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arxiv: 2604.22145 · v1 · submitted 2026-04-24 · 🌌 astro-ph.SR

Repeated Sunspot Light Bridge Jets Associated with Slipping Base Brightenings

Yadan Duan , Xiaoli Yan , Yuhang Gao , Jincheng Wang , Zhe Xu , Yongyuan Xiang This is my paper

Pith reviewed 2026-05-08 10:12 UTC · model grok-4.3

classification 🌌 astro-ph.SR
keywords light bridge jetssunspotmagnetic reconnectionslipping reconnectionsolar jetsconvective upflowsphotospheric motionumbral field
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The pith

Repeated 3D reconnection between horizontal light-bridge fields and vertical umbral fields drives recurrent jets in sunspots.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper examines six recurrent jets along a sunspot light bridge with high-resolution data from ground-based telescopes. Each jet begins with a base point that slips horizontally at 0.6-1.5 km/s, timed with quasi-periodic photospheric horizontal motions of 1.3-6.5 km/s driven by convection. Spectral signatures at the base points match Ellerman bombs, confirming reconnection. The authors conclude that repeated three-dimensional reconnection at the interface between the bridge's horizontal field and the surrounding vertical umbral field powers the jets, with the process modulated by convective upflows and magnetic flux transport along the bridge. This links the jets to the same reconnection physics seen in larger coronal jets.

Core claim

Recurrent light bridge jets arise from repeated 3D reconnection between the horizontal magnetic field inside the light bridge and the ambient vertical umbral field. The reconnection is driven and modulated by quasi-periodic horizontal motion fueled by convective upflows and the transport of magnetic flux along the light bridge, as shown by the slipping jet base points, their temporal correlation with photospheric flows, and Ellerman-bomb-like spectral features at the reconnection sites.

What carries the argument

Slipping 3D reconnection at the boundary between the light bridge's horizontal field and the vertical umbral field, modulated by convective horizontal motions and flux transport.

If this is right

  • Some light bridge jets operate through the same reconnection process as coronal jets.
  • Quasi-periodic convective motions along light bridges can repeatedly trigger small-scale eruptive events.
  • Slipping reconnection can be observed directly along sunspot light bridges.
  • Magnetic flux transport along the bridge controls the recurrence and modulation of the jets.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same reconnection geometry may operate wherever horizontal and vertical fields meet in the solar atmosphere.
  • Numerical experiments that include convective upflows could test how the observed quasi-periodicity sets the jet recurrence interval.
  • Even higher-resolution magnetograms might isolate the exact sites of flux emergence or cancellation that sustain the horizontal motions.

Load-bearing premise

The observed timing match between slipping jet base points, photospheric horizontal motions, and jet spires is enough to show that convective upflows and flux transport causally drive or modulate the repeated reconnection.

What would settle it

A sample of similar light bridge jets in which the base-point slipping and photospheric flows lack temporal correlation would break the proposed causal link.

Figures

Figures reproduced from arXiv: 2604.22145 by Jincheng Wang, Xiaoli Yan, Yadan Duan, Yongyuan Xiang, Yuhang Gao, Zhe Xu.

