Russian Journal of Earth Sciences Russian Journal of Earth Sciences Russian Journal of Earth Sciences 1681-1208 104020 10.2205/2026es001104 suvkcm ОРИГИНАЛЬНЫЕ СТАТЬИ ORIGINAL ARTICLES ОРИГИНАЛЬНЫЕ СТАТЬИ Superdipole Geomagnetic Field in the Past Superdipole Geomagnetic Field in the Past https://orcid.org/0000-0002-4909-6336 Решетняк Максим Юрьевич Reshetnyak Maxim Yurievich m.reshetnyak@gmail.com

доктор физико-математических наук;

doctor of physical and mathematical sciences;

 Институт физики Земли им. О.Ю. Шмидта РАН Москва Россия Schmidt Institute of Physics of the Earth Moscow Russian Federation 16 03 2026 16 03 2026 26 1 ES1008 09 09 2025 27 02 2026 https://rjes.ru/en/nauka/article/104020/view

According to the model of the Earth’s cooling, before the solid core origin, there was a sub-adiabatic layer at the core-mantle boundary several hundred kilometers thick. In this layer magnetic field generation was suppressed. Removing the field generation region from the Earth’s surface led to an effective weakening of the small-scale component of the magnetic field. After the solid core appeared, convection extended throughout the whole bulk of the core with the possible exception of the F-layer at the core-mantle boundary, which is no more than 100 km thick. As a result the non-dipole counterpart of the magnetic field should be stronger at the Earth’s surface. The decrease of the ratio of the dipole to non-dipole field with the origin of the solid core was an order of magnitude or more.

According to the model of the Earth’s cooling, before the solid core origin, there was a sub-adiabatic layer at the core-mantle boundary several hundred kilometers thick. In this layer magnetic field generation was suppressed. Removing the field generation region from the Earth’s surface led to an effective weakening of the small-scale component of the magnetic field. After the solid core appeared, convection extended throughout the whole bulk of the core with the possible exception of the F-layer at the core-mantle boundary, which is no more than 100 km thick. As a result the non-dipole counterpart of the magnetic field should be stronger at the Earth’s surface. The decrease of the ratio of the dipole to non-dipole field with the origin of the solid core was an order of magnitude or more.

 geodynamo core-mantle boundary Earth’s cooling inner core geodynamo core-mantle boundary Earth’s cooling inner core The work was performed within the framework of a State Assignment of the Institute of Physics of the Earth of Russian Academy of Sciences. The work was performed within the framework of a State Assignment of the Institute of Physics of the Earth of Russian Academy of Sciences.

