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Based on data obtained from Wilcox Solar Observatiry the solar polar magnetic fields reversals in cycles 21\,--\,25 were considered. The results indicate that the polarity reversal occurs at the maximum of sunspot activity of each cycle,…

Solar and Stellar Astrophysics · Physics 2025-11-03 Irina A. Bilenko

Ground-state fluctuations reduce the zero-temperature magnetic moments of the spins in a quantum antiferromagnet. In the neighborhood of surfaces, interfaces, and other defects which break translational symmetry, these fluctuations are not…

Other Condensed Matter · Physics 2007-05-23 G. J. Mata , E. Pestana , M. Kiwi , H. Dreysse

We argue that global magnetic field reversals similar to those observed in the Milky Way occur quite frequently in mean-field galactic dynamo models that have relatively strong, random, seed magnetic fields that are localized in discrete…

Astrophysics of Galaxies · Physics 2015-06-11 David Moss , Dmitri Sokoloff

The dynamo effect is the most popular candidate to explain the non-primordial magnetic fields of astrophysical objects. Although many systematic studies of parameters have already been made to determine the different dynamical regimes…

Fluid Dynamics · Physics 2020-07-14 Mélissa D. Menu , Ludovic Petitdemange , Sébastien Galtier

A geodynamo-model based on an \alpha-effect which has been computed under conditions suitable for the geodynamo is constructed. For a highly restricted class of radial \alpha-profiles the linear \alpha2-model exhibits oscillating solutions…

Astrophysics · Physics 2009-11-13 A. Giesecke , G. Rudiger , D. Elstner

Convection in the liquid outer core of the Earth is driven by thermal and chemical perturbations. The main purpose of this study is to examine the impact of double-diffusive convection on magnetic field generation by means of 3D global…

Geophysics · Physics 2021-05-12 Théo Tassin , Thomas Gastine , Alexandre Fournier

This paper presents an analysis on the distribution of periods between consecutive reversals of the Earth's magnetic field. The analysis includes the randomness of polarities, whether the data corresponding to different periods belong to a…

Geophysics · Physics 2007-05-23 Cosme F. Ponte-Neto , Andres R. R. Papa

We investigate the nature of the dynamo bifurcation in a configuration applicable to the Earth's liquid outer core. Numerical studies on the stability domain of dipolar magnetic fields found a dichotomy between non-reversing…

Geophysics · Physics 2018-03-14 Ludovic Petitdemange

One of the most remarkable features of the geodynamo is the irregular occurrence of magnetic field reversals. Starting with the operator theoretical treatment of a non-selfadjoint dynamo operator, we elaborate a dynamical picture of those…

Mathematical Physics · Physics 2018-05-02 Frank Stefani , Christiane Tretter

The magnetopause marks the outer edge of the Earth's magnetosphere and a distinct boundary between solar wind and magnetospheric plasma populations. In this letter, we use global magnetohydrodynamic simulations to examine the response of…

The possibility to detect circumbinary planets and to study stellar magnetic fields through eclipsing time variations (ETVs) in binary stars has sparked an increase of interest in this area of research. We revisit the connection between…

Solar and Stellar Astrophysics · Physics 2022-07-20 Felipe H. Navarrete , Petri J. Käpylä , Dominik R. G. Schleicher , Carolina A. Ortiz , Robi Banerjee

We consider one-dimensional long-range spin models (usually called Dyson models), consisting of Ising ferromagnets with slowly decaying long-range pair potentials of the form $\frac{1}{|i-j|^{\alpha}}$ mainly focusing on the range of slow…

Mathematical Physics · Physics 2017-02-10 R. Bissacot , E. O. Endo , A. C. D. van Enter , B. Kimura , A. Le Ny , W. M. Ruszel

The asymmetric time dependence and various statistical properties of polarity reversals of the Earth's magnetic field are utilized to infer some of the most essential parameters of the geodynamo, among them the effective (turbulent)…

Geophysics · Physics 2009-05-15 Michael Fischer , Gunter Gerbeth , Andre Giesecke , Frank Stefani

We show that a slowly decaying current pulse can lead to nearly deterministic precessional switching in the presence of noise. We consider a biaxial macrospin, with an easy axis in the plane and a hard axis out-of-the plane, typical of thin…

Mesoscale and Nanoscale Physics · Physics 2016-05-18 Daniele Pinna , Colm Ryan , Thomas Ohki , Andrew D. Kent

We present the first statistical study of magnetic structures and associated energy dissipation observed during a single period of turbulent magnetic reconnection, by using the \textit{in-situ} measurements of the Magnetospheric Multiscale…

Space Physics · Physics 2020-10-28 K. Bergstedt , H. Ji , J. Jara-Almonte , J. Yoo , R. E. Ergun , L. -J. Chen

Solar magnetic fields comprise an 11-year activity cycle, represented by the number of sunspots. The maintenance of such a solar magnetic field can be attributed to fluid motion in the convection zone, i.e. a dynamo. This study conducts the…

Solar and Stellar Astrophysics · Physics 2022-08-24 Ryota Shimada , Hideyuki Hotta , Takaaki Yokoyama

Variations in the geomagnetic field occur on a vast range of time scales, from milliseconds to millions of years. The advent of satellite measurements has allowed for detailed studies of the short timescale geomagnetic field behaviour, but…

Geophysics · Physics 2022-11-30 Daria Holdenried-Chernoff , David A. King , Bruce A. Buffett

Detailed study of the solar magnetic field is crucial to understand its generation, transport and reversals. The timing of the reversals may have implications on space weather and thus identification of the temporal behavior of the critical…

We considered variations the dipole and the quadrupole components of the solar large-scale magnetic field. Both the axial and the equatorial dipoles exhibit a systematic decrease in the past four cycles in accordance with the general…

Solar and Stellar Astrophysics · Physics 2020-02-19 V. N. Obridko , D. D. Sokoloff , B. D. Shelting , A. S. Shibalova , I. M. Livshits

Off-centred dipole configurations have been suggested to explain different phenomena in neutron stars, such as natal kicks, irregularities in polarisation of radio pulsars and properties of X-ray emission from millisecond pulsars. Here for…

High Energy Astrophysical Phenomena · Physics 2023-08-21 Andrei P. Igoshev , Rainer Hollerbach , Toby Wood