title: The global magnetic field of Mercury from MESSENGER orbital observations.
abstract: Magnetometer data acquired by the MESSENGER spacecraft in orbit about Mercury permit the separation of internal and external magnetic field contributions. The global planetary field is represented as a southward-directed, spin-aligned, offset dipole centered on the spin axis. Positions where the cylindrical radial magnetic field component vanishes were used to map the magnetic equator and reveal an offset of 484 ± 11 kilometers northward of the geographic equator. The magnetic axis is tilted by less than 3° from the rotation axis. A magnetopause and tail-current model was defined by using 332 magnetopause crossing locations. Residuals of the net external and offset-dipole fields from observations north of 30°N yield a best-fit planetary moment of 195 ± 10 nanotesla-R(M)(3), where R(M) is Mercury's mean radius.
authors.affiliation: The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA. brian.anderson@jhuapl.edu
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Anderson
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Johnson
authors.forename: Haje
authors.initials: H
authors.lastname: Korth
authors.forename: Michael E
authors.initials: ME
authors.lastname: Purucker
authors.forename: Reka M
authors.initials: RM
authors.lastname: Winslow
authors.forename: James A
authors.initials: JA
authors.lastname: Slavin
authors.forename: Sean C
authors.initials: SC
authors.lastname: Solomon
authors.forename: Ralph L
authors.initials: RL
authors.lastname: McNutt
authors.forename: Jim M
authors.initials: JM
authors.lastname: Raines
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Zurbuchen