time evolution of the turnover frequency for diagnosis of the coronal magnetic field

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1、TimeEvolutionoftheTurnoverFrequencyforDiagnosisoftheCoronalMagneticFieldChin.J.Astron.Astrophys.Vo1.6(2oo6),No.1,113-119(http:ffwww.chjaa.org)ChineseJournalofAstronomyandAstrophysicsTimeEvolutionoftheTurnoverFrequencyforDiagnosisoftheCoronalMagneticFieldGua

2、ng-LiHuangPurpleMountainObservatory,ChineseAcademyofSciences,Nanjing210008;glhuang@pmo.ac.cnReceived2005April26;accepted2005August30AbstractTwoimpulsivemicrowaveburstsobservedbyOwens—ValleySolarArrays(OVSA)arestudied.Thefasttimevaxiationoftheturnoverfrequen

3、cyintheseburstsisquitedifierentfromtheconstantvalueintheearlierconclusion.Theobservationalturnoverfrequenciesareconsistentwiththecalculationsusingthenon—thermalgyro-synchrotronradiationmode1.Wlefindtheturnoverfrequencymayplayanimportantroleforcalculatingthe

4、coronalmagneticfieldonthebasisofDulkandMaxsh'sap.proximations.Keywords:Sun:radioradiation—--——Sun:corona—--——Sun:magneticfields1INTR0DUCTIoNTheturnoverorpeakfrequencyisausefulquantityfordiagnosisofsolarmicrowaveandhardX-rayspectra(Dulk1985).However,insolarm

5、icrowavespectraitdoesnotshiftasexpectedduringflaredevelopmentfBenkaeta1.1992),andremainsremarkablyconstantthroughoutthedevelopmentoftheflareforthemajority(Bastianeta1.1998),whichmaybeinterpretedbyasystematicevolutionoftheelectricfieldduringthecourseofthefla

6、re,orbyRazinsuppressionwithahighambientdensityof10nam_..Ontheotherhand,thetimeevolutionoftheturnoverfrequencyhasnotbeenmuchstudiedsofar.TwoimpulsiveeventsareselectedfromtheobservationsoftheOwens—ValleySolarArraysfOVSA).andthetimeevolutionoftheturnoverfreque

7、ncyiscomparedwiththecalculationofthenon-thermalgyro—synchrotronradiationmodelinthispaper.InSection2.thetwoOVSAeventsareintroduced.Thetimeevolutionofturnoverfrequencyinthemicrowavespectraiscomparedwiththetheoreticalpredictionofanon-thermalmodelofgyro-synchro

8、tronradiationsinSection3.TheconclusionsarepresentedinSection4.2oBSERVATIoN0VSAistheonlydedicatedsolarradioobservatoryintheUSandthereforeplaysanimportantrolelnsupplyingthecommunitywithhighspatia1.tempor