Figure 1
Figure 1. Figure 1: Overview of the sunspot, light bridge, and LB jets in AR 14153 on 2025 July 30. (A) The longitudinal magnetic field at 02:00 UT shows the magnetic environment of the source region. (B) NVST TiO image at 02:45 UT, and the field of view (FOV) is indicated by the white box in (A). The cyan arrow denotes the horizontal motion along the light bridge. (C1)−(C6) NVST Hα -0.6˚A images show six of the LB jets eject… view at source ↗
Figure 2
Figure 2. Figure 2: (A)−(F) Zoomed-in snapshots showing the evolution of an LB jet from 02:41 UT to 02:50 UT in NVST TiO, Hα -0.6 ˚A , AIA 1600 ˚A , 171˚A images and Doppler proxy maps. The black arrows and the cyan circles in panels (A) and (B) denote a horizontal motion front along the light bridge. The white and black arrows in panel (C)−(E) point out the bright footpoints at the base of the LB jet. The red circle marks th… view at source ↗
Figure 3
Figure 3. Figure 3: Similar to view at source ↗
Figure 4
Figure 4. Figure 4: The dashed curves in the CHASE Dopper map, NVST, and CHASE images show the light bridge of our interest. The green Hα profiles of selected points in panels (g)−(i) are marked with green diamond symbols in (d)−(f). And the dashed lines represent the reference Hα profile. Liu, Z., Xu, J., Gu, B.-Z., et al. 2014, Research in Astronomy and Astrophysics, 14, 705, doi: 10.1088/1674-4527/14/6/009 Louis, R. E., Be… view at source ↗
Figure 5
Figure 5. Figure 5: Time-distance map along slices C1−C4 and S1−S4 shown in Figures 2 and 3. Panels (A1) and (B1) show the horizontal motion in the LB at different times. Panels (A2), (B2), (A3), and (B3) show the slipping bright footpoints in the LB for the different images of NVST Hα off-band and AIA 1600 ˚A . The red arrows in panels (A2) and (A3) mark the merged position between a bright patch and a slipping bright footpo… view at source ↗
Figure 6
Figure 6. Figure 6: (a) NVST TiO image at 03:26 UT. (b) The SDO/HMI vector magnetogram at 03:48 UT. Green arrows represent the strength and direction of the transverse magnetic fields. The boundaries between the sunspot and the LB are highlighted by red circles. (c) NVST Hα off-band at 03:01 UT. (d) The field of view in panel (d) corresponds to the cyan box indicated in panel (c), showing the photospheric flow fields derived … view at source ↗
read the original abstract

Light bridge (LB) jets offer a unique window into small-scale eruptive phenomena within sunspots, the Sun's strongest magnetic environments; however, their generation mechanism remains a subject of debate. Using high-resolution observations from the New Vacuum Solar Telescope (NVST), we investigated six recurrent light bridge jets and the slipping motions of their jet base points (JBPs). Analogous to coronal jets, our observations show that these LB jets are characterized by a preceding JBP followed by a collimated jet spire. The JBP of each repeated jet along the LB displays apparent slipping motion at velocities of 0.6-1.5 km/s, which is temporally correlated with quasi-periodic enhanced photospheric horizontal motion of 1.3-6.5 km/s. Following the slipping JBPs, the resulting jet spires' fronts display similar slipping behaviors within the upper solar atmosphere. The Chinese Ha Solar Explorer (CHASE) reveals Ellerman-bomb-like spectral signatures at the JBPs, confirming that magnetic reconnection is operating at the jet base. Based on these results, we propose that repeated 3D reconnection occurring between the horizontal LB field and the ambient vertical umbral field may drive these LB jets. This process appears to be driven and/or modulated by quasi-periodic horizontal motion fueled by convective upflows and the transport of magnetic flux along the light bridge. This work suggests that some LB jets share a common reconnection-driven mechanism with coronal jets and provides direct evidence of slipping reconnection occurring along the sunspot light bridge.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

3 major / 2 minor

Summary. The paper reports high-resolution NVST and CHASE observations of six recurrent light-bridge jets in a sunspot. Each jet is preceded by a jet base point (JBP) that exhibits apparent slipping motion (0.6–1.5 km s⁻¹) temporally correlated with quasi-periodic photospheric horizontal motions (1.3–6.5 km s⁻¹). The JBPs show Ellerman-bomb-like Hα spectra, and the jet spires display analogous slipping. The authors interpret these features as evidence for repeated 3D reconnection between the horizontal light-bridge field and the ambient vertical umbral field, with the reconnection driven or modulated by convective upflows and magnetic-flux transport along the bridge.

