title: The structure of Mercury's magnetic field from MESSENGER's first flyby.
abstract: During its first flyby of Mercury, the MESSENGER spacecraft measured the planet's near-equatorial magnetic field. The field strength is consistent to within an estimated uncertainty of 10% with that observed near the equator by Mariner 10. Centered dipole solutions yield a southward planetary moment of 230 to 290 nanotesla RM3 (where RM is Mercury's mean radius) tilted between 5 degrees and 12 degrees from the rotation axis. Multipole solutions yield non-dipolar contributions of 22% to 52% of the dipole field magnitude. Magnetopause and tail currents account for part of the high-order field, and plasma pressure effects may explain the remainder, so that a pure centered dipole cannot be ruled out.
authors.affiliation: Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, USA. brian.anderson@jhuapl.edu
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Anderson
authors.forename: Mario H
authors.initials: MH
authors.lastname: Acuña
authors.forename: Haje
authors.initials: H
authors.lastname: Korth
authors.forename: Michael E
authors.initials: ME
authors.lastname: Purucker
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Johnson
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