Electrodynamiccouplinginthesolarwind-magnetosphere-ionospheresystem

ThispaperpresentsabriefsummaryofourrecentworkbasedonglobalMHDsimulationsoftheSolarwind-Magnetosphere-Ionosphere(SMI)systemwithemphasisontheelectrodynamiccouplinginthesystem.Themainconclusionsobtainedaresummarizedasfollows.(1)AsamaindynamooftheSMIsystem,thebowshockcontributestobothregion1Field-AlignedCurrent(FAC)andcross-tailcurrent.UnderstronginterplanetarydrivingconditionsandmoderateAlfvenMachnumbers,thebowshock'scontributionmayexceedmorethanfiftypercentofthetotalofeitherregion1orcross-tailcurrents.(2)Intermsofmorethan100simulationrunswithduesouthwardInterplanetaryMagneticField(IMF),wehavefoundacombinedparameterf=EswPswMA-1/2(Esw,Psw,andMAarethesolarwindelectricfield,rampressure,andAlfvenMachnumber,respectively):boththeionospherictranspolarpotentialandthemagnetopausereconnectionvoltagevarylinearlywithfforsmallf,butsaturateforlargef.(3)Thereconnectionvoltageisapproximatelyfittedbysin3/2θIMF/2,whereθIMFistheIMFclockangle.Theionospherictranspolarpotential,thevoltagealongthepolarcapboundary,andtheelectricfieldsalongthemerginglinehoweverdefinedtheymaybe,responddifferentlytoθIMF,soitisnotjustifiedtotakethemassubstitutesforthereconnectionvoltage.