it greatly increases the chance of capturing rare solar events at high resolution.
The researchers envision future developments, including laser guide systems, that can extend adaptive optical corrections even further into Corona, where natural features suitable for wavefront sensing become scarce.
What mystery will these new eyes reveal in the sun? Now, with coronary optics operating, solar physicists are expected to unlock secrets that have been hidden in atmospheric blur for decades. During the first operational period, the twisted slurry discovery suggests that in the external atmosphere of the sun’s overheated sun, there are more surprises waiting.
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