Quasi-perpendicular shocks of galaxy clusters in hybrid kinetic simulations : the structure of the shocks

2024
journal article
article
dc.abstract.enContext. Cosmic ray acceleration in galaxy clusters is still an ongoing puzzle, with relativistic electrons forming radio relics at merger shocks and emitting synchrotron radiation. These shocks are also potential sources of ultra-high-energy cosmic rays, gamma rays, and neutrinos. Our recent work focuses on electron acceleration at low Mach number merger shocks in the hot intracluster medium which is characterized by high plasma beta. Using particle-in-cell (PIC) simulations, we previously showed that electrons are energized through the stochastic shock-drift acceleration process, which is facilitated by multi-scale turbulence, including ion-scale shock surface rippling. For the present work, we performed hybrid-kinetic simulations in a range of various quasi-perpendicular foreshock conditions, including plasma beta, magnetic obliquity, and the shock Mach number. Aims. We study the ion kinetic physics, which is responsible for the shock structure and wave turbulence, that in turn affects the particle acceleration processes. We cover the spatial and temporal scales, which allow the development of large-scale ion turbulence modes in the system. Methods. We applied a recently developed generalized fluid-particle hybrid numerical code that can combine fluid modeling for both electrons and ions with an arbitrary number of kinetic species. We limited this model to a standard hybrid simulation configuration with kinetic ions and fluid electrons. The model utilizes the exact form of the generalized Ohm’s law, allowing for an arbitrary choice of mass and energy densities, as well as the charge-to-mass ratio of the kinetic species. Results. We show that the properties of ion-driven multi-scale magnetic turbulence in merger shocks are in agreement with the ion structures observed in PIC simulations. In typical shocks with the sonic Mach number M$_{s}$ = 3, the magnetic structures and shock front density ripples grow and saturate at wavelengths reaching approximately four ion Larmor radii. Only shocks with M$_{s}$ ≳ 2.3 develop ripples. At very weak shocks with M$_{s}$ ≲ 2.3, weak turbulence is formed downstream of the shock. We observed a moderate dependence of the strength of magnetic field fluctuations on the quasi-perpendicular magnetic field obliquity. However, as the field obliquity decreases, the shock front ripples exhibit longer wavelengths. Finally, we note that the steady-state structure of M$_{s}$ = 3 shocks in high-beta plasmas shows evidence that there is little difference between 2D and 3D simulations. The turbulence near the shock front seems to be a 2D-like structure in 3D simulations.
dc.affiliationWydział Fizyki, Astronomii i Informatyki Stosowanej : Instytut – Obserwatorium Astronomiczne
dc.contributor.authorBoula, S. S.
dc.contributor.authorNiemiec, J.
dc.contributor.authorAmano, T.
dc.contributor.authorKobzar, Oleh - 428622
dc.date.accessioned2024-04-19T09:44:37Z
dc.date.available2024-04-19T09:44:37Z
dc.date.issued2024
dc.date.openaccess0
dc.description.accesstimew momencie opublikowania
dc.description.versionostateczna wersja wydawcy
dc.description.volume684
dc.identifier.articleidA129
dc.identifier.doi10.1051/0004-6361/202349091
dc.identifier.eissn1432-0746
dc.identifier.issn0004-6361
dc.identifier.urihttps://ruj.uj.edu.pl/handle/item/330596
dc.languageeng
dc.language.containereng
dc.rightsUdzielam licencji. Uznanie autorstwa 4.0 Międzynarodowa
dc.rights.licenceCC-BY
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/legalcode.pl
dc.share.typeotwarte czasopismo
dc.subject.eninstabilities
dc.subject.enplasmas
dc.subject.enshock waves
dc.subject.enturbulence
dc.subject.enmethods: numerical
dc.subject.engalaxies: clusters: general
dc.subtypeArticle
dc.titleQuasi-perpendicular shocks of galaxy clusters in hybrid kinetic simulations : the structure of the shocks
dc.title.journalAstronomy and Astrophysics
dc.typeJournalArticle
