LabellingJupiterMagneticFieldLines

FranBagenal &DrakeRanquistUniversityofColorado,Boulder

October14th 2016MWGtelecon

Whattocallthis?

MagneticL-Shell

InternalField– VIP4Connerney

Radial Current

Azimuthal Current

ExternalCurrents

𝜵xBobserved➔J⊥

∇•J=0➔J||

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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!