ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Publication Date: 2017-04-04
    Description: We propose a new geomagnetic field model for the Holocene period based on archaeomagnetic and lava flow data, avoiding the use of lake sediment data. The source of data comes from the GEOMAGIA50v2 database which has been updated with the new archaeomagnetic and volcanic studies published during the last 3 years. The model, called SHA.DIF.14k, allows us to analyse the behaviour of the geomagnetic field for the last 14000 years: from 12000 BC to 1900 AD. For the model construction we use the spherical harmonic analysis in space and the penalized cubic B-splines in time. Both spatial and temporal regularization norms are used to constrain the inversion problem and applied at the core-mantle boundary (CMB) to assure the convergence of the model. For the last 3ka, the model predictions agree with those given by the global model ARCH3k.1 and the European model SCHA.DIF.3k. For older epochs, the new model presents a clear improvement in field resolution with respect to other current models of the geomagnetic field for the Holocene. For the last 9ka, the time evolution of the dipolar moment obtained from the dipole field shows a clear minimum between 5500 BC and 3000 BC, and the well-known continuous decreasing trend of the geomagnetic field strength for the last millennium and half. A general view of the time-average evolution of the geomagnetic field flux lobes at the CMB for the northern hemisphere suggests a marked lobe of positive magnetic flux when the dipole moment was maximum. This lobe vanishes when the dipolar field is decreasing. The north polar wander paths of both north magnetic dip and geomagnetic poles were obtained showing an average rate of motion of 5.1 km/yr and 3.7 km/yr respectively. The model shows that the geomagnetic field can be averaged as axial dipolar in ~2000 years within an error of 5º, the typical uncertainty of the palaeomagnetic studies. Finally, and following the recent definition of archaeomagnetic jerks, we found 8 critical events in the time-evolution of the geomagnetic field for the last 8ka characterized by a maximum in the hemispheric asymmetry of the proposed model. The model is available in the Earth Ref Digital Archive at http://earthref.org/ERDA/1897/.
    Description: Published
    Description: 98-109
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: geomagnetism ; archaeomagnetism ; geomagnetic field model ; secular variation ; holocene ; 04. Solid Earth::04.05. Geomagnetism::04.05.01. Dynamo theory ; 04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals ; 04. Solid Earth::04.05. Geomagnetism::04.05.03. Global and regional models ; 04. Solid Earth::04.05. Geomagnetism::04.05.05. Main geomagnetic field ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 2019-03-14
    Description: Since the pioneering studies in archeomagnetism in the second half of the 20th century, the number of archeomagnetic studies has increased exponentially. The huge density of archeomagnetic data collected during these years allows us to describe the past spatial and temporal evolution of the Earth’s magnetic field during the last millennia. Most of the data are located in the Northern Hemisphere, but currently, thanks to the strong effort of the paleomagnetic community, new collections of data are coming from the Southern Hemisphere, homogenizing the present database. Although the data distribution presents some epochs and locations where the data are still very scarce, they describe, to a greater or lesser degree of accuracy, the past behavior of the geomagnetic field. At regional scales, the use of archeomagnetic data permits the construction of paleosecular variation curves for the geomagnetic field elements: declination, inclination, and intensity. These curves describe the evolution of the elements at different times for the last millennia. During the last five years novel techniques, such as Bayesian statistics, bootstrap algorithms, or the Markov chain Monte Carlo method, have been applied to extract the most useful information from archeomagnetic data to build accurate and reliable curves. The accuracy of these curves can be exploited as a tool for archeomagnetic dating, assigning possible ages to archeological artifacts or volcanic lava flows with unknown age. At global scales, archeomagnetic data are jointly treated with other paleomagnetic data to generate continuous geomagnetic field models, reconstructing the past evolution of the geomagnetic field not only at the Earth’s surface, but also at the core-mantle boundary, shedding light on the past evolution of complex geodynamo processes.
    Description: Published
    Description: 99-158
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: restricted
    Keywords: Archeomagnetism ; Paleomagnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals ; 04. Solid Earth::04.05. Geomagnetism::04.05.03. Global and regional models ; 04. Solid Earth::04.05. Geomagnetism::04.05.05. Main geomagnetic field ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.07. Rock magnetism ; 04. Solid Earth::04.05. Geomagnetism::04.05.08. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2019-03-14
    Description: The study of the temporal evolution of the dipole moment variations is a forefront research topic in Earth sciences. It constrains geodynamo simulations and is used to correct cosmogenic isotope production, which is evidence of past solar activity, and it is used to study possible correlations between the geomagnetic field and the climate. In this work, we have analysed the main error sources in the geomagnetic dipole moment computation from palaeomagnetic data: the influence of the non-dipole terms in the average approach, the inhomogeneous distribution of the current palaeomagnetic database, and the averaging procedure used to obtain the evolution of the dipole moment. To evaluate and quantify these effects, we have used synthetic data from a global model based on instrumental and satellite data, the International Geomagnetic Reference Field: 11th generation. Results indicate that the non-dipole terms contribute on a global scale of 〈6% in the averaged dipole moment, whereas the regional non-dipole contribution can show deviations of up to 35 % in some regions such as Oceania, and different temporal trends with respect to the global dipole moment evolution in other ones, such as Europe and Asia. A regional weighting scheme seems the best option to mitigate these effects in the dipole moment average approach. But when directional and intensity palaeomagnetic information is available on a global scale, and in spite of the inhomogeneity of the database, global modelling presents more reliable values of the geomagnetic dipole moment.
    Description: Published
    Description: 91-107
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: geomagnetism ; paleomagnetism ; archeomagnetism ; geomagnetic dipole moment ; geomagnetic field modelling ; 04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals ; 04. Solid Earth::04.05. Geomagnetism::04.05.03. Global and regional models ; 04. Solid Earth::04.05. Geomagnetism::04.05.05. Main geomagnetic field ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...