Synchrotron Firehose Instability
We demonstrate using linear theory and particle-in-cell (PIC) simulations that a synchrotron-cooling collisionless plasma acquires pressure anisotropy and, if the plasma beta is sufficiently high, becomes unstable to the firehose instability, in a process that we dub the synchrotron firehose instabi...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/acaf54 |
| _version_ | 1797702090346201088 |
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| author | Vladimir Zhdankin Matthew W. Kunz Dmitri A. Uzdensky |
| author_facet | Vladimir Zhdankin Matthew W. Kunz Dmitri A. Uzdensky |
| author_sort | Vladimir Zhdankin |
| collection | DOAJ |
| description | We demonstrate using linear theory and particle-in-cell (PIC) simulations that a synchrotron-cooling collisionless plasma acquires pressure anisotropy and, if the plasma beta is sufficiently high, becomes unstable to the firehose instability, in a process that we dub the synchrotron firehose instability (SFHI). The SFHI channels free energy from the pressure anisotropy of the radiating, relativistic electrons (and/or positrons) into small-amplitude, kinetic-scale, magnetic-field fluctuations, which pitch-angle scatter the particles and bring the plasma to a near-thermal state of marginal instability. The PIC simulations reveal a nonlinear cyclic evolution of firehose bursts interspersed by periods of stable cooling. We compare the SFHI for electron–positron and electron–ion plasmas. As a byproduct of the growing electron-firehose magnetic-field fluctuations, magnetized ions gain a pressure anisotropy opposite to that of the electrons. If these ions are relativistically hot, we find that they also experience cooling due to collisionless thermal coupling with the electrons, which we argue is mediated by a secondary ion-cyclotron instability. We suggest that the SFHI may be activated in a number of astrophysical scenarios, such as within ejecta from black hole accretion flows and relativistic jets, where the redistribution of energetic electrons from low to high pitch angles may cause transient bursts of radiation. |
| first_indexed | 2024-03-12T04:45:09Z |
| format | Article |
| id | doaj.art-8a5882401026455aa3becb2d44f14809 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T04:45:09Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-8a5882401026455aa3becb2d44f148092023-09-03T09:29:30ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0194412410.3847/1538-4357/acaf54Synchrotron Firehose InstabilityVladimir Zhdankin0https://orcid.org/0000-0003-3816-7896Matthew W. Kunz1https://orcid.org/0000-0003-1676-6126Dmitri A. Uzdensky2https://orcid.org/0000-0001-8792-6698Center for Computational Astrophysics, Flatiron Institute , 162 Fifth Avenue, New York, NY, 10010, USA ; vzhdankin@flatironinstitute.orgDepartment of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ, 08544, USA; Princeton Plasma Physics Laboratory , P.O. Box 451, Princeton, NJ, 08543, USACenter for Integrated Plasma Studies, Department of Physics, 390 UCB, University of Colorado , Boulder, CO, 80309, USAWe demonstrate using linear theory and particle-in-cell (PIC) simulations that a synchrotron-cooling collisionless plasma acquires pressure anisotropy and, if the plasma beta is sufficiently high, becomes unstable to the firehose instability, in a process that we dub the synchrotron firehose instability (SFHI). The SFHI channels free energy from the pressure anisotropy of the radiating, relativistic electrons (and/or positrons) into small-amplitude, kinetic-scale, magnetic-field fluctuations, which pitch-angle scatter the particles and bring the plasma to a near-thermal state of marginal instability. The PIC simulations reveal a nonlinear cyclic evolution of firehose bursts interspersed by periods of stable cooling. We compare the SFHI for electron–positron and electron–ion plasmas. As a byproduct of the growing electron-firehose magnetic-field fluctuations, magnetized ions gain a pressure anisotropy opposite to that of the electrons. If these ions are relativistically hot, we find that they also experience cooling due to collisionless thermal coupling with the electrons, which we argue is mediated by a secondary ion-cyclotron instability. We suggest that the SFHI may be activated in a number of astrophysical scenarios, such as within ejecta from black hole accretion flows and relativistic jets, where the redistribution of energetic electrons from low to high pitch angles may cause transient bursts of radiation.https://doi.org/10.3847/1538-4357/acaf54Plasma astrophysics |
| spellingShingle | Vladimir Zhdankin Matthew W. Kunz Dmitri A. Uzdensky Synchrotron Firehose Instability The Astrophysical Journal Plasma astrophysics |
| title | Synchrotron Firehose Instability |
| title_full | Synchrotron Firehose Instability |
| title_fullStr | Synchrotron Firehose Instability |
| title_full_unstemmed | Synchrotron Firehose Instability |
| title_short | Synchrotron Firehose Instability |
| title_sort | synchrotron firehose instability |
| topic | Plasma astrophysics |
| url | https://doi.org/10.3847/1538-4357/acaf54 |
| work_keys_str_mv | AT vladimirzhdankin synchrotronfirehoseinstability AT matthewwkunz synchrotronfirehoseinstability AT dmitriauzdensky synchrotronfirehoseinstability |