Particle Acceleration Time due to Turbulent-Induced Magnetic Reconnection
Pith reviewed 2026-05-23 18:46 UTC · model grok-4.3
The pith
Acceleration time stays nearly independent of particle energy in the Fermi regime of turbulent reconnection.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The acceleration time during the Fermi regime remains nearly independent of particle energy and aligns with the acceleration time theoretical relations up to the threshold energy, attained when the particles Larmor radius becomes as large as the thickness of the largest current sheets. Beyond this threshold, the acceleration regime shifts to the slower drift regime, showing strong energy dependence. The results also indicate a clear dominance of the Fermi regime of acceleration.
What carries the argument
Average acceleration time computed from statistical distributions of current-sheet thicknesses and reconnection velocities, validated against direct tracking of 50,000 particles in the jet simulation.
If this is right
- Fermi-regime acceleration operates with constant time until the Larmor-radius threshold, allowing rapid energy gain across many decades.
- After the threshold the process switches to drift acceleration whose time scales with energy, slowing further gains.
- The Fermi regime dominates the overall acceleration process in the turbulent jet.
- The three conditions for reconnection acceleration time identified by Xu and Lazarian are satisfied by the measured distributions.
Where Pith is reading between the lines
- The same threshold behavior may set an upper limit on the energies that can be reached efficiently in other turbulent reconnection sites such as the solar corona.
- If the largest current sheets are thinner in real jets than in the simulation, the Fermi regime would extend to higher energies.
- The energy-independent phase could allow particles to reach the knee of the cosmic-ray spectrum before drift effects become important.
Load-bearing premise
The statistical distributions of current-sheet thicknesses and reconnection velocities can be averaged over time to produce a representative acceleration time that matches the time measured by tracking individual particles.
What would settle it
A direct measurement showing that acceleration time in the Fermi regime varies strongly with particle energy even while the Larmor radius remains smaller than the largest current-sheet thickness.
Figures
read the original abstract
We numerically investigate a crucial parameter for understanding particle acceleration theory via turbulence-induced magnetic reconnection: the particle acceleration time. We examine particles accelerated either during the jet's dynamic evolution or in a post-processing, nearly stationary regime. We derive the particle acceleration time and compare it with theoretical predictions for both the Fermi and drift regimes identified in the simulations. In the Fermi regime, the acceleration time is expected to be independent of the particles' energy, for constant reconnection velocity, as energy increases exponentially with time. Conversely, we expect the reconnection acceleration time to depend on the current sheet's thickness and the reconnection velocity, a dependence recently revisited by xu and lazarian 2023. They identified three conditions for \(t_{acc}\). We tested these relations using statistical distributions of the current sheets' thickness and reconnection velocities in the turbulent jet over time. The resulting average value of \(t_{acc}\) was found to be nearly constant with particle energy. We compared this acceleration time with the average acceleration time derived directly from 50,000 particles accelerated in situ in the same relativistic jet. When considering a longer time interval for particle acceleration in a nearly stationary snapshot of the turbulent jet, we find that the acceleration time during the Fermi regime remains nearly independent of particle energy and aligns with the acceleration time theoretical relations up to the threshold energy, attained when the particles Larmor radius becomes as large as the thickness of the largest current sheets. Beyond this threshold, the acceleration regime shifts to the slower drift regime, showing strong energy dependence, as predicted. The results also indicate a clear dominance of the Fermi regime of acceleration.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript numerically investigates the particle acceleration time t_acc in turbulence-induced magnetic reconnection within a relativistic jet simulation. The authors compute an average t_acc from statistical distributions of current sheet thicknesses and reconnection velocities over time, test it against the three conditions in Xu & Lazarian (2023), and compare the result to the average t_acc obtained from direct tracking of 50,000 particles. They report that t_acc remains nearly energy-independent in the Fermi regime (consistent with exponential energy growth at constant reconnection velocity) up to a threshold where the Larmor radius equals the thickness of the largest current sheets, after which acceleration shifts to the slower, energy-dependent drift regime, with clear dominance of the Fermi process. Comparisons are performed both during the jet's dynamic evolution and in a post-processing nearly stationary regime.
Significance. If the central comparison holds, the work supplies numerical support for the Xu & Lazarian (2023) acceleration-time relations in a turbulent reconnection setting and identifies a concrete energy threshold for the Fermi-to-drift transition. This would be useful for modeling nonthermal particle spectra in astrophysical jets. The direct tracking of 50,000 particles provides a statistically meaningful benchmark against the distribution-derived average.
major comments (2)
- [Abstract / Results] Abstract (and the results section describing the averaging procedure): The claim that the global statistical average of t_acc from current-sheet distributions is representative and matches the average from direct particle tracking rests on the untested assumption that these distributions faithfully sample the reconnection events actually encountered by the tracked particles. Trajectory selection, residence-time weighting, and the post-processing stationary snapshot could bias the subset of events experienced by particles; without showing the distribution of per-particle t_acc values or demonstrating that the averaging accounts for encounter probabilities, the reported near-independence of t_acc and the dominance of the Fermi regime could be an artifact of the procedure rather than a validation of the physics.
