Determination of the properties of Mercury's magnetic field by the MESSENGER mission |
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Authors: | Haje Korth Brian J Anderson James A Slavin Sean C Solomon |
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Institution: | a Applied Physics Laboratory, The Johns Hopkins University, 11100 John Hopkins Road, Laurel, MD 20723-6099, USA b NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA c Carnegie Institution of Washington, Department of Terrestrial Magnetism, 5241 Broad Ranch Road, N.W., Washington, DC 20015, USA |
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Abstract: | The MESSENGER mission to Mercury, to be launched in 2004, will provide an opportunity to characterize Mercury's internal magnetic field during an orbital phase lasting one Earth year. To test the ability to determine the planetary dipole and higher-order moments from measurements by the spacecraft's fluxgate magnetometer, we simulate the observations along the spacecraft trajectory and recover the internal field characteristics from the simulated observations. The magnetic field inside Mercury's magnetosphere is assumed to consist of an intrinsic multipole component and an external contribution due to magnetospheric current systems described by a modified Tsyganenko 96 model. Under the axis-centered-dipole approximation without correction for the external field the moment strength is overestimated by ∼4% for a simulated dipole moment of , and the error depends strongly on the magnitude of the simulated moment, rising as the moment decreases. Correcting for the external field contributions can reduce the error in the dipole term to a lower limit of ∼1-2% without a solar wind monitor. Dipole and quadrupole terms, although highly correlated, are then distinguishable at the level equivalent to an error in the position of an offset dipole of a few tens of kilometers. Knowledge of the external magnetic field is therefore the primary limiting factor in extracting reliable knowledge of the structure of Mercury's magnetic field from the MESSENGER observations. |
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Keywords: | Mercury MESSENGER mission Magnetic field Multipole inversion |
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