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| Titel |
A New Hermean Magnetic Field Model using a Modified Equivalent Source Dipole Method |
| VerfasserIn |
Joana S. Oliveira, Benoit Langlais, M. Alexandra Pais, Hagay Amit, Erwan Thébault |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250149170
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| Publikation (Nr.) |
 EGU/EGU2017-13496.pdf |
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| Zusammenfassung |
| Mercury is the only terrestrial planet, besides the Earth, that has a core dynamo which
generates a global magnetic field. MESSENGER orbited Mercury from 2011 to 2015 and
provided magnetic measurements which convey crucial information on the magnetic field
environment of the planet. We use a local method based on Equivalent Source Dipole
approach to model the internal field of Mercury. The method is especially well suited when
measurements cover a limited fraction of the planet’s surface. Dipoles are placed deep into
the planet. Note that with this modeling scheme, we do not attempt to explicitly model the
external field. As the planet is in spin-orbit resonance completing three sidereal days in
two years, it takes three sidereal days (one solar day) for the Sun to cover all local
longitudes. We therefore consider successive periods of one solar day. A dominantly
axisymmetric field is found for each solar-day model showing a significant temporal
variability. This could be due to some large-scale external field that appears as
internal with respect to the spacecraft orbit. The changing altitude and latitude
coverage of each model may also be invoked for this variability. We finally compute
a 8-solar-day model, including all solar days during the MESSENGER mission,
to describe the Hermean magnetic field. Maps of the field computed at 200 km
altitude show a magnetic equator at 16∘N latitude, and confirm the large-scale and
close-to-axisymmetry structure of the internal magnetic field of Mercury. Our model is also
in agreement with the magnetic equator crossings detected before. However, our
magnetic equator latitude varies with the altitude to the planet. This is indicative that
the dipole-offset hypothesis is over-simplified, and that dynamo modelers have
to consider alternative models when attempting to model the Hermean dynamo. |
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