Abe Y. Physical state of the very early Earth // Lithos. — 1993. — Vol. 30, no. 3/4. — P. 223–235. — https://doi.org/10.1016/0024-4937(93)90037-d. Abe Y. Physical state of the very early Earth // Lithos. — 1993. — Vol. 30, no. 3/4. — P. 223–235. — https://doi.org/10.1016/0024-4937(93)90037-d. Aubert J. State and evolution of the geodynamo from numerical models reaching the physical conditions of Earth’s core // Geophys. J. Int. — 2023. — Vol. 235, no. 1. — P. 468–487. — https://doi.org/10.1093/gji/ggad229. Aubert J. State and evolution of the geodynamo from numerical models reaching the physical conditions of Earth’s core // Geophys. J. Int. — 2023. — Vol. 235, no. 1. — P. 468–487. — https://doi.org/10.1093/gji/ggad229. Braginsky S.I. Structure of the F layer and reasons for convection in the Earth’s core // Dokl. Akad. Nauk. SSSR Engl. Trans. — 1963. — Vol. 149. — P. 1311–1314. Braginsky S.I. Structure of the F layer and reasons for convection in the Earth’s core // Dokl. Akad. Nauk. SSSR Engl. Trans. — 1963. — Vol. 149. — P. 1311–1314. Christensen U. Geodynamo models with a stable layer and heterogeneous heat flow at the top of the core // Geophys. J. Int. — 2018. — Vol. 215, no. 2. — P. 1338–1351. — https://doi.org/10.1093/gji/ggy352. Christensen U. Geodynamo models with a stable layer and heterogeneous heat flow at the top of the core // Geophys. J. Int. — 2018. — Vol. 215, no. 2. — P. 1338–1351. — https://doi.org/10.1093/gji/ggy352. Christensen U. and Aubert J. Scaling properties of convection-driven dynamos in rotating spherical shells and application to planetary magnetic fields // Geophys. J. Int. — 2006. — Vol. 166. — P. 97–114. — https://doi.org/10.1111/j.1365-246X.2006.03009.x. Christensen U. and Aubert J. Scaling properties of convection-driven dynamos in rotating spherical shells and application to planetary magnetic fields // Geophys. J. Int. — 2006. — Vol. 166. — P. 97–114. — https://doi.org/10.1111/j.1365-246X.2006.03009.x. Christensen U., Aubert J. and Hulot G. Conditions for Earth-like geodynamo models // Earth Planet. Sci. Lett. — 2010. — Vol. 296, no. 3/4. — P. 487–496. — https://doi.org/10.1016/j.epsl.2010.06.009. Christensen U., Aubert J. and Hulot G. Conditions for Earth-like geodynamo models // Earth Planet. Sci. Lett. — 2010. — Vol. 296, no. 3/4. — P. 487–496. — https://doi.org/10.1016/j.epsl.2010.06.009. Gastine T., Aubert J. and Fournier A. Dynamo-based limit to the extent of a stable layer atop Earth’s core // Geophys. J. Int. — 2020. — Vol. 222, no. 2. — P. 1433–1448. — https://doi.org/10.1093/gji/ggaa250. Gastine T., Aubert J. and Fournier A. Dynamo-based limit to the extent of a stable layer atop Earth’s core // Geophys. J. Int. — 2020. — Vol. 222, no. 2. — P. 1433–1448. — https://doi.org/10.1093/gji/ggaa250. Gubbins D., Alfè D., Davies C.J., et al. On core convection and the geodynamo: Effects of high electrical and thermal conductivity // Phys. Earth Planet. Int. — 2015. — Vol. 247. — P. 56–64. — https://doi.org/10.1016/j.pepi.2015.04.002. Gubbins D., Alfè D., Davies C.J., et al. On core convection and the geodynamo: Effects of high electrical and thermal conductivity // Phys. Earth Planet. Int. — 2015. — Vol. 247. — P. 56–64. — https://doi.org/10.1016/j.pepi.2015.04.002. Gubbins D. and Davies C.J. The stratified layer at the core–mantle boundary caused by barodiffusion of oxygen, sulphur and silicon // Phys. Earth Planet. Int. — 2013. — Vol. 215. — P. 21–28. — https://doi.org/10.1016/j.pepi.2012.11.001. Gubbins D. and Davies C.J. The stratified layer at the core–mantle boundary caused by barodiffusion of oxygen, sulphur and silicon // Phys. Earth Planet. Int. — 2013. — Vol. 215. — P. 21–28. — https://doi.org/10.1016/j.pepi.2012.11.001. Gubbins D., Thomson C.J. and Whaler K.A. Stable regions in the Earth’s liquid core // Geophys. J. Roy. Astr. Soc. — 1982. — Vol. 68, no. 1. — P. 241–251. — https://doi.org/10.1111/j.1365-246X.1982.tb06972.x. Gubbins D., Thomson C.J. and Whaler K.A. Stable regions in the Earth’s liquid core // Geophys. J. Roy. Astr. Soc. — 1982. — Vol. 68, no. 1. — P. 241–251. — https://doi.org/10.1111/j.1365-246X.1982.tb06972.x. Labrosse S., Poirier J.-P. and Le Mouël J.-L. On cooling of the Earth’s core // Phys. Earth Planet. Int. — 1997. — Vol. 99, no. 1. — P. 1–17. — https://doi.org/10.1016/S0031-9201(96)03207-4. Labrosse S., Poirier J.