Significance. If the causal interpretation is substantiated, the work supplies direct observational evidence that slipping reconnection operates along sunspot light bridges and that some LB jets share the same reconnection-driven mechanism as coronal jets. The combination of high-resolution imaging, spectral confirmation, and multi-height slipping signatures strengthens the case for 3D reconnection in strong-field environments and offers a concrete observational template for future modeling.

major comments (3)
  1. [Abstract and §4] Abstract and §4 (Discussion): the central claim that 'quasi-periodic horizontal motion fueled by convective upflows and the transport of magnetic flux' drives or modulates the reconnection rests on temporal correlations and morphological analogies. No vertical-velocity maps, flux-transport-rate calculations, or energy-budget comparisons are presented to convert the observed 1.3–6.5 km s⁻¹ motions into a demonstrated causal driver or to exclude alternatives such as p-mode leakage or independent flux emergence.
  2. [§3] §3 (Observations and Analysis): the manuscript reports apparent slipping velocities but provides neither error estimates on the measured speeds nor a quantitative assessment of projection effects or line-of-sight confusion. Without these, the claimed 3D reconnection geometry and the analogy to coronal-jet slipping remain interpretive rather than demonstrated.
  3. [§4] §4: the proposal of repeated 3D reconnection between horizontal LB and vertical umbral fields is plausible but would be strengthened by at least a schematic magnetic topology or reference to existing MHD simulations that reproduce the observed slipping speeds and recurrence; none is supplied.
minor comments (2)
  1. [Figures and §3] Figure captions and text occasionally use 'apparent slipping' and 'slipping' interchangeably; a brief clarification of the distinction between observed plane-of-sky motion and inferred 3D reconnection would improve readability.
  2. [§3.2] The CHASE spectral analysis is summarized but the exact line-profile fitting parameters or reference spectra used to classify the JBPs as Ellerman-bomb-like are not tabulated; adding these would allow independent verification.

Simulated Author's Rebuttal

3 responses · 1 unresolved

We thank the referee for the constructive and detailed report. The comments highlight important areas where the manuscript can be strengthened with additional quantitative details and clarifications. We address each major comment below and will revise the manuscript accordingly where feasible.

read point-by-point responses

  1. Referee: [Abstract and §4] the central claim that 'quasi-periodic horizontal motion fueled by convective upflows and the transport of magnetic flux' drives or modulates the reconnection rests on temporal correlations and morphological analogies. No vertical-velocity maps, flux-transport-rate calculations, or energy-budget comparisons are presented to convert the observed 1.3–6.5 km s⁻¹ motions into a demonstrated causal driver or to exclude alternatives such as p-mode leakage or independent flux emergence.

    Authors: We agree that the causal interpretation is primarily supported by temporal correlations and morphological evidence rather than direct measurements of vertical flows or quantitative energy budgets. The current NVST and CHASE datasets provide high-resolution Hα imaging and spectra but do not include the necessary Doppler maps for reliable vertical velocity measurements at the required cadence and resolution. In the revision we will expand the discussion to explicitly address why p-mode leakage is less favored (localized reconnection signatures and Ellerman-bomb-like spectra) and will include approximate flux-transport estimates based on the observed horizontal speeds and assumed field strengths, while clearly stating the limitations. We will also reference supporting literature on convective modulation of reconnection. revision: partial

  2. Referee: [§3] the manuscript reports apparent slipping velocities but provides neither error estimates on the measured speeds nor a quantitative assessment of projection effects or line-of-sight confusion. Without these, the claimed 3D reconnection geometry and the analogy to coronal-jet slipping remain interpretive rather than demonstrated.

    Authors: We accept this point. In the revised §3 we will add formal error estimates on the slipping velocities (0.6–1.5 km s⁻¹) derived from spatial resolution, time sampling, and manual tracking uncertainties. We will also include a quantitative discussion of projection effects given the near-disk-center location of the target and the geometry of the light bridge, arguing that the observed bidirectional slipping is unlikely to be dominated by line-of-sight confusion. These additions will make the 3D reconnection interpretation more robust. revision: yes

  3. Referee: [§4] the proposal of repeated 3D reconnection between horizontal LB and vertical umbral fields is plausible but would be strengthened by at least a schematic magnetic topology or reference to existing MHD simulations that reproduce the observed slipping speeds and recurrence; none is supplied.

