Astronomers utilizing a visible broadband imager at NSF’s Daniel K. Inouye Solar Telescope captured an extraordinary coronal loop strand during the attenuation phase of the X1.3 class flare on August 8, 2024. This discovery heralds a significant advancement in determining the fundamental scale of solar coronal loops, advancing flare modeling into a groundbreaking territory.
High-resolution image of flares from the Inouye Solar Telescope, taken at 8:12 UT on August 2024. The image shows approximately four earth diamonds on each side. Labels for various related regions of the image are added to clarify: flare ribbons (bright regions of energy emissions in the dense low solar atmosphere) and arcades of coronal loops (arcs of magnetic field lines that transport energy from the corona to the flare ribbons). Image credit: NSF/NSO/AURA.
Coronal loops are plasma arches that follow solar magnetic field lines and often precede solar flares, which release massive amounts of energy tied to some of these lines.
This energy burst ignites solar storms that can impact Earth’s vital infrastructure.
Inouye astronomers observe sunlight at the H-Alpha wavelength (656.28 nm) to reveal specific solar features that remain hidden in other forms of solar observation.
“A lot of effort has gone into understanding this domain,” noted Dr. Cole Tamburi, an astronomer from the University of Colorado, Boulder.
“These flares represent some of the most energetic occurrences in our stars, and we were fortunate to capture this under ideal observational conditions.”
Dr. Tamburi and his team concentrated on the thin magnetic field loops resembling razors, woven over the flared ribbons.
On average, the loops measured around 48 km in width, although some results were limited by the telescope’s resolution.
“Before Inouye, I could only envision what this scale might look like,” remarked Dr. Tamburi.
“Now we can witness it in reality. These are the tiniest coronal loops observed on the sun.”
Inouye’s Visible Broadband Imager (VBI) tuned to the H-Alpha filter can resolve features down to 24 km.
This resolution is more than twice as sharp as that of the next best solar telescope, making this discovery possible.
“It’s one thing to theorize about a telescope’s capabilities,” commented Dr. Maria Kazachenko, PhD, from the University of Colorado Boulder.
“It’s invigorating to see those theories validated in practice.”
Initially, the research plan involved investigating the dynamics of chromospheric spectral lines using Inouye’s Visible Spectrometer (VISP). However, VBI data uncovered an unexpected treasure: an intricate coronal structure that can directly enhance flare models built with complex radiative hydrodynamic codes.
“We set out to find one thing and stumbled upon something even more intriguing,” Dr. Kazachenko stated.
The prevailing theory suggested that coronal loops could range from 10 to 100 km in width, but verifying this observationally had been challenging.
“We are finally gaining insight into the spatial scales we have long speculated about,” Dr. Tamburi explained.
“This paves the way for examining not just size, but shape, evolution, and even the scales where magnetic reconnection—the engine behind flares—occurs.”
Perhaps the most exciting implication is that these loops might be fundamental structures, core components of flare architecture.
“In that scenario, we wouldn’t just be mapping out clusters of loops; for the first time, we’re analyzing individual loops,” Dr. Tamburi added.
“It’s akin to observing a forest and suddenly recognizing all the trees.”
The image itself is stunning. A radiant arcade crowned with dark, thread-like loops, vibrant flared ribbons marked with strikingly sharp contours—ascending triangular patterns near the center and arc-shaped formations at the top.
“Even casual observers will soon recognize its complexity,” Dr. Tamburi remarked.
“This represents a landmark moment in solar science.”
“We are finally observing the sun at a scale that makes sense.”
The team’s paper will be published in Astrophysics Journal Letters.
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Cole A. Tumburi et al. 2025. Revealing unprecedented microstructure in coronal flare loops using DKIST. apjl in press; doi: 10.3847/2041-8213/ADF95E
Source: www.sci.news
