Effects of Compton Scattering on the Gamma-Ray Spectra of Solar Flares

[摘要] UsingthefullyrelativisticGEANT4simulationtoolkit,MonteCarlosimulationwasappliedtothetransportofenergeticelectronsgeneratedinsolarflares,andresultantbremsstrahlunggamma-rayspectrawerecalculated.Thesolaratmospherewasapproximatedby10verticallystackedzones.Thesimulationtookintoaccounttwoimportantphysicalprocesses:thatthebremsstrahlungphotonsemittedbyprecipitatingrelativisticelectronsarestronglyforwardbeamedtowardthephotosphere,andthatthemajorityofthesegamma-raysmustbeComptonbackscatteredbythesolaratmosphereinordertoreachtheobserver.Then,theComptondegradationwasfoundtomaketheobservablegamma-rayspectramuchsofterthanpredictedbysimpleanalyticcalculations.Thegamma-raysignalswerefoundtobeenhancedbyseveralconditions,includingabroadpitch-angledistributionoftheelectrons,anear-limbflarelongitude,andasignificanttiltinthemagneticfieldlinesiftheflarelongitudeisrathersmall.TheseresultssuccessfullyexplainseveralimportantflarepropertiesobservedintherangeofhardX-raytogamma-ray,inparticularincludingthoseobtainedwithYohkoh.AcomparisonoftheYohkohspectrum,fromaGOESX3.7classlimbflareon1998November22,withasimulationassumingabroadelectronpitch-angledistributionsuggeststhatgamma-raysfromthisparticularsolarflarewereamixtureofdirectbremsstrahlungphotonsandtheirComptonization.

[学科分类] 天文学(综合)

[关键词] "scattering: Compton scattering";"Sun: flares";"Sun: gamma rays"