Issue |
A&A
Volume 661, May 2022
|
|
---|---|---|
Article Number | A130 | |
Number of page(s) | 6 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361/202243152 | |
Published online | 17 May 2022 |
Intra-pulse variability induced by plasmoid formation in pulsar magnetospheres
1
Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
e-mail: benoit.cerutti@univ-grenoble-alpes.fr
2
Istanbul Technical University, Faculty of Science and Letters, Physics Engineering Department, 34469 Istanbul, Turkey
Received:
19
January
2022
Accepted:
21
April
2022
Context. Pulsars show irregularities in their pulsed radio emission that originate from propagation effects and the intrinsic activity of the source.
Aims. In this work, we investigate the role played by magnetic reconnection and the formation of plasmoids in the pulsar wind current sheet as a possible source of intrinsic pulse-to-pulse variability in the incoherent, high-energy emission pattern.
Methods. We used a two-dimensional particle-in-cell simulation of an orthogonal pulsar magnetosphere restricted to the plane perpendicular to the star spin axis. We evolved the solution for several tens of pulsar periods to gather a statistically significant sample of synthetic pulse profiles.
Results. The formation of plasmoids leads to strong pulse-to-pulse variability in the form of multiple short, bright subpulses, which appear only on the leading edge of each main pulse. These secondary peaks of emission are dominated by the dozen plasmoids that can grow up to macroscopic scales. They emerge from the high end of the hierarchical merging process occurring along the wind current layer. The flux of the subpulses is correlated with their width in phase. Although the full-scale separation is not realistic, we argue that the simulation correctly captures the demographics and the properties of the largest plasmoids, and therefore of the brightest subpulses.
Conclusions. The prediction of subpulses at specific pulse phases provides a new observational test of the magnetic reconnection scenario as the origin of the pulsed incoherent emission. High-time-resolution observations of the Crab pulsar in the optical range may be the most promising source to target for this purpose.
Key words: pulsars: general / acceleration of particles / magnetic reconnection / radiation mechanisms: non-thermal / methods: numerical
© I. C. Andaç et al. 2022
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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