Monika Korte

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

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Co-Authors

Catherine Constable

Scripps Institution of Oceanography

Mioara Mandéa

Centre National d'Études Spatiales

Steven Grahame Moreton

Scottish Universities Environmental Research Centre

Barbara A. Maher

Lancaster University

James A Smith

British Antarctic Survey

Gerhard Kühn

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

Claus‐Dieter Hillenbrand

British Antarctic Survey

Robert D Larter

British Antarctic Survey

Rainer Gersonde

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

Oliver Esper

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

Cooperative Institutions

Charles River Laboratories (Netherlands)

334

John Wiley & Sons (United States)

320

Centre National de la Recherche Scientifique

Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences

Planetary Science Institute

Space Science Institute

Goddard Space Flight Center

Nagoya University

University of Colorado Boulder

Kyoto University

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Regional millennial trend in the cosmic ray induced ionization of the troposphere

Journal of Atmospheric and Solar-Terrestrial Physics (2009)

Ilya Usoskin Irina Mironova Monika Korte G. A. Kovaltsov

10.1016/j.jastp.2009.10.003

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Citations (37)

Validity of archaeomagnetic field recording: an experimental pottery kiln at Coppengrave, Germany

Geophysical Journal International (2016)

Elisabeth Schnepp Roman Leonhardt Monika Korte Johannes Klett-Drechsel

Palaeomagnetic data obtained from archaeological materials are used for reconstructions of the Earth's magnetic field of the past millennia. While many studies tested the reliability of this recorder for palaeointensity only a few studies did this for direction. The study presents an archaeomagnetic and rock magnetic investigation applied to an experimental pottery kiln, which was operated in 2003 to produce stone ware. This kind of high-quality pottery needs a temperature of at least 1160 °C. Shortly before heating of the kiln direct absolute measurements of the absolute geomagnetic field vector have been carried out close to it. After cooling of the kiln 24 oriented palaeomagnetic samples have been taken. Although Curie temperatures are about 580 °C, that is the typical temperature for magnetite, thermal as well as alternating field demagnetisations reveal also a considerable amount of hematite as magnetic carrier. This mixture of magnetite and hematite is dominated by pseudo-single domain grains. Demagnetisation removed in some cases weak secondary components, but in most cases the specimens carried a single component thermoremanent magnetisation. The mean characteristic remanent magnetisation direction agrees on 95 per cent confidence level with the directly measured field direction. Archaeointensity was obtained from five specimens with the Thellier-Coe method and with the multiple-specimen palaeointensity domain-state corrected method. Six of these specimens also provided a result of the Dekkers-Böhnel method, which overestimated the archaeointensity by about 9 per cent compared to the direct value, while after correction for fraction the value agrees very well. For the multiple-specimen palaeointensity domain-state corrected method only fractions between 25 and 75 per cent have been used and specimens showing alteration have been excluded. Above 450 °C many specimens showed alteration of the magnetic grains. Because median destructive temperatures were often above this value in most cases the fraction was less than 50 per cent. Nevertheless the obtained intensity (48.48 ± 0.24 μ) is on 95 per cent confidence level in agreement with the direct observation. Behaviour of the specimens during the Thellier-experiments was not ideal because of narrow unblocking temperature spectra and alteration. Nevertheless, the obtained mean archaeointensity is also in agreement with the direct field observation. Here the relative palaeointensity error is about 6 per cent and very high compared the multiple-specimen palaeointensity domain-state corrected method. The investigation demonstrates that a pottery kiln can provide a very precise estimate of the ancient geomagnetic field vector.

Archaeomagnetic dating

Magnetic mineralogy

Thermoremanent magnetization

Rock magnetism

10.1093/gji/ggw043

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Citations (17)

Advances in archaeomagnetic dating in Britain: New data, new approaches and a new calibration curve

Journal of Archaeological Science (2017)

C. M Batt M. C. Brown S. Clelland Monika Korte Paul Linford

Archaeomagnetic dating offers a valuable chronological tool for archaeological investigations, particularly for dating fired material. The method depends on the establishment of a dated record of secular variation of the Earth's magnetic field and this paper presents new and updated archaeomagnetic directional data from the UK and geomagnetic secular variation curves arising from them. The data are taken from publications from the 1950's to the present day; 422 dated entries derived from existing archaeo and geomagnetic databases are re-evaluated and 487 new directions added, resulting in 909 entries with corresponding dates, the largest collection of dated archaeomagnetic directions from a single country. An approach to improving the largest source of uncertainty, the independent dating, is proposed and applied to the British Iron Age, resulting in 145 directions from currently available databases being updated with revised ages and/or uncertainties, and a large scale reassessment of age assignments prior to inclusion into the Magnetic Moments of the Past and GEOMAGIA50 databases. From the significantly improved dataset a new archaeomagnetic dating curve for the UK is derived through the development of a temporally continuous geomagnetic field model, and is compared with previous UK archaeomagnetic dating curves and global field models. The new model, ARCH-UK.1 allows model predictions for any location in the UK with associated uncertainties. It is shown to improve precision and accuracy in archaeomagnetic dating, and to provide new insight into past geomagnetic field changes.