- [Abstract] Abstract: The threshold energy is identified when the particle Larmor radius equals the thickness of the largest current sheets, yet the manuscript provides no quantitative detail on how the largest-sheet thickness is extracted from the time-dependent distributions or which magnetic-field value is used to compute r_L in the simulation. This definition is load-bearing for locating the Fermi-to-drift transition and for the claim that the alignment with theory holds only up to that point.
minor comments (2)
- [Abstract] Abstract contains inconsistent capitalization and citation style: 'xu and lazarian 2023' should read 'Xu & Lazarian (2023)'; 'Larmor' should be consistently capitalized.
- [Abstract] The abstract refers to 'a longer time interval for particle acceleration in a nearly stationary snapshot' without specifying the interval length, the criterion used to assess stationarity, or how the snapshot is selected from the turbulent jet evolution.
Simulated Author's Rebuttal
We thank the referee for the thorough review and insightful comments. We address each major comment point by point below and indicate where revisions will be made.
read point-by-point responses
-
Referee: [Abstract / Results] Abstract (and the results section describing the averaging procedure): The claim that the global statistical average of t_acc from current-sheet distributions is representative and matches the average from direct particle tracking rests on the untested assumption that these distributions faithfully sample the reconnection events actually encountered by the tracked particles. Trajectory selection, residence-time weighting, and the post-processing stationary snapshot could bias the subset of events experienced by particles; without showing the distribution of per-particle t_acc values or demonstrating that the averaging accounts for encounter probabilities, the reported near-independence of t_acc and the dominance of the Fermi regime could be an artifact of the procedure rather than a validation of the physics.
Authors: We acknowledge that the comparison of averages assumes the distributions capture the events experienced by tracked particles. The manuscript shows that the two independent averages agree closely in the Fermi regime, which provides supporting evidence that the procedure is representative. To strengthen this and directly address possible biases from trajectory selection or weighting, the revised manuscript will include the distribution of per-particle t_acc values together with a brief discussion of how the averaging incorporates encounter probabilities. These additions will appear in the results section. revision: yes
-
Referee: [Abstract] Abstract: The threshold energy is identified when the particle Larmor radius equals the thickness of the largest current sheets, yet the manuscript provides no quantitative detail on how the largest-sheet thickness is extracted from the time-dependent distributions or which magnetic-field value is used to compute r_L in the simulation. This definition is load-bearing for locating the Fermi-to-drift transition and for the claim that the alignment with theory holds only up to that point.
Authors: We agree that quantitative details on the extraction of the largest current-sheet thickness and the precise B value for r_L are needed. The revised manuscript will specify the criterion used to identify the maximum thickness from the time-dependent distributions (e.g., the highest value recorded across snapshots) and will state the magnetic-field value employed for the Larmor-radius calculation. These clarifications will be added to the abstract and results sections. revision: yes
Circularity Check
No circularity; derivation relies on independent simulation statistics and external theory
full rationale
The paper computes an average t_acc from the statistical distributions of current-sheet thickness and reconnection velocity drawn from the turbulent jet simulation, then compares that average both to the external Xu & Lazarian (2023) relations and to a separate direct-tracking average obtained from 50,000 particles. No equation or claim reduces the reported constancy or the Fermi-regime dominance to a fitted parameter, a self-citation, or a definitional identity; the two averaging procedures are presented as distinct checks whose agreement is offered as evidence rather than presupposed. The cited theoretical relations originate outside the author set and are not invoked as a uniqueness theorem that forces the present result.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Turbulent magnetic reconnection occurs in relativistic jets and leads to particle acceleration in Fermi and drift regimes.
- domain assumption The reconnection velocity is constant in the Fermi regime, making acceleration time independent of energy.
Reference graph
Works this paper leans on
-
[1]
, " * write output.state after.block = add.period write newline
ENTRY address archivePrefix author booktitle chapter doi edition editor eprint howpublished institution journal key month note number organization pages publisher school series title misctitle type volume year version url label extra.label sort.label short.list INTEGERS output.state before.all mid.sentence after.sentence after.block FUNCTION init.state.co...
-
[2]
" write newline "" before.all 'output.state := FUNCTION format.doi doi empty "" "doi:" doi * if FUNCTION format.url url empty "" new.block "" url * "" * if FUNCTION format.eprint eprint empty "" archivePrefix empty "" archivePrefix ":" * if eprint field.or.null * if FUNCTION format.pid eprint empty format.doi format.eprint if FUNCTION n.dashify 't := "" t...
