🔭 astrophysics

Repeated Sunspot Light Bridge Jets Associated with Slipping Base Brightenings

Using high-resolution observations from the NVST and CHASE, this study demonstrates that repeated light bridge jets in sunspots are driven by 3D magnetic reconnection between horizontal light bridge fields and vertical umbral fields, a process evidenced by slipping motions of the jet base points and Ellerman-bomb-like spectral signatures.

Original authors: Yadan Duan, Xiaoli Yan, Yuhang Gao, Jincheng Wang, Zhe Xu, Yongyuan Xiang

Published 2026-04-27

📖 3 min read☕ Coffee break read

CC BY 4.0

Original authors: Yadan Duan, Xiaoli Yan, Yuhang Gao, Jincheng Wang, Zhe Xu, Yongyuan Xiang

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

The Sun’s "Light Bridge" Fireworks: A Story of Magnetic Tug-of-War

Imagine a massive, dark, swirling storm on the surface of the Sun—a sunspot. These sunspots are like giant magnetic anchors, holding down the Sun’s atmosphere with incredible force. Sometimes, a bright strip of light cuts through the middle of this dark storm. Scientists call this a "Light Bridge."

Think of the sunspot as a dark, heavy velvet curtain, and the Light Bridge as a bright, glowing crack running through the middle of it. This paper describes how that "crack" occasionally shoots off mini-fireworks called Light Bridge Jets.

Here is the breakdown of what the researchers discovered, using a few simple analogies.

1. The Setup: The Magnetic Tug-of-War

Inside the sunspot, the magnetic fields are standing straight up and down, like a forest of stiff, vertical trees. But inside the Light Bridge, the magnetic fields are lying flat, like fallen logs.

Where these two meet—the vertical "trees" and the horizontal "logs"—there is a massive amount of tension. It’s like a high-stakes tug-of-war happening at the boundary. The "logs" are constantly being pushed and shoved by the boiling, churning plasma of the Sun.

2. The Trigger: The "Slipping" Dance

The researchers noticed something fascinating: these jets don't just pop up randomly. They follow a specific pattern.

Imagine you are holding a heavy rope (the magnetic field) and someone else is pulling it from the other side. If you start sliding your hands along the rope while pulling, the tension changes and moves. This is what the scientists call "Slipping Reconnection."

They observed "bright spots" at the base of the jets that weren't staying still. Instead, they were sliding or "slipping" along the edge of the Light Bridge. This sliding motion is the "spark" that triggers the explosion. As the magnetic lines "slip" past each other, they snap and reconnect, releasing a burst of energy.

3. The Explosion: The Peacock’s Tail

When that magnetic snap happens, it launches a jet of hot gas upward into the Sun's atmosphere.

The researchers described the jets as looking like a peacock spreading its tail. Because the jets happened repeatedly, they created a beautiful, fanning pattern of light. Each time the "tug-of-war" reached a breaking point, a new jet was shot out, following the path of the sliding magnetic lines.

4. The "Engine": Convection Upflows

What keeps this cycle going? The researchers believe the "engine" is the Sun's internal boiling motion (convection).

Think of it like a conveyor belt under the Light Bridge. This conveyor belt constantly carries new magnetic "logs" toward the edge of the sunspot. Every time a new batch of magnetic material arrives, it hits the vertical "trees," triggers a "slip," and shoots off a new jet. This is why the jets are recurrent—they keep coming back as long as the conveyor belt keeps running.

Summary in a Nutshell

The Location: A bright crack (Light Bridge) inside a dark magnetic storm (Sunspot).
The Action: Magnetic fields are "slipping" and sliding past each other like two people trying to pass in a narrow hallway.
The Result: Every time they slip, they snap, launching a "firework" (Jet) into space.
The Big Discovery: This proves that these small sunspot jets work almost exactly like the massive, violent solar jets seen elsewhere, just on a smaller, more localized scale.

Technical Summary: Repeated Sunspot Light Bridge Jets Associated with Slipping Base Brightenings

1. Problem Statement

Sunspot light bridges (LBs) are regions of relatively weak, horizontal magnetic fields embedded within the strong, vertical magnetic environment of a sunspot umbra. While light bridge (LB) jets—plasma ejections from these regions—are known to occur, their precise generation and driving mechanisms remain a subject of debate. Specifically, the three-dimensional (3D) nature of the reconnection process and how photospheric dynamics (such as convection and flux transport) modulate these chromospheric eruptions have not been clearly established through direct observation.

2. Methodology

The study employs a multi-wavelength, high-resolution observational approach to capture the spatiotemporal evolution of solar plasma across different atmospheric layers. The researchers analyzed a specific event on July 30, 2025, in active region NOAA 14153. Key instruments and data used include:

NVST (New Vacuum Solar Telescope): Provided high-resolution $H\alpha$ imaging (chromosphere) and TiO imaging (photosphere) to track jet morphology and horizontal photospheric motions.
CHASE (Chinese H $\alpha$ Solar Explorer): Provided $H\alpha$ imaging spectroscopy to identify spectral signatures (e.g., Ellerman-bomb-like profiles) at the jet bases.
SDO/AIA (Solar Dynamics Observatory/Atmospheric Imaging Assembly): Captured the response of the plasma in the transition region (171 Å) and lower corona (1600 Å).
SDO/HMI (Helioseismic and Magnetic Imager): Provided vector magnetograms to analyze the magnetic shear and field configuration at the LB boundary.
Analytical Techniques: Used Doppler proxy maps to identify plasma flows (redshifts/blueshifts), time-distance diagrams to track kinematic evolution, and optical flow algorithms to quantify photospheric horizontal velocities.

3. Key Results

Identification of Repeated Jets: The team observed six recurrent LB jets. Each event followed a consistent sequence: a preceding Jet Base Brightening (JBP) followed by a collimated jet spire.
Slipping Motion Discovery: The JBPs exhibited "slipping" motions at velocities of 0.6–1.5 km s⁻¹. This slipping behavior was mirrored by the leading edges of the jet spires in the upper atmosphere.
Photospheric-Chromospheric Coupling: A critical finding was the tight temporal and spatial correlation between the slipping JBPs and quasi-periodic horizontal motions in the photosphere (1.3–6.5 km s⁻¹). The photospheric motions appear to drive or modulate the reconnection sites.
Spectroscopic Evidence: CHASE observations revealed $H\alpha$ profiles characterized by intense wing enhancement (similar to Ellerman bombs), providing direct evidence of magnetic reconnection occurring in the lower atmosphere/upper photosphere.
Magnetic Configuration: Magnetograms confirmed high magnetic shear at the boundary between the horizontal LB fields and the vertical umbral fields, identifying this boundary as the ideal site for 3D reconnection.

4. Key Contributions

Evidence of 3D Slipping Reconnection: The paper provides rare, direct observational evidence of 3D slipping magnetic reconnection occurring specifically in the lower solar atmosphere above a light bridge.
Unified Mechanism: It demonstrates that LB jets share a common physical driver—magnetic reconnection—with other solar phenomena like coronal jets and macrospicules.
Driving Model: The study proposes a model where convective upflows in the LB transport magnetic flux horizontally. This transport pushes the field lines against the ambient umbral field, triggering periodic 3D reconnection events.

5. Significance

This work advances our understanding of small-scale solar eruptions by bridging the gap between photospheric magnetoconvection and chromospheric/coronal dynamics. By proving that photospheric horizontal motions can trigger and modulate 3D slipping reconnection, the study provides a mechanistic link between surface plasma flows and the energy release processes that heat the solar atmosphere. It establishes LB jets as a vital laboratory for studying the complexities of magnetic reconnection in high-field environments.