Propagation of Ultra-High Energy Cosmic Rays from Sources in the Super-Galactic Plane

摘要

WehaveperformeddetailednumericalsimulationsonthepropagationofUHEprotonsintheenergyrange$$E=(10^{19.5}hbox{--}10^{22.0}),mathrm{eV}$$inarelativelystrongextragalacticmagneticfieldwithastrengthof$$B=(10hbox{--}100),mathrm{nG}$$withinabout40Mpc.Inthiscase,thedeflectionanglesofUHECRsbecomesolargethatthenocounterpartsproblemcanbesimplysolved.Asforthesourcedistribution,weassumedthatitisproportionaltothenumberdistributionofgalaxieswithintheGreisena€“Zatsepina€“Kuzminsphere.Wefoundmanyclusters,meaningsmall-scaleanisotropy,inoursimulations.Ithasalsobeenshownthattheobservedenergyspectrumiswellreproducedinourmodelswithoutanyfine-tunedparameter.WeusedthecorrelationvalueinordertoinvestigatestatisticallythesimilaritybetweenthedistributionofarrivaldirectionsofUHECRsandthatofgalaxies.Wefoundthateachcorrelationvalueforeachparametersetbeginstoconvergewhenthenumberofdetectedeventsbecomes$$O(10^3)$$.Sincetheexpectednumbercountsbytheexperimentofthenextgeneration,suchasTA,HiRes,Auger,andEUSO,arethoughttobeontheorderof$$10^3$$,wewillbeabletocheckintheverynearfuturewhetherthesourcedistributionofUHECRsiscorrelatedwiththeSuper-GalacticPlaneornot.ComparedwiththeAGASAdata,asignificantanisotropyonthearrivaldirectionsofUHECRsisfoundintheanalysesofthefirstandsecondharmonics.ThismayoriginatefromanincompletenessoftheORSdatabase.Thisproblemmayalsobesolvedifthesourcedistributionisslightlychanged.Forexample,thisproblemmaybesolvedifweassumethatUHECRscomefromsomegalaxies,suchasAGNsandradiogalaxies.