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1、PreprintOctober19th2017UsingExtremeValueTheoryforDeterminingtheProbabilityofCarrington-LikeSolarFlaresS.ElvidgeandM.J.AnglingSpaceEnvironmentandRadioEngineeringGroup,UniversityofBirmingham,UK.Correspondingauthor:SeanElvidge(s.elvidge@bham.ac.uk)2017Oct
2、KeyPoints:19•ExtremevaluetheoryisappliedtoGOESX-raysolarflaredata•WorstcaseoftimescaleofCarrington-likesolarflareisshowntobe30years•Worstcaseofthelargestflareina150-yearperiodisshowntobeanX90flare[stat.AP]4AbstractBytheirverynature,extremespaceweathere
3、ventsoccurrarelyand,therefore,statisticalmethodsarerequiredtodeterminetheprobabilityoftheiroccurrence.SpaceweathereventscanbecharacterisedbyanumberofnaturalphenomenasuchasX-ray(solar)flares,solarenergeticparticle(SEP)fluxes,coronalmassejectionsandvario
4、usgeophysicalindices(Dst,Kp,F10.7).Inthispaperextremevaluetheory(EVT)isusedtoinvestigatetheprobabilityofextremesolarflares.Previousworkhasassumedthatthedistributionofsolarflaresfollowsapowerlaw.Howeversuchanapproachcanleadtoapoorestimationofthereturnti
5、mesofsucheventsduetouncertaintiesinthetailsoftheprobabilitydistributionfunction.UsingEVTandGOESX-rayfluxdataitisshownthattheexpected150-yearreturnlevelisapproximatelyanX60flarewhilstaCarrington-likeflareisaoneina100-yearevent.ItisalsoshownthattheEVTres
6、ultsareconsistentwithflaredatafromtheKeplerspacetelescopemission.arXiv:1604.03325vPreprintOctober19th20171IntroductionInthepopularpress,solarflareshavebecomesynonymouswithspaceweathereventseventhoughtheydonotdirectlycausemostofthemajorspaceweathereffec
7、ts[Hapgood,2012].However,themagnitudeofaflareusuallyprovidesanindicationofthetotalamountofenergyinaspaceweatherevent.Flarepeakfluxesareclassifiedbytheletters,A,B,C,MandXwhereeachletterindicatesaflareoneorderofmagnitudelargerthantheonepreceding.AnA1flar
8、ehasapeakX-rayfluxof1×10−8Wm-2(measuredinthe0.1to0.8nmrange)whilstanX1flarehas1×10−4Wm-2.Extremespaceweatherevents(solarsuperstorms)areoftencomparedtotheCarringtoneventof1859[Carrington,1859].TheCarringtoneventisthoughttobethelargestobs
