BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:The inefficiency of the first-order Fermi process in UHECR product ion at relativistic shocks DTSTART;VALUE=DATE-TIME:20070705T170500Z DTEND;VALUE=DATE-TIME:20070705T171700Z DTSTAMP;VALUE=DATE-TIME:20260418T194953Z UID:indico-contribution-90-0-1051@cern.ch DESCRIPTION:Speakers: Dr. NIEMIEC\, Jacek (Iowa State University\, Ames\, IA\, USA and Institute of Nuclear Physics PAN\, Krakow\, Poland)\nThe que stion of the origin of ultra-high-energy cosmic rays at relativistic shock \nwaves is discussed in the light of results of recent Monte Carlo studies of the\nfirst-order Fermi particle acceleration (Niemiec & Ostrowski 2006 \; Niemiec\, Ostrowski\n& Pohl 2006). The models of the turbulent magnetic field near the shock considered in\nthese simulations include realistic f eatures of the perturbed magnetic field\nstructures at the shock\, which a llow us to study all the field and particle motion\ncharacteristics that a re important for cosmic-ray acceleration. Our results show that\nturbulent conditions near the shock\, that are consistent with the shock jump\ncond itions\, lead to substantial modifications of the acceleration process wit h\nrespect to the simplified models\, that produce wide-range power-law en ergy\ndistributions\, often with \nthe "universal" spectral index. Relativ istic shocks are essentially always\nsuperluminal\, and thus they preferen tially generate steep particle spectra with\ncutoffs well below the maximu m scattering energy\, often not exceeding the energy of\nthe compressed ba ckground plasma ions. Thus\, cosmic-ray acceleration to very high\nenergie s at relativistic shock waves is inefficient\, and such shocks are not exp ected\nto be the sources of ultra-high-energy particles.\n\nhttps://indico .nucleares.unam.mx/event/4/session/90/contribution/1051 LOCATION:Merida\, Mexico Uxmal + Tulum (Holiday Inn) URL:https://indico.nucleares.unam.mx/event/4/session/90/contribution/1051 END:VEVENT BEGIN:VEVENT SUMMARY:Particle acceleration by multiple parallel shocks DTSTART;VALUE=DATE-TIME:20070705T171700Z DTEND;VALUE=DATE-TIME:20070705T172900Z DTSTAMP;VALUE=DATE-TIME:20260418T194953Z UID:indico-contribution-90-0-475@cern.ch DESCRIPTION:Speakers: Dr. TAMMI\, Joni (University College Dublin)\nWe pre sent both numerical and semi-analytical results on test-particle\naccelera tion in multiple parallel shocks. We apply a kinetic Monte Carlo\ncode and an eigenfunction expansion method to calculate the\ndistribution function s for electron populations accelerated in \nsubsequent parallel shocks wit h thickness varying from infinitely thin\nsteps to broader modified struct ures\, for shock speeds ranging from non-\nto ultra-relativistic. We exami ne the levels of particle anisotropy at\nthe shocks and produce sample syn chrotron spectra. We discuss the\nimplications for AGN and microquasar jet s.\n\nhttps://indico.nucleares.unam.mx/event/4/session/90/contribution/475 LOCATION:Merida\, Mexico Uxmal + Tulum (Holiday Inn) URL:https://indico.nucleares.unam.mx/event/4/session/90/contribution/475 END:VEVENT BEGIN:VEVENT SUMMARY:Theory of nonlinear particle acceleration at shocks and self-gener ation of the magnetic field DTSTART;VALUE=DATE-TIME:20070705T174100Z DTEND;VALUE=DATE-TIME:20070705T175300Z DTSTAMP;VALUE=DATE-TIME:20260418T194953Z UID:indico-contribution-90-0-341@cern.ch DESCRIPTION:Speakers: Dr. BLASI\, Pasquale (INAF/Osservatorio Astrofisico di Arcetri & INFN L'Aquila)\nWe present some recent developments in the th eory of particle acceleration at shock\nfronts in the presence of dynamica l reaction of the accelerated particles and\nself-generation of magnetic f ield due to streaming instability. The spectra of\naccelerated particles\, the velocity\, magnetic field and temperature profiles can be\ncalculated in this approach anywhere in the precursor and in the downstream region.\ nThe implications for the origin of cosmic rays and for the phenomenology of supernova\nremnants will be discussed.\n\nhttps://indico.nucleares.unam .mx/event/4/session/90/contribution/341 LOCATION:Merida\, Mexico Uxmal + Tulum (Holiday Inn) URL:https://indico.nucleares.unam.mx/event/4/session/90/contribution/341 END:VEVENT BEGIN:VEVENT SUMMARY:Magnetic trapping acceleration in interplanetary plasmas DTSTART;VALUE=DATE-TIME:20070705T175300Z DTEND;VALUE=DATE-TIME:20070705T180500Z DTSTAMP;VALUE=DATE-TIME:20260418T194953Z UID:indico-contribution-90-0-436@cern.ch DESCRIPTION:Speakers: Prof. TAKEUCHI\, Satoshi (University of Yamanashi)\n The magnetic trapping acceleration is a new type of particle trapping and \nacceleration in which\, in principle\, test particles are accelerated in definitely. A \nmodel of magnetized plasma clouds is used to simulate a s hock-type wave. \nThe attainable energies of test particles trapped by th e moving magnetic \nneutral sheets are investigated by analytical and nume rical methods. To \naccount for the high energy of cosmic rays\, this mec hanism would make an \nimportant role in magnetic field reconnections and shock surfing accelerations in \ninterplanetary plasmas.