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LabellingJupiterMagneticFieldLines
FranBagenal &DrakeRanquistUniversityofColorado,Boulder
October14th 2016MWGtelecon
Whattocallthis?
MagneticL-Shell
InternalField– VIP4Connerney
Radial Current
Azimuthal Current
ExternalCurrents
𝜵xBobserved➔J⊥
∇•J=0➔J||
“
”
JackConnerney’s slide– MarchJunomeetingConnerney,Acuna,Ness1981– Voyager
JupitermagneticfieldmodelofKhurana basedonMAGdatafrom33Galileoorbits–VIP4internal+variablecurrentsheet+
magnetopause currentsSideView LookingDown
TheWigglePlot
JunoTrajectory– inTiltedDipoleCoordinates
Sincethemagnetic field is3-Dandvaryingwithtime asJunomovesalongthetrajectory,weshowhere"typical"field lines thatshowthesameofmagneticfield lines thatcrosstheequatoratthese distancesof10,20,30,40,and50RJ– usingtheVIP4+Khurana magnetic field.
MagneticFieldLine:Farthestpoint=MagneticEquator&Brchangessign
ORBIT3– inTiltedDipoleCoordinates
*
TimeAlongJunoTrajectory
Farthestpointalongthefieldline
Whattocallthisdistance?Rmeq?L-Shell=DipoleM-Shell- ???J-Shell- ???V-shell- ???BarryusesVIP-L
JunoOrbitVIP4
VIP4+Khurana
VIP4+CAN
VIP4only??
Nov15(DOY320)17:00R~20RJ
Nov17(322)1:00R~10RJPJ4
Nov16(DOY321)17:00
Pros ConsVIP4 Simplest Doesnotwork
> “L~10”
VIP4+CAN
SimpleAximuthally symmetricQuickcalculation
Only validwhenRmeq<30
VIP4+Khurana
BasedonmoredataVarieswithlongitudeVarieswithlocaltimeVarieswithabsolutetime
NotsimpleVarieswithlongitudeVarieswithlocaltimeNeedsabsolutetimeComputationallyheavy
Isitnecessarily moreaccurate?
Bill’sProposal:
• UseDipolebasedonVIP4– callthisDipoleL-shell– Buyer-beware:thishasincreasingerror>10
• UseVIP4– callthisVIP4-L– Buyer-beware:thishasincreasingerror>10
• UseVIP4+CAN– callthisRmeq– Buyer-beware:thishasincreasingerror>30
BOTTOMLINE=LABEL,LABEL,LABEL!