dspace.entity.typePublicationen
dc.abstract.en
Context. Cosmic ray acceleration in galaxy clusters is still an ongoing puzzle, with relativistic electrons forming radio relics at merger shocks and emitting synchrotron radiation. These shocks are also potential sources of ultra-high-energy cosmic rays, gamma rays, and neutrinos. Our recent work focuses on electron acceleration at low Mach number merger shocks in the hot intracluster medium which is characterized by high plasma beta. Using particle-in-cell (PIC) simulations, we previously showed that electrons are energized through the stochastic shock-drift acceleration process, which is facilitated by multi-scale turbulence, including ion-scale shock surface rippling. For the present work, we performed hybrid-kinetic simulations in a range of various quasi-perpendicular foreshock conditions, including plasma beta, magnetic obliquity, and the shock Mach number. Aims. We study the ion kinetic physics, which is responsible for the shock structure and wave turbulence, that in turn affects the particle acceleration processes. We cover the spatial and temporal scales, which allow the development of large-scale ion turbulence modes in the system. Methods. We applied a recently developed generalized fluid-particle hybrid numerical code that can combine fluid modeling for both electrons and ions with an arbitrary number of kinetic species. We limited this model to a standard hybrid simulation configuration with kinetic ions and fluid electrons. The model utilizes the exact form of the generalized Ohm’s law, allowing for an arbitrary choice of mass and energy densities, as well as the charge-to-mass ratio of the kinetic species. Results. We show that the properties of ion-driven multi-scale magnetic turbulence in merger shocks are in agreement with the ion structures observed in PIC simulations. In typical shocks with the sonic Mach number M$_{s}$ = 3, the magnetic structures and shock front density ripples grow and saturate at wavelengths reaching approximately four ion Larmor radii. Only shocks with M$_{s}$ ≳ 2.3 develop ripples. At very weak shocks with M$_{s}$ ≲ 2.3, weak turbulence is formed downstream of the shock. We observed a moderate dependence of the strength of magnetic field fluctuations on the quasi-perpendicular magnetic field obliquity. However, as the field obliquity decreases, the shock front ripples exhibit longer wavelengths. Finally, we note that the steady-state structure of M$_{s}$ = 3 shocks in high-beta plasmas shows evidence that there is little difference between 2D and 3D simulations. The turbulence near the shock front seems to be a 2D-like structure in 3D simulations.
dc.affiliation
Wydział Fizyki, Astronomii i Informatyki Stosowanej : Instytut – Obserwatorium Astronomiczne
dc.contributor.author
Boula, S. S.
dc.contributor.author
Niemiec, J.
dc.contributor.author
Amano, T.
dc.contributor.author
Kobzar, Oleh - 428622
dc.date.accessioned
2024-04-19T09:44:37Z
dc.date.available
2024-04-19T09:44:37Z
dc.date.issued
2024
dc.date.openaccess
0
dc.description.accesstime
w momencie opublikowania
dc.description.version
ostateczna wersja wydawcy
dc.description.volume
684
dc.identifier.articleid
A129
dc.identifier.doi
10.1051/0004-6361/202349091
dc.identifier.eissn
1432-0746
dc.identifier.issn
0004-6361
dc.identifier.uri
https://ruj.uj.edu.pl/handle/item/330596
dc.language
eng
dc.language.container
eng
dc.rights
Udzielam licencji. Uznanie autorstwa 4.0 Międzynarodowa
dc.rights.licence
CC-BY
dc.rights.uri
http://creativecommons.org/licenses/by/4.0/legalcode.pl
dc.share.type
otwarte czasopismo
dc.subject.en
instabilities
dc.subject.en
plasmas
dc.subject.en
shock waves
dc.subject.en
turbulence
dc.subject.en
methods: numerical
dc.subject.en
galaxies: clusters: general
dc.subtype
Article
dc.title
Quasi-perpendicular shocks of galaxy clusters in hybrid kinetic simulations : the structure of the shocks
dc.title.journal
Astronomy and Astrophysics
dc.type
JournalArticle
dspace.entity.typeen
Publication
Affiliations

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