Archaeomagnetic dating

Secular Variation

Geomagnetic secular variation

Variation (astronomy)

10.1016/j.jas.2017.07.002

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Citations (35)

Sedimentary record of the western Amundsen Sea Embayment after the last glacial maximum

Claus‐Dieter Hillenbrand James A Smith Gerhard Kühn Oliver Esper Rainer Gersonde

Last Glacial Maximum

10.1594/pangaea.715974

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Correlation based snapshot models of the archeomagnetic field

Geophysical Journal International (2020)

Stefan Mauerberger Maximilian Arthus Schanner Monika Korte M. Holschneider

SUMMARY For the time stationary global geomagnetic field, a new modelling concept is presented. A Bayesian non-parametric approach provides realistic location dependent uncertainty estimates. Modelling related variabilities are dealt with systematically by making little subjective a priori assumptions. Rather than parametrizing the model by Gauss coefficients, a functional analytic approach is applied. The geomagnetic potential is assumed a Gaussian process to describe a distribution over functions. A priori correlations are given by an explicit kernel function with non-informative dipole contribution. A refined modelling strategy is proposed that accommodates non-linearities of archeomagnetic observables: First, a rough field estimate is obtained considering only sites that provide full field vector records. Subsequently, this estimate supports the linearization that incorporates the remaining incomplete records. The comparison of results for the archeomagnetic field over the past 1000 yr is in general agreement with previous models while improved model uncertainty estimates are provided.

10.1093/gji/ggaa336

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Citations (10)

Documentation of sediment core PS69/274-1

Alfred Wegener Institute - Polarstern core repository (2010)

Claus‐Dieter Hillenbrand James A Smith Gerhard Kühn Oliver Esper Rainer Gersonde

Sediment core

10.1594/pangaea.499835

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Citations (0)

Evolution of Large‐Scale Magnetic Fields From Near‐Earth Space During the Last 11 Solar Cycles

Journal of Geophysical Research Space Physics (2019)

Leonie Pick Monika Korte Yannik Thomas N. A. Krivova Chi‐Ju Wu

Abstract We use hourly mean magnetic field measurements from 34 midlatitude geomagnetic observatories between 1900 and 2015 to investigate the long‐term evolution and driving mechanism of the large‐scale external magnetic field at ground. The Hourly Magnetospheric Currents index (HMC) is derived as a refinement of the Annual Magnetospheric Currents index (HMC, Pick & Korte, 2017, https://doi.org/10.1093/gji/ggx367 ). HMC requires an extensive revision of the observatory hourly means. It depends on three third party geomagnetic field models used to eliminate the core, the crustal, and the ionospheric solar‐quiet field contributions. We mitigate the dependency of HMC on the core field model by subtracting only nondipolar components of the model from the data. The separation of the residual (dipolar) signal into internal and external (HMC) parts is the main methodological challenge. Observatory crustal biases are updated with respect to AMC, and the solar‐quiet field estimation is extended to the past based on a reconstruction of solar radio flux (F10.7). We find that HMC has more power at low frequencies (periods ≥ 1 year) than the Dcx index, especially at periods relevant to the solar cycle. Most of the slow variations in HMC can be explained by the open solar magnetic flux. There is a weakly decreasing linear trend in absolute HMC from 1900 to present, which depends sensitively on the data rejection criteria at early years. HMC is well suited for studying long‐term variations of the geomagnetic field.

Space Weather

QUIET

Ionospheric dynamo region

Solar observatory

10.1029/2018ja026185

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Citations (8)

Issue Information

Geophysical Research Letters (2018)

Noah S. Diffenbaugh Suzana J. Camargo Mónica Cárdenas R. Carey Rose M. Cory

No abstract is available for this article.

10.1002/grl.56391

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Citations (0)

Persistent westward drift of the geomagnetic field at the core–mantle boundary linked to recurrent high-latitude weak/reverse flux patches

Geophysical Journal International (2020)

Andreas Nilsson Neil Suttie Monika Korte R. Holme Mimi J. Hill

SUMMARY Observations of changes in the geomagnetic field provide unique information about processes in the outer core where the field is generated. Recent geomagnetic field reconstructions based on palaeomagnetic data show persistent westward drift at high northern latitudes at the core–mantle boundary (CMB) over the past 4000 yr, as well as intermittent occurrence of high-latitude weak or reverse flux patches. To further investigate these features, we analysed time-longitude plots of a processed version of the geomagnetic field model pfm9k.1a, filtered to remove quasi-stationary features of the field. Our results suggest that westward drift at both high northern and southern latitudes of the CMB have been a persistent feature of the field over the past 9000 yr. In the Northern Hemisphere we detect two distinct signals with drift rates of 0.09° and 0.25° yr−1 and dominant zonal wavenumbers of m = 2 and 1, respectively. Comparisons with other geomagnetic field models support these observations but also highlight the importance of sedimentary data that provide crucial information on high-latitude geomagnetic field variations. The two distinct drift signals detected in the Northern Hemisphere can largely be decomposed into two westward propagating waveforms. We show that constructive interference between these two waveforms accurately predicts both the location and timing of previously observed high-latitude weak/reverse flux patches over the past 3–4 millennia. In addition, we also show that the 1125-yr periodicity signal inferred from the waveform interference correlates positively with variations in the dipole tilt over the same time period. The two identified drift signals may partially be explained by the westward motion of high-latitude convection rolls. However, the dispersion relation might also imply that part of the drift signal could be caused by magnetic Rossby waves riding on the mean background flow.

Core–mantle boundary

Geomagnetic secular variation

Secular Variation

Longitude

10.1093/gji/ggaa249

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Citations (16)

Application of factor analysis in electron spectroscopic depth profiling on copper oxide

Analytica Chimica Acta (1994)

H. Bubert Monika Korte R. P. H. Garten E. Grallath M. Wieluński

Copper oxide

Nuclear reaction analysis

10.1016/0003-2670(94)00053-0

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Citations (9)