Abstract
Mariner 10 measurements proved the existence of a large-scale internal magnetic field on Mercury. The observed field amplitude, however, is too weak to be compatible with typical convective planetary dynamos. The Lorentz force based on an extrapolation of Mariner 10 data to the dynamo region is 10−4 times smaller than the Coriolis force. This is at odds with the idea that planetary dynamos are thought to work in the so-called magnetostrophic regime, where Coriolis force and Lorentz force should be of comparable magnitude. Recent convective dynamo simulations reviewed here seem to resolve this caveat. We show that the available convective power indeed suffices to drive a magnetostrophic dynamo even when the heat flow though Mercury’s core–mantle boundary is subadiabatic, as suggested by thermal evolution models. Two possible causes are analyzed that could explain why the observations do not reflect a stronger internal field. First, toroidal magnetic fields can be strong but are confined to the conductive core, and second, the observations do not resolve potentially strong small-scale contributions. We review different dynamo simulations that promote either or both effects by (1) strongly driving convection, (2) assuming a particularly small inner core, or (3) assuming a very large inner core. These models still fall somewhat short of explaining the low amplitude of Mariner 10 observations, but the incorporation of an additional effect helps to reach this goal: The subadiabatic heat flow through Mercury’s core–mantle boundary may cause the outer part of the core to be stably stratified, which would largely exclude convective motions in this region. The magnetic field, which is small scale, strong, and very time dependent in the lower convective part of the core, must diffuse through the stagnant layer. Here, the electromagnetic skin effect filters out the more rapidly varying high-order contributions and mainly leaves behind the weaker and slower varying dipole and quadrupole components (Christensen in Nature 444:1056–1058, 2006). Messenger and BepiColombo data will allow us to discriminate between the various models in terms of the magnetic fields spatial structure, its degree of axisymmetry, and its secular variation.
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References
M.H. Acuña, J.E.P. Connerney, N.F. Ness, R.P. Lin, D. Mitchell, C.W. Carlson, J. McFadden, K.A. Anderson, H. Réme, C. Mazelle, D. Vignes, P. Wasilewski, P. Cloutier, Global distribution of crustal magnetization discovered by the Mars Global Surveyor MAG/ER experiment. Science 284, 790–793 (1999)
O. Aharonson, M.T. Zuber, S. Solomon, Crustal remanence in an internally magnetized non-uniform shell: A possible source for Mercury’s magnetic field? Earth Planet. Sci. Lett. 218, 261–268 (2004)
K.A. Anderson, D.E. Wilhelms, Correlation of lunar farside magnetized regions with ringed impact basins. Earth Planet. Sci. Lett. 46, 107–112 (1979)
J. Arkani-Hamed, Magnetization of Martian lower crust: Revisited. J. Geophys. Res. 112(E11), 5008 (2007)
N. Artemieva, L. Hood, B. Ivanov, Impact demagnetization of the Martian crust: Primaries versus secondaries. Geophys. Res. Lett. 32, L22204 (2005)
J. Aubert, Steady zonal flows in spherical shell dynamos. J. Fluid Mech. 542, 53–67 (2005)
S.I. Braginsky, P.H. Roberts, Equations governing convection in Earth’s core and the geodynamo. Geophys. Astrophys. Fluid Dyn. 79, 1–97 (1995)
D. Breuer et al., Interior evolution of Mercury. Space Sci. Rev. (2007). doi:10.1007/s11214-007-9228-9
D. Breuer, T. Spohn, Early plate tectonics versus single-plate tectonics on Mars: Evidence from magnetic field history and crust evolution. J. Geophys. Res. (Planets) 108, 8–1 (2003)
M. Buske, U.R. Christensen, (2007). Three-dimensional convection models for the thermal evolution of the martian interior (2007, in prep.)
