Rafael Alves Batista

Diffusion of cosmic rays at EeV energies in inhomogeneous extragalactic magnetic fields

Abstract. Ultra-highenergycosmicrayscanpropagatediffusivelyincosmicmagneticfields.Whentheirpropagationtimeiscomparabletotheageoftheuniverse,asuppressioninthefluxrelativetothecaseintheabsenceofmagneticfieldswilloccur. Inthisworkwefindanapproximate parametrization for this suppression at energies below ˘Z EeV using severalmagneticfielddistributionsobtainedfromcosmologicalsimulationsofthemagnetizedcosmicweb. WeassumethatthemagneticfieldshaveaKolmogorovpowerspectrumwiththefieldstrengths distributed according to these simulations. We show that, if magnetic fields arecoupled to the matter distribution, low field strengths will fill most of the volume, makingthesuppressionmildercomparedtothecaseofaconstantmagneticfieldwithstrengthequalto the mean value of this distribution. We also derive upper limits for this suppression tooccurforsomemodelsofextragalacticmagneticfields,asafunctionofthecoherencelengthofthesefields. arXiv:1407.6150v1 [astro-ph.HE] 23 Jul 2014 Keywords: extragalacticmagneticfields,cosmicraytheory,cosmicweb

Ultrahigh-energy cosmic rays from tidally-ignited white dwarfs

Ultrahigh-energy cosmic rays (UHECRs) can be accelerated by tidal disruption events of stars by black holes. We suggest a novel mechanism for UHECR acceleration wherein white dwarfs (WDs) are tidally compressed by intermediate-mass black holes (IMBHs), leading to their ignition and subsequent explosion as a supernova. Cosmic rays accelerated by the supernova may receive an energy boost when crossing the accretion-powered jet. The rate of encounters between WDs and IMBHs can be relatively high, as the number of IMBHs may be substantially augmented once account is taken of their likely presence in dwarf galaxies. Here we show that this kind of tidal disruption event naturally provides an intermediate composition for the observed UHECRs, and suggest that dwarf galaxies and globular clusters are suitable sites for particle acceleration to ultrahigh energies.

Implications of strong intergalactic magnetic fields for ultrahigh-energy cosmic-ray astronomy

We study the propagation of ultra-high-energy cosmic rays in the magnetised cosmic web. We focus on the particular case of highly magnetised voids (

Cosmogenic gamma-rays and neutrinos constrain UHECR source models

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Propagation of UHECRs in the universe

), using the upper bounds from the Planck satellite. The cosmic web was obtained from purely magnetohydrodynamical cosmological simulations of structure formation considering different power spectra for the seed magnetic field in order to account for theoretical uncertainties. We investigate the impact of these uncertainties on the propagation of cosmic rays, showing that they can affect the measured spectrum and composition by up to

The Giant Radio Array for Neutrino Detection (GRAND) : Present and Perspectives

simeq 80%

Magnetic horizons of ultra-high energy cosmic rays

and

Amplification of the Signal-to-Noise Ratio in Cosmic Ray Map s Using the Mexican Hat Wavelet Family

simeq 5%

CRPropa 3.0 – a Public Framework for Propagating UHE Cosmic Rays through Galactic and Extragalactic Space

, respectivelly. In our scenarios, even if magnetic fields in voids are strong, deflections of 50 EeV protons from sources closer than

Ultra-high-energy cosmic rays from tidally-ignited stars

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