Paleomagnetic reconstruction of the global geomagnetic field evolution during the Matuyama/Brunhes transition: Iterative Bayesian inversion and independent verification

Leonhardt, Roman; Fabian, Karl

doi:10.1016/j.epsl.2006.10.025

Cited by 115 publications

(176 citation statements)

References 51 publications

Supporting

Mentioning

162

Contrasting

Order By: Relevance

“…Common to most reversal simulations is the importance of strong inverse magnetic field patches at low to mid latitudes in the beginning phase of a reversal (Driscoll and Olson 2009). This agrees with the findings in the paleomagnetic model for the Matuyama-Bruñes reversal by Leonhardt and Fabian (2007). Busse and Simitev (2008) describe a completely different reversal scenario which is based on a Parker dynamo wave: inverse field starts to grow on either side of the equatorial plane and propagates towards the poles (Parker 1955;.…”

Section: Reversals Mechanismssupporting

confidence: 89%

Theory and Modeling of Planetary Dynamos

Wicht

Tilgner

2010

Space Sci Rev

View full text Add to dashboard Cite

Numerical dynamo models are increasingly successful in modeling many features of the geomagnetic field. Moreover, they have proven to be a useful tool for understanding how the observations connect to the dynamo mechanism. More recently, dynamo simulations have also ventured to explain the surprising diversity of planetary fields found in our solar system. Here, we describe the underlying model equations, concentrating on the Boussinesq approximations, briefly discuss the numerical methods, and give an overview of existing model variations. We explain how the solutions depend on the model parameters and introduce the primary dynamo regimes. Of particular interest is the dependence on the Ekman number which is many orders of magnitude too large in the models for numerical reasons. We show that a minor change in the solution seems to happen at E = 3×10 −6 whose significance, however, needs to be explored in the future. We also review three topics that have been a focus of recent research: field reversal mechanisms, torsional oscillations, and the influence of Earth's thermal mantle structure on the dynamo. Finally we discuss the possibility of tidally or precession driven planetary dynamos.

show abstract

Section: Reversals Mechanismssupporting

confidence: 89%

Theory and Modeling of Planetary Dynamos

Wicht

Tilgner

2010

Space Sci Rev

View full text Add to dashboard Cite

show abstract

“…All these results are in agreement with early stages of a dipole collapse in the numerical dynamo model by Olson et al (2009). In a detailed study of the Matuyama-Brunhes polarity reversal (Leonhardt and Fabian, 2007) and Laschamp excursion (Leonhardt et al, 2009) the field instability starts when reverse flux patches appear in low or mid latitude regions at the CMB and then move poleward. In contrast, Aubert et al (2008) found a mixed behavior, with reversals and excursions initiated by reversed flux generated both outside and inside the tangent cylinder.…”

Section: Introductionsupporting

confidence: 81%

Toward a possible next geomagnetic transition?

Santis

Qamili

2013

Nat. Hazards Earth Syst. Sci.

View full text Add to dashboard Cite

Abstract. The geomagnetic field is subject to possible reversals or excursions of polarity during its temporal evolution. Considering that: (a) in the last 83 million yr the typical average time between one reversal and the next (the so-called chron) is around 400 000 yr, (b) the last reversal occurred around 780 000 yr ago, (c) more excursions (rapid changes in polarity) can occur within the same chron and (d) the geomagnetic field dipole is currently decreasing, a possible imminent geomagnetic reversal or excursion would not be completely unexpected. In that case, such a phenomenon would represent one of the very few natural hazards that are really global. The South Atlantic Anomaly (SAA) is a great depression of the geomagnetic field strength at the Earth's surface, caused by a reverse magnetic flux in the terrestrial outer core. In analogy with critical point phenomena characterized by some cumulative quantity, we fit the surface extent of this anomaly over the last 400 yr with power law or logarithmic functions in reverse time, also decorated by logperiodic oscillations, whose final singularity (a critical point t c ) reveals a great change in the near future (2034 ± 3 yr), when the SAA area reaches almost a hemisphere. An interesting aspect that has recently been found is the possible direct connection between the SAA and the global mean sea level (GSL). That the GSL is somehow connected with SAA is also confirmed by the similar result when an analogous critical-like fit is performed over GSL: the corresponding critical point (2033 ± 11 yr) agrees, within the estimated errors, with the value found for the SAA. From this result, we point out the intriguing conjecture that t c would be the time of no return, after which the geomagnetic field could fall into an irreversible process of a global geomagnetic transition that could be a reversal or excursion of polarity.

show abstract

“…Whether this feature plays a dynamical role in the reversal of the dipole, or whether it is simply a consequence of the polar dipole component being small (allowing higher-degree modes to dominate), remains at issue. We note in passing that similar dominance by the quadrupolar over the dipolar modes is observed during reversals of the geomagnetic field, and indeed interplay between these low-degree modes have been hypothesized to trigger polarity reversals for the earth's magnetic field (McFadden et al 1991;Leonhardt & Fabian 2007).…”

Section: Discussion and Concluding Remarkssupporting

confidence: 56%

Dipolar and Quadrupolar Magnetic Field Evolution over Solar Cycles 21, 22, and 23

DeRosa

Brun²,

Hoeksema

2010

Proc. IAU

View full text Add to dashboard Cite

Abstract. Time series of photospheric magnetic field maps from two observatories, along with data from an evolving surface-flux transport model, are decomposed into their constituent spherical harmonic modes. The evolution of these spherical harmonic spectra reflect the modulation of bipole emergence rates through the solar activity cycle, and the subsequent dispersal, shear, and advection of magnetic flux patterns across the solar photosphere. In this article, we discuss the evolution of the dipolar and quadrupolar modes throughout the past three solar cycles (Cycles 21-23), as well as their relation to the reversal of the polar dipole during each solar maximum, and by extension to aspects of the operation of the global solar dynamo.

show abstract

Paleomagnetic reconstruction of the global geomagnetic field evolution during the Matuyama/Brunhes transition: Iterative Bayesian inversion and independent verification

Cited by 115 publications

References 51 publications

Theory and Modeling of Planetary Dynamos

Theory and Modeling of Planetary Dynamos

Toward a possible next geomagnetic transition?

Dipolar and Quadrupolar Magnetic Field Evolution over Solar Cycles 21, 22, and 23

Contact Info

Product

Resources

About