    Authors: We will incorporate both suggestions. A new schematic figure will be added to §4 illustrating the proposed 3D reconnection geometry between the horizontal light-bridge field and the ambient vertical umbral field, including the expected slipping motion of the reconnection site. We will also cite relevant MHD simulations of slipping reconnection (e.g., those modeling coronal jets and light-bridge dynamics) that produce comparable speeds and quasi-periodic behavior, thereby placing our observations in a firmer theoretical context. revision: yes

standing simulated objections not resolved
  • Direct vertical-velocity maps and full energy-budget calculations cannot be provided from the existing NVST/CHASE dataset without new observations or complementary instruments.

Circularity Check

0 steps flagged

No circularity; observational correlations interpreted via standard reconnection physics

full rationale

The manuscript reports high-resolution NVST and CHASE observations of recurrent LB jets, measures apparent slipping velocities of JBPs (0.6-1.5 km/s) and photospheric motions (1.3-6.5 km/s), notes their temporal correlation, and identifies Ellerman-bomb-like spectra at the bases. It then proposes that repeated 3D reconnection between horizontal LB and vertical umbral fields is driven or modulated by convective upflows and flux transport. No equations, parameter fits, or self-citations appear in the derivation chain; the proposal is an interpretive synthesis of direct observables rather than a reduction of any predicted quantity to prior fitted inputs or self-referential theorems. The central claim therefore remains self-contained against external solar-physics benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The paper rests on standard solar magnetic field geometry and reconnection physics; no free parameters or new invented entities are introduced.

axioms (2)
  • domain assumption Magnetic reconnection releases energy and produces observable brightenings and jets in the solar atmosphere
    Invoked to interpret Ellerman-bomb signatures and jet formation at the JBPs.
  • domain assumption Apparent slipping motions of bright points trace the progress of 3D reconnection along magnetic field lines
    Used to link observed JBP slipping to the proposed reconnection geometry.

pith-pipeline@v0.9.0 · 5591 in / 1523 out tokens · 73350 ms · 2026-05-08T10:12:47.810418+00:00 · methodology

discussion (0)

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Reference graph

Works this paper leans on

3 extracted references · 2 canonical work pages

  1. [1]

    T., & Kurokawa, H

    Asai, A., Ishii, T. T., & Kurokawa, H. 2001, ApJL, 555, L65, doi: 10.1086/321738 Aulanier, G., Pariat, E., D´ emoulin, P., & Devore, C. R. 2006, SoPh, 238, 347, doi: 10.1007/s11207-006-0230-2 8 Figure 2.(A)−(F) Zoomed-in snapshots showing the evolution of an LB jet from 02:41 UT to 02:50 UT in NVST TiO, Hα-0.6 ˚A , AIA 1600 ˚A , 171˚A images and Doppler p...

    work page doi:10.1086/321738 2001

  2. [2]

    Panels (A2), (B2), (A3), and (B3) show the slipping bright footpoints in the LB for the different images of NVST Hαoff-band and AIA 1600 ˚A

    Panels (A1) and (B1) show the horizontal motion in the LB at different times. Panels (A2), (B2), (A3), and (B3) show the slipping bright footpoints in the LB for the different images of NVST Hαoff-band and AIA 1600 ˚A . The red arrows in panels (A2) and (A3) mark the merged position between a bright patch and a slipping bright footpoint. Panels (A4) and (...

    2025

  3. [3]

    b The speeds of horizontal motion derived from a fitting linear function in NVST TiO image as displayed in Figure 6 (e)

    a The Time represents the time period during which the LB jets occur in the Hαblue wing of NVST. b The speeds of horizontal motion derived from a fitting linear function in NVST TiO image as displayed in Figure 6 (e). c The slipping speeds of bright points come from a fitting linear function in NVST Hα-0.6 ˚A . d The slipping speeds of the plasma at the l...

    work page doi:10.1126/science.aaw2796 1995