-
[3]
- [1] #1 = = ^ ^ ^ .\!\!^ d .\!\!^ h .\!\!^ m .\!\!^ s .\!\!^ @mss
thebibliography [1] 20pt to REFERENCES 6pt =0pt 10pt plus 3pt =0pt =0pt =1pt plus 1pt =0pt =0pt -12pt =13pt plus 1pt =20pt =13pt plus 1pt \@M =10000 =-1.0em =0pt =0pt 0pt =0pt =1.0em @enumiv\@empty 10000 10000 `\.\@m \@noitemerr \@latex@warning Empty `thebibliography' environment \@ifnextchar \@reference \@latexerr Missing key on reference command Each re...
-
[4]
Alves , E. P., Zrake , J., & Fiuza , F. 2018, , 121, 245101
work page 2018
-
[5]
2013, in Particle Acceleration in Cosmic Plasmas
Arons , J. 2013, in Particle Acceleration in Cosmic Plasmas. Series: Space Sciences Series of ISSI, ed. A. Balogh , A. Bykov , R. P. Lin , J. Raymond , & M. Scholer , Vol. 45, 341--367
work page 2013
- [6]
-
[7]
Barreto-Mota , L., de Gouveia Dal Pino , E. M., Xu , S., & Lazarian , A. 2024, arXiv e-prints, ApJ in press, arXiv:2405.12146
-
[8]
Beg, R., Russell, A. J., & Hornig, G. 2022, The Astrophysical Journal, 940, 94
work page 2022
- [9]
- [10]
-
[11]
Cerutti , B., Uzdensky , D. A., & Begelman , M. C. 2012, , 746, 148
work page 2012
-
[12]
Cerutti , B., Werner , G. R., Uzdensky , D. A., & Begelman , M. C. 2013, , 770, 147
work page 2013
- [13]
-
[14]
2012, in High Performance Visualization--Enabling Extreme-Scale Scientific Insight, 357--372
Childs, H., Brugger, E., Whitlock, B., et al. 2012, in High Performance Visualization--Enabling Extreme-Scale Scientific Insight, 357--372
work page 2012
-
[15]
M., Petropoulou , M., Sironi , L., & Giannios , D
Christie , I. M., Petropoulou , M., Sironi , L., & Giannios , D. 2019, , 482, 65
work page 2019
- [16]
- [17]
- [18]
-
[19]
de Gouveia Dal Pino , E. M., & Kowal , G. 2015, Astrophysics and Space Science Library, Vol. 407, Particle Acceleration by Magnetic Reconnection , ed. A. Lazarian , E. M. de Gouveia Dal Pino , & C. Melioli (Springer Berlin Heidelberg), 373
work page 2015
-
[20]
de Gouveia Dal Pino , E. M., Kowal , G., Kadowaki , L. H. S., Piovezan , P., & Lazarian , A. 2010 a , International Journal of Modern Physics D, 19, 729
work page 2010
- [21]
-
[22]
de Gouveia Dal Pino , E. M., Piovezan , P. P., & Kadowaki , L. H. S. 2010 b , A&A, 518, 5
work page 2010
-
[23]
M., Rodr \' guez-Ram \' rez , J
de Gouveia Dal Pino , E. M., Rodr \' guez-Ram \' rez , J. C., & del Valle , M. V. 2025, , 537, 3895
work page 2025
-
[24]
del Valle , M. V., de Gouveia Dal Pino , E. M., & Kowal , G. 2016, , 463, 4331
work page 2016
-
[25]
F., Opher , M., Swisdak , M., & Chamoun , J
Drake , J. F., Opher , M., Swisdak , M., & Chamoun , J. N. 2010, , 709, 963
work page 2010
-
[26]
F., Swisdak , M., Che , H., & Shay , M
Drake , J. F., Swisdak , M., Che , H., & Shay , M. A. 2006, , 443, 553
work page 2006
- [27]
-
[28]
Giannios , D., Uzdensky , D. A., & Begelman , M. C. 2009, , 395, L29
work page 2009
-
[29]
2016, Physics of Plasmas, 23, 055708
Guo , F., Li , H., Daughton , W., Li , X., & Liu , Y.-H. 2016, Physics of Plasmas, 23, 055708
work page 2016
- [30]
- [31]
-
[32]
2020, Physics of Plasmas, 27, 080501
Guo , F., Liu , Y.-H., Li , X., et al. 2020, Physics of Plasmas, 27, 080501
work page 2020
- [33]
- [34]
-
[35]
2016, The Astrophysical Journal, 818, 20
Huang, Y.-M., & Bhattacharjee, A. 2016, The Astrophysical Journal, 818, 20. https://dx.doi.org/10.3847/0004-637X/818/1/20
