Issue |
A&A
Volume 683, March 2024
|
|
---|---|---|
Article Number | A69 | |
Number of page(s) | 13 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361/202348087 | |
Published online | 08 March 2024 |
Streaming instability in neutron star magnetospheres: No indication of soliton-like waves⋆
1
Institute for Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany
e-mail: jan.benacek@uni-potsdam.de
2
Center for Astronomy and Astrophysics, Technical University of Berlin, 10623 Berlin, Germany
3
Max Planck Institute for Solar System Research, 37077 Göttingen, Germany
4
Max-Planck Institute for Radio Astronomy, 53121 Bonn, Germany
Received:
27
September
2023
Accepted:
12
December
2023
Context. Coherent radiation of pulsars, magnetars, and fast radio bursts could, in theory, be interpreted as radiation from solitons and soliton-like waves. Solitons are meant to contain a large number of electric charges confined on long timescales and can radiate strongly via coherent curvature emission. However, solitons are also known to undergo a wave collapse, which casts doubts on the correctness of the soliton radio emission models of neutron stars.
Aims. We investigated the evolution of the caviton type of solitons self-consistently formed by the relativistic streaming instability and compared their apparent stability in 1D calculations with more generic 2D cases, in which the solitons are seen to collapse. Three representative cases of beam Lorentz factors and plasma temperatures were studied to obtain soliton dispersion properties.
Methods. We utilized 1D electrostatic and 2D electromagnetic relativistic particle-in-cell simulations at kinetic microscales.
Results. We find that no solitons are generated by the streaming instability in the 2D simulations. Only superluminal L-mode (relativistic Langmuir) waves are produced during the saturation of the instability, but these waves have smaller amplitudes than the waves in the 1D simulations. The amplitudes tend to decrease after the instability has saturated, and only waves close to the light line, ω = ck, remain. Solitons in the 1D approach are stable for γb ≳ 60, but they disappear for low beam Lorentz factors, γb < 6.
Conclusions. Our examples show that the superluminal soliton branch that is formed in 1D simulations will not be generated by the relativistic streaming instability when more dimensional degrees of freedom are present. The soliton model cannot, therefore, be used to explain the coherent radiation of pulsars, magnetars, and fast radio bursts – unless one can show that there are alternative plasma mechanisms for the soliton generation.
Key words: instabilities / plasmas / relativistic processes / methods: numerical / stars: neutron / pulsars: general
Movie associated to Fig. 5 is available at https://www.aanda.org.
© The Authors 2024
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.
This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.