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16 - Structure and Configuration of Mercury’s Magnetosphere
- Edited by Sean C. Solomon, Larry R. Nittler, Carnegie Institution of Washington, Washington DC, Brian J. Anderson
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- Book:
- Mercury
- Published online:
- 10 December 2018
- Print publication:
- 20 December 2018, pp 430-460
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Summary
Mercury is the only terrestrial planet other than Earth that possesses a global magnetic field, and the unique solar wind environment of the inner heliosphere has profound consequences for both the structure and dynamics of its magnetosphere. The first in situ observations of Mercury and its space environment made four decades ago by the Mariner 10 spacecraft revealed a magnetic field that is sufficiently strong to stand off the solar wind and form a magnetosphere. Many new insights into Mercury’s magnetosphere were enabled by data returned by the MESSENGER spacecraft. The extensive magnetic field and particle observations allowed detailed characterization of the magnetospheric structure and configuration. MESSENGER magnetic field observations definitively determined the orientation, moment, and location of the internal planetary magnetic dipole field. Furthermore, these observations established the configuration of the magnetopause, bow shock, and magnetospheric current systems. Plasma observations revealed the distribution and composition of plasma in the magnetosphere. We review the geometry and dominant physical processes of Mercury’s unique magnetosphere inferred from MESSENGER data, including the solar wind environment, the shape and location of magnetospheric boundaries, and the fundamental regions and configuration of the magnetosphere and transport and heating of plasma therein.
5 - Mercury’s Internal Magnetic Field
- Edited by Sean C. Solomon, Larry R. Nittler, Carnegie Institution of Washington, Washington DC, Brian J. Anderson
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- Book:
- Mercury
- Published online:
- 10 December 2018
- Print publication:
- 20 December 2018, pp 114-143
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- Chapter
- Export citation
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Summary
The MESSENGER mission provided a wealth of discoveries regarding Mercury’s present and past magnetic field and completed the first-order characterization of the magnetic fields of the solar system’s inner planets. MESSENGER demonstrated that Mercury is the only inner planet other than Earth to possess a global magnetic field generated by fluid motions in its liquid iron core. The field possesses some similarities to that of Earth, particularly its dipolar nature, but it is more than a factor of 100 weaker at the surface and unlike Earth’s field is highly asymmetric about the geographic equator. This structure constrains the dynamo process that generates the field and in turn the compositional and thermal structure of Mercury’s interior. Measurements made by MESSENGER less than 100 km above the planetary surface revealed signatures of crustal magnetization, at least some of which were acquired in a very ancient global magnetic field. Electric currents flow in the planet’s interior as a result of the dynamic interactions of the global magnetic field with the solar wind. These currents provide information on the radius of Mercury’s electrically conductive core, as well as the conductivity structure of the crust and mantle, which in turn reflects interior composition and temperature.