-P. and Le Mouël J.-L. On cooling of the Earth’s core // Phys. Earth Planet. Int. — 1997. — Vol. 99, no. 1. — P. 1–17. — https://doi.org/10.1016/S0031-9201(96)03207-4. Labrosse S., Poirier J.-P. and Le Mouël J.-L. The age of the inner core // Earth Planet. Sci. Lett. — 2001. — Vol. 190, no. 3/4. — P. 111–123. — https://doi.org/10.1016/S0012-821X(01)00387-9. Labrosse S., Poirier J.-P. and Le Mouël J.-L. The age of the inner core // Earth Planet. Sci. Lett. — 2001. — Vol. 190, no. 3/4. — P. 111–123. — https://doi.org/10.1016/S0012-821X(01)00387-9. Lowes F.J. Spatial power spectrum of the main geomagnetic field // Geophys. J. R. Astr. Soc. — 1974. — Vol. 36. — P. 717–725. — https://doi.org/10.1111/j.1365-246x.1974.tb00622.x. Lowes F.J. Spatial power spectrum of the main geomagnetic field // Geophys. J. R. Astr. Soc. — 1974. — Vol. 36. — P. 717–725. — https://doi.org/10.1111/j.1365-246x.1974.tb00622.x. Nichols C.I.O., Weiss B.P., Eyster A., et al. Eoarchean records of the geomagnetic field preserved in the Isua Supracrustal Belt, southern west Greenland // J. Geophys. Res. Solid Earth. — 2024. — Vol. 129, no. 4. — e2023JB027706. — https://doi.org/10.1029/2023JB027706. Nichols C.I.O., Weiss B.P., Eyster A., et al. Eoarchean records of the geomagnetic field preserved in the Isua Supracrustal Belt, southern west Greenland // J. Geophys. Res. Solid Earth. — 2024. — Vol. 129, no. 4. — e2023JB027706. — https://doi.org/10.1029/2023JB027706. Olson P. The new core paradox // Science. — 2013. — Vol. 342, no. 6157. — P. 431–432. — https://doi.org/10.1126/science.1243477. Olson P. The new core paradox // Science. — 2013. — Vol. 342, no. 6157. — P. 431–432. — https://doi.org/10.1126/science.1243477. Reshetnyak M.Yu. Evolution of the inner core of the Earth: consequences for geodynamo // Magnetohydrodynamics. — 2019. — Vol. 55, no. 1/2. — P. 175–183. Reshetnyak M.Yu. Evolution of the inner core of the Earth: consequences for geodynamo // Magnetohydrodynamics. — 2019. — Vol. 55, no. 1/2. — P. 175–183. Reshetnyak M.Yu. Mantle cooling regulation and ancient geomagnetic field // Russ. J. Earth Sci. — 2022. — Vol. 22. — ES2006. — https://doi.org/10.2205/2022ES000797. Reshetnyak M.Yu. Mantle cooling regulation and ancient geomagnetic field // Russ. J. Earth Sci. — 2022. — Vol. 22. — ES2006. — https://doi.org/10.2205/2022ES000797. Roberts P.-H., Jones C.A. and Calderwood A.R. Energy fluxes and ohmic dissipation in the Earth’s core // Earth’s core and lower mantle / ed. by C.A. Jones, A.M. Soward and K. Zhang. — Taylor, Francis, 2003. — P. 100–129. — https://doi.org/10.1201/9780203207611.CH5. Roberts P.-H., Jones C.A. and Calderwood A.R. Energy fluxes and ohmic dissipation in the Earth’s core // Earth’s core and lower mantle / ed. by C.A. Jones, A.M. Soward and K. Zhang. — Taylor, Francis, 2003. — P. 100–129. — https://doi.org/10.1201/9780203207611.CH5. Rogister Y. and Valette B. Influence of liquid core dynamics on rotation modes // Geophys. J. Int. — 2009. — Vol. 176. — P. 368–388. — https://doi.org/10.1111/j.1365-246X.2008.03996.x. Rogister Y. and Valette B. Influence of liquid core dynamics on rotation modes // Geophys. J. Int. — 2009. — Vol. 176. — P. 368–388. — https://doi.org/10.1111/j.1365-246X.2008.03996.x. Smirnov A.V., Tarduno J.A., Kulakov E.V., et al. Palaeointensity, core thermal conductivity and the unknown age of the inner core // Geophys. J. Int. — 2016. — Vol. 205, no. 2. — P. 1190–1195. — https://doi.org/10.1093/gji/ggw080. Smirnov A.V., Tarduno J.A., Kulakov E.V., et al. Palaeointensity, core thermal conductivity and the unknown age of the inner core // Geophys. J. Int. — 2016. — Vol. 205, no. 2. — P. 1190–1195. — https://doi.org/10.1093/gji/ggw080. Takehiro S. and Lister J.R. Penetration of columnar convection into an outer stably stratified layer in rapidly rotating spherical fluid shells // Earth Planet. Sci. Lett. — 2001. — Vol. 187, no. 3/4. — P. 357–366. — https://doi.org/10.1016/S0012-821X(01)00283-7. Takehiro S. and Lister J.R. Penetration of columnar convection into an outer stably stratified layer in rapidly rotating spherical fluid shells // Earth Planet. Sci. Lett. — 2001. — Vol. 187, no. 3/4. — P. 357–366. — https://doi.org/10.1016/S0012-821X(01)00283-7.