\n\nhttps://indico .nucleares.unam.mx/event/4/session/90/contribution/436 LOCATION:Merida\, Mexico Uxmal + Tulum (Holiday Inn) URL:https://indico.nucleares.unam.mx/event/4/session/90/contribution/436 END:VEVENT BEGIN:VEVENT SUMMARY:Magnetic turbulence production by streaming cosmic rays upstream o f SNR shocks DTSTART;VALUE=DATE-TIME:20070705T180500Z DTEND;VALUE=DATE-TIME:20070705T181700Z DTSTAMP;VALUE=DATE-TIME:20260418T194953Z UID:indico-contribution-90-0-1047@cern.ch DESCRIPTION:Speakers: Dr. NIEMIEC\, Jacek (Iowa State University\, Ames\, IA\, USA and Institute of Nuclear Physics PAN\, Krakow\, Poland)\nWe pres ent preliminary results of Particle-In-Cell simulations of magnetic turbul ence\nproduction by isotropic cosmic ray nucleons streaming upstream of su pernova remnant\nshocks. The studies aim at testing the MHD predictions by Bell (2004\, 2005) of a\nstrong amplification of short-wavelength nonreso nant wave modes and at studying the\nthe subsequent evolution of the magne tic turbulence and its backreaction on cosmic\nray trajectories. The detai led knowledge of the upstream turbulence properties is\ncrucial to ascerta in all aspects of the shock acceleration process - the transport\nproperti es of cosmic rays\, the shock structure\, thermal particle injection and\n heating processes. An amplification of magnetic field would also facilitat e the\nacceleration of particles beyond the "knee" in the cosmic-ray spect rum. Our kinetic\napproach is particularly suited to address the backreact ion on the cosmic rays\, and\nit allows us to test Bell's prediction of th e eventual formation of extended\nfilamentary structure in the cosmic-ray distribution and also to arrive at a reliable\nestimate of the total satur ation magnetic-field level. The parameters chosen for the\nsimulations are favorable for the rapid excitation of purely growing modes. However\,\nno significant magnetic turbulence build-up is observed. This suggests that the\ngrowth of the turbulent magnetic field is slower than estimated using the MHD\napproach. We compare these results with a model in which a beam of cosmic-ray nuleons\nis streaming in the upstream plasma\, in which case we observe the production of\nstrong magnetic turbulence in the plane per pendicular to the streaming direction.\nQuantitative differences between b oth scenarios are discussed.\n\nhttps://indico.nucleares.unam.mx/event/4/s ession/90/contribution/1047 LOCATION:Merida\, Mexico Uxmal + Tulum (Holiday Inn) URL:https://indico.nucleares.unam.mx/event/4/session/90/contribution/1047 END:VEVENT BEGIN:VEVENT SUMMARY:Effects of Large-Scale Upstream Turbulence on a Supernova Blast Wa ve \nand Energetic Particles DTSTART;VALUE=DATE-TIME:20070705T181700Z DTEND;VALUE=DATE-TIME:20070705T182900Z DTSTAMP;VALUE=DATE-TIME:20260418T194953Z UID:indico-contribution-90-0-78@cern.ch DESCRIPTION:Speakers: Prof. JOKIPII\, Jack (Randy) (University of Arizona) \nWe consider the effect of pre-existing turbulent fluctuations \nin the f luid upstream of a propagating hydromagnetic \nshock wave\, in the limit o f high enough Alf\\'en mach \nnumber that the magnetic field stresses can be neglected. \nWe find the expected effects on transverse diffusion\, an d\nshow that particles can be readily accelerated up to the \nknee in the spectrum at a perpendicular shock. \nWe also find that pre-existing turbu lent density \nfluctuations not only distort the shock front\, but also \ nproduce a number of changes in the postshock fluid\, the most \nnoteworth y of which are to the postshock magnetic field. The \naverage magnetic-f ield intensity is increased siginificantly\, \nand large fluctuations in t he magnetic vector occur. Also\, for a \nradially propagating blast wave\ , we show that the large radial \nexpansion of the postshock fluid \ncause s the magnetic field to have a predominantly radial \norientation (either outward or inward). These effects of the \ndensity fluctuations are simi lar to those observed in strong \nastrophysical shock waves and suggest t hat the density fluctuations \nmay play an important and possibly dominant role in creating the \nobserved properties of astrophysical shocks.\n\nht tps://indico.nucleares.unam.mx/event/4/session/90/contribution/78 LOCATION:Merida\, Mexico Uxmal + Tulum (Holiday Inn) URL:https://indico.nucleares.unam.mx/event/4/session/90/contribution/78 END:VEVENT END:VCALENDAR