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Observational Evidence of Solar Spicules Associated with Microfilament Eruptions Using DKIST

Using high-resolution H $\alpha$ observations from the DKIST, this study provides compelling evidence that solar spicules in quiet Sun regions are triggered by microfilament eruptions, identifying 30 such events and revealing distinct morphological classes of ejecta based on microfilament size.

Original authors: Qifan Dong, Xiaoli Yan, Zhike Xue, Liheng Yang, Jincheng Wang, Yadan Duan, Zhe Xu, Yian Zhou, Xinsheng Zhang, Zongyin Wu, Guotang Wu

Published 2026-06-17

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CC BY 4.0

Original authors: Qifan Dong, Xiaoli Yan, Zhike Xue, Liheng Yang, Jincheng Wang, Yadan Duan, Zhe Xu, Yian Zhou, Xinsheng Zhang, Zongyin Wu, Guotang Wu

Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine the Sun's surface not as a smooth, glowing ball, but as a chaotic, churning ocean of super-hot gas. Rising from this ocean are millions of tiny, fiery "whips" or "grass blades" called spicules. For over a century, scientists have wondered: What makes these things shoot up? Are they just random splashes, or is there a specific trigger?

This paper, using the world's most powerful solar telescope (the DKIST), finally caught the "trigger" in action. Here is the story of what they found, explained simply.

The Detective Work: A New Lens

Think of previous telescopes as looking at the Sun through a slightly foggy window. You could see the big waves, but the tiny ripples were blurry. The new DKIST telescope is like swapping that foggy window for a crystal-clear, high-definition lens. It allowed the scientists to see details on the Sun's surface that were previously invisible.

The Discovery: Tiny "Micro-Filaments"

The team watched a quiet patch of the Sun and spotted 30 specific events. In each event, they saw a tiny, dark, thread-like structure appear, twist, and then suddenly vanish. They call these micro-filaments.

The Analogy: Imagine a tiny rubber band sitting on a trampoline. Suddenly, it snaps or unravels. When it does, it shoots a jet of water (the spicule) straight up into the air.
The Size: These "rubber bands" were incredibly small—about 1,000 times smaller than the big solar filaments we usually see. Some were so tiny they looked like mere dots.

The Two Types of "Explosions"

The scientists noticed that the size of the tiny rubber band determined what kind of "jet" it created:

The Solo Shot: When the micro-filament was extremely small (the size of a dot), it triggered a single, sharp spicule. It was like a single, precise water jet shooting up.
The Cluster Blast: When the micro-filament was slightly larger, it triggered a bunch of spicules at once. It was like a sprinkler head spraying water in many directions.

The Twist: Spinning Jets

In about one-third of these events, the scientists saw the spicules twisting as they shot up, like a corkscrew.

The Analogy: Think of a tangled garden hose. When you untangle it quickly, the water doesn't just shoot straight; it spirals. The scientists believe the tiny magnetic "rubber bands" on the Sun were twisted, and when they snapped, they transferred that twist to the jet of gas, causing it to spin.

Why This Matters

For a long time, scientists had a theory that these tiny eruptions were the "missing link" explaining how mass and energy get from the Sun's lower atmosphere (chromosphere) up to its super-hot outer atmosphere (corona). But they lacked the proof because they couldn't see the tiny triggers.

This paper provides that proof. It shows that:

Spicules are not random: They are often triggered by the eruption of these tiny micro-filaments.
Everything is connected: The same physical process that creates giant solar storms and massive coronal jets also creates these tiny spicules; it's just a matter of scale. It's like how a massive ocean wave and a small ripple are both just water moving, just at different sizes.

The Bottom Line

Using the sharpest eyes we have ever had on the Sun, the researchers confirmed that tiny, snapping magnetic threads are the engines behind the Sun's fiery "grass blades." They found that the size of the thread determines whether you get a single jet or a spray of them, and that these tiny events happen constantly all over the Sun, acting as a massive conveyor belt for solar energy.

Technical Summary: Observational Evidence of Solar Spicules Associated with Microfilament Eruptions Using DKIST

Problem Statement
The formation mechanism of solar spicules remains a critical unsolved problem in solar physics, particularly regarding their role in transporting mass and energy from the chromosphere to the corona. While recent theoretical frameworks and observations of larger-scale coronal jets suggest a link to minifilament eruptions (MFEs), the hypothesis that spicules are driven by even smaller-scale "microfilament" eruptions has lacked definitive observational confirmation. Previous limitations in spatial resolution have prevented the clear identification of these sub-arcsecond structures and their direct causal relationship with individual spicule formation.

