Gamma-ray bursts (GRBs) are the shortest but most energetic explosions in the universe. The mechanism behind their prompt emission remains unclear: the internal shock model, where energy is extracted from the kinetic energy of colliding shells, competes with the Poynting-flux-dominated model, where energy is stored in the magnetic field and released via reconnection. Statistical studies that pooled pulses from different bursts found similarities with solar flares and hinted at self-organized criticality (SOC)—a state where a system maintains itself at a critical point and produces avalanches of all sizes. However, due to the small number of pulses in a single burst and systematic errors when combining samples, the question remained open. This work joins the search for common statistical patterns in gamma-ray bursts, solar flares, and X-ray flares, but for the first time uses a single exceptionally bright burst with hundreds of pulses.
Data from the GECAM satellite (Gravitational wave high-energy electromagnetic counterpart all-sky monitor) were used for GRB 230307A, the second brightest burst ever observed. Thanks to a special anti-saturation design of the detectors, an accurate light curve was obtained without losses even at extreme flux. In eight energy channels (from 30 to 6000 keV), the MEPSA algorithm (peak search) identified pulses with a signal-to-noise ratio above 5. For each pulse, the peak time, peak count (a measure of intensity), duration, and waiting time between adjacent pulses were measured. Cumulative distributions of these quantities were then constructed and fitted with broken power laws. Additionally, Fourier power spectra were calculated and Monte Carlo simulations were performed to test hypotheses.
In each energy channel, between 51 and 98 pulses were found. The cumulative distributions of peak counts, durations, and waiting times exhibit power-law tails, indicating the absence of a characteristic scale—a hallmark of self-organized criticality. The power-law indices depend on energy: they are steeper in low-energy channels but plateau at energies above ~150 keV. For high energies, the slopes of the duration and waiting time distributions are about 2.0, and the peak count slope is about 1.7. These values match theoretical predictions for three-dimensional SOC with classical diffusion (β=1, S=3): $α_T$ = α_Δt = 2, $α_P$ = 1.67. A correlation between duration and peak count, T ∝ $P^{-1/2}$, was also found, corresponding to the expected energy-time dependence E ∝ $T^{-1}$ for magnetic reconnection. The Fourier power spectra have slopes of 1.85–2.37, consistent with simulations of the ICMART model (internal collisions triggering magnetic reconnection and turbulence).
This work is the first to show that self-organized criticality appears in the prompt emission of a single gamma-ray burst, not just in combined samples. This eliminates concerns about selection effects and systematic errors. The obtained power-law slopes correspond to three-dimensional SOC, consistent with the ICMART model, where shell collisions distort the magnetic field to a critical state, triggering a cascade of reconnections. Unlike neighboring studies that pooled pulses from many bursts, here a single object with hundreds of pulses was used, making the conclusions more robust. The similarity with solar flares strengthens the argument for a common mechanism—magnetic reconnection in a relativistic jet.
Future observations of bright gamma-ray bursts with high time resolution detectors will allow systematic searches for SOC behavior and refine power-law parameters. This will provide constraints on the magnetic field structure and dissipation physics in relativistic jets. It may also be possible to link observed slopes to details of turbulence and reconnection, and to test predictions for different central engine models (black hole or magnetar).
The results are important for gamma-ray burst physics, high-energy astrophysics, and plasma physics, as they connect macroscopic statistics to microscopic reconnection processes.
Conduct a similar analysis for other bright bursts with good time resolution, such as GRB 221009A. Compare power-law slopes with predictions from numerical models of magnetic reconnection in relativistic plasma.
This work directly addresses the unresolved problem of the energy release mechanism in gamma-ray bursts: whether kinetic or magnetic energy dominates the jet. The detection of SOC supports the magnetic model but does not completely rule out internal shocks. The nature of the central engine and the spatial distribution of turbulence and reconnection remain open questions.
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What the work does
The study analyzes gamma-ray burst GRB 230307A using GECAM data. Hundreds of pulses were identified across eight energy bands, and their peak counts, durations, and waiting times were measured. The distributions of these quantities follow power laws with slopes consistent with predictions of three-dimensional self-organized criticality, and a correlation between duration and peak count was found.
Where its strength is
The strength of the work lies in using a single exceptionally bright event with high temporal resolution and a large number of pulses, allowing for the first time to test SOC statistics in an individual gamma-ray burst without systematic errors from sample stacking.
Where it could go next
Worth trying
Why this may matter
Confirming self-organized criticality in an individual gamma-ray burst strengthens magnetically dominated models and may help understand particle acceleration and radiation mechanisms in extreme astrophysical conditions.
Nearby works in our archive
The closest work in the archive sits at 0.64 by meaning — the usual level for our corpus.
GRB 230307A was so bright that ordinary gamma-ray detectors would have saturated, but GECAM had special anti-saturation protection and recorded everything without loss. The burst lasted about 35 seconds, yet released energy comparable to what the Sun emits over billions of years.