L. Carporzen, S. Gilder, R. Hart, Palaeomagnetism of the Vredefort meteorite crater and implications for craters on Mars. Nature 435, 198–201 (2005)
U. Christensen, J. Wicht, Numerical dynamo simulations, in Core Dynamics, Treatise on Geophysics (Elsevier, 2007)
U. Christensen, P. Olson, G.A. Glatzmaier, Numerical modeling of the geodynamo: A systematic parameter study. Geophys. J. Int. 138, 393–409 (1999)
U.R. Christensen, A deep rooted dynamo for Mercury. Nature 444, 1056–1058 (2006)
U.R. Christensen, J. Aubert, Scaling properties of convection-driven dynamos in rotating spherical shells and applications to planetary magnetic fields. Geophys. J. Int. 166, 97–114 (2006)
U.R. Christensen, A. Tilgner, Power requirement of the geodynamo from ohmic losses in numerical and laboratory dynamos. Nature 429, 169–171 (2004)
U.R. Christensen, J. Aubert, F.H. Busse, P. Cardin, E. Dormy, S. Gibbons, G.A. Glatzmaier, Y. Honkura, C.A. Jones, M. Kono, M. Matsushima, A. Sakuraba, F. Takahashi, A. Tilgner, J. Wicht, K. Zhang, A numerical dynamo benchmark. Phys. Earth Planet. Interiors 128, 25–34 (2001)
J.E.P. Connerney, N.F. Ness, Magnetic field and interior, in Mercury, ed. by F. Vilas, C.R. Chapman, M.S. Matthews (The University of Arizona Press, Tucson, 1988), pp. 494–513
J.E.P. Connerney, M.H. Acuña, N.F. Ness, G. Kletetschka, D.L. Mitchell, R.P. Lin, H. Rme, Tectonic implications of Mars crustal magnetism. Proc. Nat. Acad. Sci. 102, 42 (2005)
V. Conzelmann, Thermische Evolutionsmodelle des Planeten Merkur berechnet unter der Anwendung verschiedener Viskositätsgesetzte. Ph.D. thesis, Westfälische Wilhelms Universität Münster (1999)
M. Fujimoto, W. Baumjohann, K. Kabin, R. Nakamura, J.A. Slavin, N. Terada, L. Zelenyi, Space Sci. Rev. (2007, this issue). doi:10.1007/s11214-007-9245-8
G. Giampieri, A. Balogh, Mercury’s thermoelectric dynamo model resvisisted. Planet. Space Sci. 50, 757–762 (2002)
Glassmeier, K.-H., Grosser, J., Auster, H.-U., Constantinescu, D., Narita, Y., Stellmach, S., Electromagnetic induction effects and dynamo action in the Hermean system. Space Sci. Rev. (2007). doi:10.1007/s11214-007-9244-9
S.A. Hauk, A.J. Dombard, R.J. Phillips, S.C. Solomon, Internal and tectonic evolution of Mercury. Earth Planet. Sci. Lett. 222, 713–728 (2004)
M.H. Heimpel, J.M. Aurnou, F.M. Al-Shamali, N. Gomez Perez, A numerical study of dynamo action as a function of sperical shell geometry. Phys. Earth Planet. Interiors 236, 542–557 (2005)
R. Hollerbach, On the theory of the geodynamo. Phys. Earth Planet. Interiors 98, 163–185 (1996)
R. Hollerbach, C.A. Jones, Influence of the Earth’s inner core on geomagnetic fluctuations and reversals. Nature 365, 541–543 (1993)
L.L. Hood, A. Zakharian, J. Halekas, D.L. Mitchell, R.P. Lin, M. Acuña, A.B. Binder, Initial mapping and interpretation of lunar crustal magnetic anomalies using Lunar Prospector magnetometer data. J. Geophys. Res. 106, 27,825–27,839 (2001)
W. Kuang, J. Bloxham, An Earth-like numerical dynamo model. Nature 389, 371–374 (1997)
C. Kutzner, U.R. Christensen, From stable dipolar to reversing numerical dynamos. Phys. Earth Planet. Interiors 131, 29–45 (2002)
C. Kutzner, U.R. Christensen, Simulated geomagnetic reversals and preferred virtual geomagnetic pole paths. Geophys. J. Int. 157, 1105–1118 (2004)
