10:45 AM - 12:15 PM
[PPS07-P16] Estimated depth to the Hermean dynamo region using Mercury's magnetic energy spectrum
Keywords:Mercury, Mauersberger spectrum, Lowes radius, planetary dynamo
MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) was the first spacecraft to enter Mercury's orbit. Based on these data, the Gaussian coefficient of Mercury's intrinsic magnetic field was also estimated (Anderson et al., 2012). The intrinsic magnetic field strength of Mercury is smaller than that of its large metallic core, suggesting a stratified inner structure above the outer core (Christensen, 2006), and dynamo simulations based on this structure have recently reproduced the northward offset of Mercury's surface magnetic field (Takahashi et al.)
When the Mauersberger spectrum, which is the mean energy density spectrum of the potential magnetic field, is obtained from the Gauss coefficient, the Lowes radius estimated from the slope corresponds to the radius of the current sphere in the planetary interior, or the radius of the dynamo region. While the Earth's Lowes radius is close to the core-mantle boundary radius, the Lowes radius estimated from the Gaussian coefficient of Mercury's intrinsic magnetic field is considerably smaller than the Mercury core-mantle boundary estimated from the magnetic field induced by Mercury's core in response to changes in the external magnetic field (Katsura et al., 2020) and many geodetic studies.
For Jupiter, the radial dependence of its intrinsic magnetic field has been calculated from dynamo simulations, and an argument has been made that the Lowes radius gives a lower limit on the dynamo radius by comparing the slope of the Mauersberger spectrum with the energy spectrum obtained (Tsang and Jones, 2019).
In this study, we perform dynamo simulations using a model with a stratified upper outer core that reproduces Mercury's intrinsic magnetic field to obtain the mean magnetic field energy density spectrum of the intrinsic magnetic field in Mercury's interior. The dynamo radius estimated from the comparison between the spectrum and the Mauersberger spectrum on Mercury's surface is compared/validated with the existing structure of Mercury's interior.
When the Mauersberger spectrum, which is the mean energy density spectrum of the potential magnetic field, is obtained from the Gauss coefficient, the Lowes radius estimated from the slope corresponds to the radius of the current sphere in the planetary interior, or the radius of the dynamo region. While the Earth's Lowes radius is close to the core-mantle boundary radius, the Lowes radius estimated from the Gaussian coefficient of Mercury's intrinsic magnetic field is considerably smaller than the Mercury core-mantle boundary estimated from the magnetic field induced by Mercury's core in response to changes in the external magnetic field (Katsura et al., 2020) and many geodetic studies.
For Jupiter, the radial dependence of its intrinsic magnetic field has been calculated from dynamo simulations, and an argument has been made that the Lowes radius gives a lower limit on the dynamo radius by comparing the slope of the Mauersberger spectrum with the energy spectrum obtained (Tsang and Jones, 2019).
In this study, we perform dynamo simulations using a model with a stratified upper outer core that reproduces Mercury's intrinsic magnetic field to obtain the mean magnetic field energy density spectrum of the intrinsic magnetic field in Mercury's interior. The dynamo radius estimated from the comparison between the spectrum and the Mauersberger spectrum on Mercury's surface is compared/validated with the existing structure of Mercury's interior.