-
[36]
T., Kowal , G., & Lazarian , A
Jafari , A., Vishniac , E. T., Kowal , G., & Lazarian , A. 2018, , 860, 52
work page 2018
-
[37]
Kadowaki , L. H. S., de Gouveia Dal Pino , E. M., Medina-Torrej \'o n , T. E., Mizuno , Y., & Kushwaha , P. 2021, , 912, 109
work page 2021
-
[38]
Kadowaki , L. H. S., de Gouveia Dal Pino , E. M., & Singh , C. B. 2015, , 802, 113
work page 2015
-
[39]
Kadowaki, L. H. S., de Gouveia Dal Pino, E. M., & Stone, J. M. 2018, The Astrophysical Journal, 864, 52. https://dx.doi.org/10.3847/1538-4357/aad4ff
- [40]
-
[41]
Kowal , G., de Gouveia Dal Pino , E. M., & Lazarian , A. 2011, , 735, 102
work page 2011
- [42]
-
[43]
A., Lazarian , A., & Vishniac , E
Kowal , G., Falceta-Gon c alves , D. A., Lazarian , A., & Vishniac , E. T. 2020, , 892, 50
work page 2020
-
[44]
Kowal , G., Lazarian , A., Vishniac , E. T., & Otmianowska-Mazur , K. 2009, ApJ, 700, 63
work page 2009
-
[45]
Lazarian , A., Eyink , G. L., Jafari , A., et al. 2020, Physics of Plasmas, 27, 012305
work page 2020
-
[46]
Lazarian , A., & Vishniac , E. T. 1999, , 517, 700
work page 1999
- [47]
- [48]
-
[49]
2021, Physics of Plasmas, 28, 052905
Li , X., Guo , F., & Liu , Y.-H. 2021, Physics of Plasmas, 28, 052905
work page 2021
- [50]
- [51]
-
[52]
2018, Journal of Plasma Physics, 84, 635840201
Lyutikov , M., Komissarov , S., Sironi , L., & Porth , O. 2018, Journal of Plasma Physics, 84, 635840201
work page 2018
-
[53]
Lyutikov , M., Sironi , L., Komissarov , S. S., & Porth , O. 2017, Journal of Plasma Physics, 83, 635830602
work page 2017
- [54]
-
[55]
Medina-Torrej \'o n , T. E., de Gouveia Dal Pino , E. M., Kadowaki , L. H. S., et al. 2021, , 908, 193
work page 2021
-
[56]
Medina-Torrej \'o n , T. E., de Gouveia Dal Pino , E. M., & Kowal , G. 2023, , 952, 168
work page 2023
- [57]
-
[58]
Murase , K., Mukhopadhyay , M., Kheirandish , A., Kimura , S. S., & Fang , K. 2022, , 941, L10
work page 2022
- [59]
- [60]
-
[61]
Ripperda , B., Porth , O., Xia , C., & Keppens , R. 2017, , 471, 3465
work page 2017
-
[62]
Santos-Lima , R., Guerrero , G., de Gouveia Dal Pino , E. M., & Lazarian , A. 2020, arXiv e-prints, arXiv:2005.07775
-
[63]
Santos-Lima , R., Lazarian , A., de Gouveia Dal Pino , E. M., & Cho , J. 2010, , 714, 442
work page 2010
-
[64]
Singh , C. B., de Gouveia Dal Pino , E. M., & Kadowaki , L. H. S. 2015, , 799, L20
work page 2015
-
[65]
B., Mizuno , Y., & de Gouveia Dal Pino , E
Singh , C. B., Mizuno , Y., & de Gouveia Dal Pino , E. M. 2016, , 824, 48
work page 2016
- [66]
- [67]
- [68]
- [69]
-
[70]
Van Rossum, G., & Drake, F. L. 2009, Python 3 Reference Manual (Scotts Valley, CA: CreateSpace)
work page 2009
-
[71]
H., Kowal , G., de Gouveia Dal Pino , E
Vicentin , G. H., Kowal , G., de Gouveia Dal Pino , E. M., & Lazarian , A. 2024, arXiv e-prints, ApJ in press, arXiv:2405.15909
- [72]
-
[73]
Werner , G. R., Philippov , A. A., & Uzdensky , D. A. 2019, , 482, L60
work page 2019
-
[74]
Werner , G. R., Uzdensky , D. A., Begelman , M. C., Cerutti , B., & Nalewajko , K. 2018, , 473, 4840
work page 2018
- [75]
-
[76]
Yuan , Y., Nalewajko , K., Zrake , J., East , W. E., & Blandford , R. D. 2016, , 828, 92
work page 2016
- [77]
- [78]
- [79]
- [80]
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.