Methodology
This study utilizes high-resolution observations from the Daniel K. Inouye Solar Telescope (DKIST), specifically the Visible Broadband Imager (VBI) operating in the H $\alpha$ broadband passband (centered at 656.289 nm). Data were acquired from a quiet Sun region near the solar disk center on August 29, 2023, to minimize projection effects.

Data Processing: The VBI red channel provided images with a spatial sampling of 0.017 arcsec/pixel and a temporal cadence of 30 Hz. Speckle reconstruction was applied to 80-frame blocks, resulting in diffraction-limited images with an effective cadence of 2.667 seconds.
Magnetic Context: Photospheric magnetic fields were analyzed using SDO/HMI line-of-sight magnetograms (0.5 arcsec/pixel), while coronal responses were monitored via SDO/AIA 171 Å images.
Analysis: The authors manually identified and tracked 30 spicule events. Geometric parameters (length, width, duration) were extracted via Gaussian fitting of intensity profiles and manual tracking. Transverse and ejection velocities were estimated using space-time diagrams and Euclidean displacement measurements.

Key Contributions and Results
The study identifies 30 spicule events triggered by microfilament eruptions, providing the first direct observational evidence linking these specific small-scale structures to spicule formation.

Microfilament Characteristics: The detected microfilaments exhibit an average length of $0.93 \pm 0.46$ Mm, with a minimum length of 0.17 Mm. These dimensions are substantially smaller than previously reported minifilaments (typically 3–20 Mm) and align with the lower end of the power-law distribution of solar eruptive features proposed by Sterling & Moore (2016). The mean duration was $3.48 \pm 1.51$ minutes.
Morphological Classification: The authors identify two distinct morphological outcomes based on the scale of the erupting microfilament:
1. Individual Spicules: Associated with extremely small microfilaments (lengths $\lesssim 0.4$ Mm, averaging 0.24 Mm for the smallest cases). These events produce single, narrow plasma jets.
2. Enhanced Spicular Activities: Associated with larger microfilaments (lengths $\sim 0.7$ Mm), resulting in clusters of spicules.
Kinematics and Dynamics:
- Transverse Motion: 11 of the 30 events exhibited clear transverse/torsional motions with an average velocity of $15.91 \pm 7.00$ km s $^{-1}$ . This is interpreted as the transfer of magnetic helicity via reconnection.
- Ejection Velocities: Individual spicules reached ejection velocities of approximately 90 km s $^{-1}$ . The authors suggest that the concentration of magnetic energy from extremely small-scale eruptions into a single structure may facilitate more efficient conversion to kinetic energy.
Magnetic Environment: In the few cases where magnetic data was resolvable (3 out of 30 events due to the small scale and weak fields), microfilaments were located along polarity inversion lines (PILs), suggesting magnetic flux cancellation as a trigger mechanism. No distinct EUV brightening was detected in AIA 171 Å images, likely due to the small spatial scale of the events relative to the AIA resolution, though integrated intensity peaks coincided with eruption times.

Significance and Claims
The paper claims to provide compelling observational evidence that spicules can be triggered by microfilament eruptions, filling a gap in the hierarchy of solar eruptive phenomena. The study supports the hypothesis that solar eruptive events across vastly different spatial scales—from coronal jets down to spicules—share a unified physical mechanism driven by magnetic reconnection.

Key conclusions include:

Scale-Dependent Morphology: The physical scale of the driving microfilament governs the resulting spicular morphology, ranging from individual jets (small scales) to enhanced clusters (larger scales).
Global Implications: By extrapolating the observed event rate ( $\sim 0.014$ events hr $^{-1}$ Mm $^{-2}$ ) to the global solar surface, the authors estimate $\sim 8.5 \times 10^4$ microfilament eruptions per hour globally. While this number is lower than the total estimated number of spicules, the authors note that a single microfilament often drives a cluster of spicules, suggesting that microfilament eruptions could account for at least a significant fraction of the global spicule population.
Resolution Breakthrough: The results demonstrate that the unprecedented spatial resolution of DKIST is essential for resolving the fine-scale magnetic structures and dynamics previously inaccessible to ground-based and space-based telescopes, thereby validating the microfilament eruption model for spicule formation.