Dynamics of rising magnetized cavities and UHECR acceleration in clusters of galaxies

Abstract

We study the expansion of low density cavities produced by Active Galactic Nuclei jets in clusters of galaxies. The long term stability of these cavities requires the presence of linked magnetic fields. We find solutions describing the self-similar expansion of structures containing large-scale electromagnetic fields. Unlike the force-free spheromak-like configurations, these solutions have no surface currents and, thus, are less susceptible to resistive decay. The cavities are internally confined by external pressure, with zero gradient at the surface. If the adiabatic index of the plasma within the cavity is $\Gamma >4/3$, the expansion ultimately leads to the formation of large-scale current sheets. The resulting dissipation of the magnetic field can only partially offset the adiabatic and radiative losses of radio emitting electrons. We demonstrate that if the formation of large-scale current sheets is accompanied by explosive reconnection of the magnetic field, the resulting reconnection layer can accelerate cosmic rays to ultra high energies. We speculate that the enhanced flux of UHECRs towards Centaurus A originates at the cavities due to magnetic reconnection.

9 pages

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Cited by in corpus (7)

• Suzaku observations of the diffuse x-ray emission across the fermi bubbles' edges
• Non-Thermal Insights on Mass and Energy Flows Through the Galactic Centre and into the Fermi Bubbles
• Hall equilibria with toroidal and poloidal fields: application to neutron stars
• Giant Lobes of Centaurus A Radio Galaxy Observed with the Suzaku X-ray Satellite
• The Dynamic Age of Centaurus A
• Galactic winds - How to launch galactic outflows in typical Lyman-break galaxies
• Relativistic magnetic explosions