Synchrony between dipole and quadrupole during magnetic field reversals and excursions

Capa

Citar

Texto integral

Acesso aberto Acesso aberto
Acesso é fechado Acesso está concedido
Acesso é fechado Acesso é pago ou somente para assinantes

Resumo

In contrast to reversals, excursions of the geomagnetic field can occur at lower convection intensities in the Earth’s core. Since in such geodynamo regimes the behavior of the magnetic field is still quasi regular, a reduction of the dipole field during an excursion may indicate a global failure of the dynamo process. As a consequence, it is possible that during the excursion, not only the dipole component, but also the higher harmonics of the field decrease. This hypothesis is tested in a three-dimensional (3D) dynamo model.

Texto integral

Acesso é fechado

Sobre autores

M. Reshetnyak

Schmidt Institute of Physics of the Earth, Russian Academy of Sciences; Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences

Autor responsável pela correspondência
Email: m.reshetnyak@gmail.com
Rússia, Moscow; Moscow

Bibliografia

  1. Решетняк М.Ю. Инверсии геомагнитного поля: ограничение на интенсивность конвекции в ядре Земли? // Геомагнетизм и Аэрономия. 2021. Т. 61. № 2. C. 267–272.
  2. Решетняк М.Ю. Адаптация модели среднего поля в геодинамо // Физика Земли. 2017. № 4. C. 93–99.
  3. Краузе Ф., Рэдлер К.-Х. Магнитная гидродинамика средних полей и теория динамо. М.: Мир. 1984.
  4. Christensen U.R., Tilgner A. Power requirement of the geodynamo from ohmic losses in numerical and laboratory dynamos // Nature. 2004. V. 429. № 6988. P. 169.
  5. Christensen U., Aubert J. Scaling properties of convection-driven dynamos in rotating spherical shells and application to planetary magnetic fields // Geophys. J. Int. 2006. V. 166. P. 97–114.
  6. Hollerbach R., Jones C.A. Influence of the Earth’s inner core on reversals // Nature. 1993. V. 365. P. 541–546.
  7. Glatzmaier G.A. Introduction to modeling convection in planets and stars: Magnetic field, density stratification, rotation. Princeton University Press. 2013.
  8. Gubbins D. The distinction between geomagnetic excursions and reversals // Geophys. J. Int. 1999. V. 137. № 1. P. F1–F3.
  9. Hulot G., Mouël J.Le. A statistical approach to the earth’s main magnetic field // Phys. Earth Planet. Int. 1994. V. 82. № 3-4. P. 167–183.
  10. Ogg J. Geomagnetic polarity time scale. Elsevier. 2020.
  11. Valet J.-P. Time variations in geomagnetic intensity // Rev. Geophys. 2003. V. 41. № 1. P. 4.
  12. Wicht J. Inner-core conductivity in numerical dynamo simulations // Phys. Earth Planet. Int. 2002. V. 132. № 4. P. 281–302.
  13. Zhang K., Gubbins D. Is the geodynamo process intrinsically unstable? // Geophys. J. Int. 2000. V. 140. № 1. P. F1–F4.

Arquivos suplementares

Arquivos suplementares
Ação
1. JATS XML
2. Fig. 1. Dependence on time t of the angle of deviation of the axial dipole from the geographic axis (a), the amplitude of the axial dipole (b), kinetic Ek (c) and magnetic Em (d) energies, and the axisymmetric quadrupole (e) for Ra = 4 10– 5. The most striking excursions are marked with numbers.

Baixar (594KB)
3. Fig. 2. Dependence on time t of the angle of deviation of the axial dipole from the geographic axis (a), the amplitude of the axial dipole (b), kinetic Ek (c) and magnetic Em (d) energies, and the axisymmetric quadrupole (e) for Ra = 5 10- 5. The numbers indicate the most striking inversions.

Baixar (627KB)
4. Fig. 3. Dependence on time t of the axial dipole (a), (c), (e) and quadrupole (b), (d), (f) during inversions (1, 2, 3) in Fig. 2 respectively on an enlarged scale.

Baixar (368KB)

Declaração de direitos autorais © Russian Academy of Sciences, 2024