B. Langlais, M.E. Purucker, M. Mandea, The crustal magnetic field of Mars. J. Geophys. Res. 109 (2004).
V. Lesur, S. Maus, A global lithospheric magnetic field model with reduced noise level in the polar regions. Geophys. Res. Lett. 33 (2006)
J.R. Lister, B.A. Buffett, The strength and efficiency of thermal and compositional convection n the geodynamo. Phys. Earth Planet. Interiors 91, 17–30 (1995)
J.G. Luhmann, The solar wind interaction with Venus. Space Sci. Rev. 44, 241 (1986)
M. Mandea, M. Purucker, Observing, modeling, and interpreting magnetic fields of the solid Earth. Surv. Geophys. 26, 415–459 (2005)
M. Mandea, E. Bellanger, J.-L. Le Mouël, A geomagnetic jerk for the end of 20th century? Earth Planet. Sci. Lett. 183, 369–373 (2000)
J.L. Margot, S.J. Peale, R.F. Jurgens, M.A. Slade, I.V. Holin, Large longitude libration of Mercury reveals a molten core. Science 316, 710–00 (2007)
S. Maus, M. Rother, C. Stolle, W. Mai, S. Choi, H. Lühr, D. Cooke, C. Roth, Third generation of the potsdam magnetic model of the earth (POMME). Geochem. Geophys. Geosyst. 7, 7008 (2006)
N.F. Ness, The magnetic field of Mercury. Phys. Earth Planet. Interiors 20, 209–217 (1979)
N. Olsen, H. Lühr, T.J. Sabaka, M. Mandea, M. Rother, L. Tofner-Clausen, S. Choi, Geophys. J. Int. 166, 67–75 (2006)
P. Olson, U.R. Christensen, Dipole moment scaling for convection-driven planetary dynamos. Earth Planet. Sci. Lett. 250, 561–571 (2006)
P. Olson, U. Christensen, G.A. Glatzmaier, Numerical modeling of the geodynamo: Mechanism of field generation and equilibration. J. Geophys. Res. 104, 10,383–10,404 (1999)
J. Rotvig, C.A. Jones, Rotating convection-driven dynamos at low Ekman number. Phys. Rev. E 66(5), 056308 (2002)
S.K. Runcorn, An acient lunar magnetic dipole field. Nature 253, 701–703 (1975)
G. Schubert, M.N. Ross, D.J. Stevenson, T. Spohn, Mercury’s thermal history and the generation of its magnetic field, in Mercury, ed. by F. Vilas, C.R. Chapman, M.S. Matthews (The University of Arizona Press, Tucson, 1988), pp. 651–666
G. Siscoe, N.F. Ness, C.M. Yeates, Substorms on Mercury? J. Geophys. Res. 80, 4359 (1975)
T. Spohn, M.H. Acuña, D. Breuer, M. Golombek, R. Greeley, A. Halliday, E. Hauber, R. Jaumann, F. Sohl, Geophysical constraints on the evolution of Mars. Space Sci. Rev. 96, 231–262 (2001)
T. Spohn, F. Sohn, K. Wieczerkowski, V. Conzelmann, The interior structure of Mercury: What we know, what we expect from BepiColombo. Planet. Space Sci. 49, 1561–1570 (2001)
S. Stanley, J. Bloxham, W.E. Hutchison, M.T. Zuber, Thin shell dynamo models consistent with Mercury’s weak observed magnetic field. Earth Planet. Sci. Lett. 234, 341–353 (2005)
S. Stellmach, U. Hansen, Cartesian convection driven dynamos at low Ekman number. Phys. Rev. E 70(5), 056312 (2004)
D.J. Stevenson, Mercury’s magnetic field: A thermoelectric dynamo? Earth Planet. Sci. Lett. 82, 114–120 (1987)
D.J. Stevenson, T. Spohn, G. Schubert, Magnetism and thermal evolution of terrestrial planets. Icarus 54, 466–489 (1983)
F. Takahashi, M. Matsushima, Dynamo action in a rotating spherical shell at high Rayleigh numbers. Phys. Fluids 17, 076601 (2005)
F. Takahashi, M. Matsushima, Dipolar and non-dipolar dynamos in a thin shell geometry with implications for the magnetic field of Mercury. Geophys. Res. Lett. 33, L10202 (2006)
F. Takahashi, M. Matsushima, Y. Honkura, Dynamo action and its temporal variation inside the tangent cylinder in MHD dynamo simulations. Phys. Earth Planet. Interiors 140, 53–71 (2003)
R. Tyler, L. Mysak, J. Oberhuber, Electromagnetic fields generated by a three dimensional global ocean circulation. J. Geophys. Res. 102, 5531–5551 (1997)
R. Tyler, A. Maus, H. Lühr, Satellite observations of magnetic fields due to ocean tidal flow. Science 299, 239–241 (2003)
B.P. Weiss, S.S. Kim, J.L. Kirschvink, R.E. Kopp, M. Sankaran, A. Kobayashi, A. Komeili, Ferromagnetic resonance and low-temperature magnetic tests for biogenic magnetite. Earth Planet. Sci. Lett. 224, 73–89 (2004)
J. Wicht, Inner-core conductivity in numerical dynamo simulations. Phys. Earth Planet. Interiors 132, 281–302 (2002)
J. Wicht, Palaeomagnetic interpretation of dynamo simulations. Geophys. J. Int. 162, 371–380 (2005)
J. Wicht, P. Olson, A detailed study of the polarity reversal mechanism in a numerical dynamo model. Geochem. Geophys. Geosyst. 5, 3 (2004)
J.-P. Williams, F. Nimmo, Thermal evolution of the Martian core: Implications for an early dynamo. Geology 32, 97 (2004)
K.-K. Zhang, F.H. Busse, Finite amplitude convection and magnetic field generation in in a rotating spherical shell. Geophys. Astrophys. Fluid Dyn. 44, 33–53 (1988)
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Wicht, J., Mandea, M., Takahashi, F., Christensen, U.R., Matsushima, M., Langlais, B. (2008). The Origin of Mercury’s Internal Magnetic Field. In: Balogh, A., Ksanfomality, L., von Steiger, R. (eds) Mercury. Space Sciences Series of ISSI, vol 26. Springer, New York, NY. https://doi.org/10.1007/978-0-387-77539-5_5
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