Mitsuru Honda

ULTRA-HIGH ENERGY COSMIC-RAY ACCELERATION IN THE JET OF CENTAURUS A

We evaluate the achievable maximum energy of nuclei diffusively accelerated by shock wave in the jet of Cen A, based on an updated model involving the stochastic magnetic fields that are responsible for recent synchrotron X-ray measurements. For the maximum energy analysis, conceivable energy constraints from spatiotemporal scales are systematically considered for the jet-wide including discrete X-ray knots. We find that in the inner region within ~1 arcmin from galactic core, which includes knots AX and BX, proton and iron nucleus can be accelerated to 1019-1020 and 1021 eV (10-100 EeV and ZeV) ranges, respectively. The upper cutoff energy of the very energetic neutrinos produced via photopion interaction is also provided. These are essential for identifying the acceleration site of the ultra-high energy cosmic ray detected in the Pierre Auger Observatory, which signifies the arrival from nearby galaxies including Cen A.

Self-Collimation and Magnetic Field Generation of Astrophysical Jets

A novel model for collimation and transport of electron-positron-ion jets is presented. Analytical results show that the filamentary structures can be sustained by self-induced toroidal magnetic fields permeating through the filaments, whose widths significantly expand in the pair-dominant regimes. The magnetic field strength reflects a characteristic of equipartition of excess kinetic energy of the jets. It is also shown that growth of the hoselike instability is strongly suppressed. Essential features derived from this model are consistent with recent results observed by using very long baseline telescopes.

Particle Diffusion and Acceleration by Shock Waves in Magnetized Filamentary Turbulence

We expand the off-resonant scattering theory for particle diffusion in magnetized current filaments that can be typically compared to astrophysical jets, including active galactic nucleus jets. In a high plasma β region where the directional bulk flow is a free-energy source for establishing turbulent magnetic fields via current filamentation instabilities, a novel version of quasi-linear theory to describe the diffusion of test particles is proposed. The theory relies on the proviso that the injected energetic particles are not trapped in the small-scale structure of magnetic fields wrapping around and permeating a filament but deflected by the filaments, to open a new regime of the energy hierarchy mediated by a transition compared to the particle injection. The diffusion coefficient derived from a quasi-linear type equation is applied to estimating the timescale for the stochastic acceleration of particles by the shock wave propagating through the jet. The generic scalings of the achievable highest energy of an accelerated ion and electron, as well as of the characteristic time for conceivable energy restrictions, are systematically presented. We also discuss a feasible method of verifying the theoretical predictions. The strong, anisotropic turbulence reflecting cosmic filaments might be the key to the problem of the acceleration mechanism of the highest energy cosmic rays exceeding 100 EeV (1020 eV), detected in recent air shower experiments.

Proton Acceleration beyond 100 EeV by an Oblique Shock Wave in the Jet of 3C 273

We estimate the highest energy of a proton diffusively accelerated by a shock in knot A1 of the jet in luminous nearby quasar 3C 273. Referring to the recent polarization measurements using very long baseline interferometry, we consider the shock propagation across magnetic field lines, namely, configuration of the oblique shock. For larger inclination of the field lines, the effects of particle reflection at the shock front are more pronounced, to significantly increase acceleration efficiency. The quasiperpendicular shock turns out to be needed for safely achieving the proton acceleration to the energy above 100?EeV (1020?eV) in a parameter domain reflecting conceivable energy restrictions.

On exact polytropic equilibria of self-gravitating gaseous and radiative systems: their application to molecular cloud condensation

We propose a novel mathematical method to construct an exact polytropic sphere in self-gravitating hydrostatic equilibrium, improving the non-linear Poisson equation. The central boundary condition for the present equation requires a ratio of gas pressure to total one at the centre, which is uniquely identified by the whole mass and molecular weight of the system. The special solution derived from the Lane-Emden equation can be reproduced. This scheme is now available for modelling the molecular cloud cores in interstellar media. The mass-radius relation of the first core is found to be consistent with the recent results of radiation hydrodynamic simulations.

Scalings of the synchrotron cut-off and turbulent correlation of active galactic nucleus jets

We propose a new analytic scaling of the cut-off frequency of synchrotron radiation from active galactic nucleus (AGN) jets that are non-uniformly filled with many filaments. The theoretical upper limit is provided independent of magnetic intensity, spectral index, coherence, correlation length of filamentary turbulence, etc., such that ν c ≃ 6 x 10 20 δ[(r - 1)/r] 4/3 (b/ 10- 4 ) Hz, where δ, r and b are the Doppler beaming factor, shock-compression ratio and energy-density ratio of the perturbed/local mean magnetic field of the filaments, respectively. Combining our results with observational data for 18 extragalactic sources, a constraint on the filament correlation length is found, in order to give the number scaling of filaments. The results suggest that, in particular, the jets of compact BL Lacs possess a large number of filaments with transverse size scale smaller than the emission-region size. The novel concept of the quantization of flowing plasma is suggested.

Phase-transient Hierarchical Turbulence as an Energy Correlation Generator of Blazar Light Curves

Hierarchical turbulent structure constituting a jet is considered to reproduce energy-dependent variability in blazars, particularly, the correlation between X- and gamma-ray light curves measured in the TeV blazar Markarian 421. The scale-invariant filaments are featured by the ordered magnetic fields that involve hydromagnetic fluctuations serving as electron scatterers for diffusive shock acceleration, and the spatial size scales are identified with the local maximum electron energies, which are reflected in the synchrotron spectral energy distribution (SED) above the near-infrared/optical break. The structural transition of filaments is found to be responsible for the observed change of spectral hysteresis.

Suppression of resistive hose instability in a relativistic electron-positron flow

This paper presents the effects of electron-positron pair production on the linear growth of the resistive hose instability of a filamentary beam that could lead to snake-like distortion. For both the rectangular radial density profile and the diffuse profile reflecting the Bennett-type equilibrium for a self-collimating flow, the modified eigenvalue equations are derived from a Vlasov-Maxwell equation. While for the simple rectangular profile, current perturbation is localized at the sharp radial edge, for the realistic Bennett profile with an obscure edge, it is non-locally distributed over the entire beam, removing catastrophic wave-particle resonance. The pair production effects likely decrease the betatron frequency, and expand the beam radius to increase the resistive decay time of the perturbed current; these also lead to a reduction of the growth rate. It is shown that, for the Bennett profile case, the characteristic growth distance for a preferential mode can exceed the observational length-scale of astrophysical jets. This might provide the key to the problem of the stabilized transport of the astrophysical jets including extragalactic jets up to Mpc (∼3 x 10 24 cm) scales.

Additional Acceleration of Protons and Energetic Neutrino Production in a Filamentary Jet of the Blazar Markarian 501

Blazars have been regarded as one of the most powerful sources of the highest energy cosmic rays and also their byproducts, neutrinos. Provided that a magnetized filamentary system is established in a blazar jet as well, we could apply the mechanism of multi-stage diffusive shock acceleration to a feasible TeV emitter, Mrk 501 to evaluate the achievable maximum energy of protons. Taking conceivable energy restriction into account systematically, it seems adequate to say that EeV-protons are produced at this site by our present model. We also estimate neutrino fluxes generated by these accelerated protons, and discuss the detectability based on an updated kilometer-scale telescope, such as IceCube.