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  • 1
    Call number: 5/M 11.0052
    In: IAGA special Sopron book series
    Description / Table of Contents: This volume provides comprehensive and authoritative coverage of all the main areas linked to geomagnetic field observation, from instrumentation to methodology, on ground or near-Earth. Efforts are also focused on a 21st century e-Science approach to open access to all geomagnetic data, but also to the data preservation, data discovery, data rescue, capacity building. Finally, modeling magnetic fields with different internal origins, with their variation in space and time, is an attempt to draw together into one place the traditional work in producing models as IGRF or describing the magnetic anomalies.
    Type of Medium: Monograph available for loan
    Pages: XV, 343 S. , zahlr. Ill., graph. Darst., Kt.
    ISBN: 9789048198573
    Series Statement: IAGA special Sopron book series 5
    Classification:
    Geomagnetism, Geoelectromagnetism
    Location: Reading room
    Branch Library: GFZ Library
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  • 2
    Call number: 21/M 07.0460
    Type of Medium: Monograph available for loan
    Pages: 26 S.
    Series Statement: Sonderveröffentlichungen / Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum
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  • 3
    GFZ publications
    GFZ publications
    Potsdam : GeoForschungsZentrum
    Associated volumes
    Call number: 21/STR 01/04
    In: Scientific technical report
    Type of Medium: GFZ publications
    Pages: 23 S..
    Series Statement: Scientific technical report / Geoforschungszentrum Potsdam 01/04
    Classification:
    Geomagnetism, Geoelectromagnetism
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  • 4
    Call number: 21/STR 99/11
    In: Scientific technical report
    Type of Medium: GFZ publications
    Pages: 100 S.
    Series Statement: Scientific Technical Report / Geoforschungszentrum Potsdam 99/11
    Classification:
    Geomagnetism, Geoelectromagnetism
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  • 5
    Call number: 5/M 20.93402
    Type of Medium: Monograph available for loan
    Pages: xiii, 331 Seiten , Graphiken
    ISBN: 978-1-108-41848-5
    Series Statement: Special publications of the International Union of Geodesy and Geophysics
    Classification:
    Geomagnetism, Geoelectromagnetism
    Language: English
    Branch Library: GFZ Library
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  • 6
    Publication Date: 2023-08-24
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Polarity reversals and excursions are the most significant geomagnetic field changes generated in the liquid outer core of the Earth, therefore studying them helps understand geodynamo processes. This study examines the Matuyama‐Brunhes (MB) reversal using a new reconstruction of the global geomagnetic field based on paleomagnetic data, termed Global Geomagnetic Field Model for the MB reversal (GGFMB). GGFMB covers 900–700 ka, including late Matuyama and early Brunhes. This allows us to also investigate the Kamikatsura excursion (ca. 888 ka). The model is based on 38 high‐quality paleomagnetic sediment records with age control mostly independent of the magnetic signal. GGFMB suggests that the MB reversal began about ∼799 ka, when non‐dipole field components increased and the axial dipole component decreased. The transitional fields first appeared on Earth's surface in the high‐latitude southern hemisphere and equatorial regions. The minimum dipole strength was reached around 780 ka and the axial dipole changed sign. After ∼10 Kyr, the field stabilized in the normal polarity of the early Brunhes. The MB reversal lasted ∼29 Kyr (from 799 to 770 ka) and had slower rate of dipole decay than recovery as well as lower dipole moment for several millennia before than after the reversal. According to GGFMB, the dipole moment during the Kamikatsura excursion was approximately half that of the current field and it was a regional excursion observed only over eastern Asia and North America. Our sediment data collection is heavily biased toward the northern hemisphere, thus more southern hemisphere records are needed to demonstrate GGFMB's robustness in this region.〈/p〉
    Description: Plain Language Summary: The Earth's magnetic field originates deep inside the planet and extends far into space, and it has undergone significant direction and intensity changes throughout geological history. The most extreme magnetic field changes are reversals, when the field changes its polarity and global field intensity reaches a minimum. We reconstruct the global geomagnetic field evolution over the time interval 900,000 to 700,000 years ago. The information about the magnetic field variations comes from the paleomagnetic signal recovered from sediment drill cores from locations all over the globe, and with good constraints on the ages of the material. Our model includes the Matuyama‐Brunhes field reversal, which occurred ∼780,000 years ago. It provides a global view of this drastic field change, indicating, for example, that the recovery of the global field intensity was much faster than its decay and the average global field strength was lower for several millennia before than after the polarity change. Our model suggests that the reversal started at ∼799 ka, the actual polarity change of the axial dipole field occurred at ∼780 ka, and a stable normal polarity was reached at ∼770 ka. The whole process of the reversal therefore took ∼29,000 years.〈/p〉
    Description: Key Points: A global geomagnetic field model for 900–700 ka is presented, including the Matuyama‐Brunhes (MB) reversal and Kamikatsura excursion. The mid‐point of the Matuyama‐Brunhes reversal is at 780 ka, with an overall duration of nearly 30 Kyr. The dipole field decays from moderate dipole moment in the late Matuyama and recovers quickly to higher values in the early Brunhes.
    Description: Helmholtz‐Zentrum Potsdam ‐ Deutsches GeoForschungsZentrum GFZ http://dx.doi.org/10.13039/501100010956
    Description: https://earthref.org/ERDA/2548/
    Description: https://earthref.org/ERDA/2548/
    Keywords: ddc:538.7 ; geomagnetic field model ; Matuyama-Brunhes (MB) reversal ; Kamikatsura excursion
    Language: English
    Type: doc-type:article
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  • 7
    Publication Date: 2023-11-18
    Description: Magnetic field reversals are irregular events in Earth's history when the geomagnetic field changes its polarity. Reversals are recorded by spot and continuous remanent magnetization data collected from lava flows and marine sediments, respectively. The latest field reversal, the Matuyama‐Brunhes reversal (MBR), is better covered by paleomagnetic data than prior field reversals, hence providing an opportunity to understand the physical mechanisms. Despite the quantity of data, a full understanding of the MBR is still lacking. The evolution of the MBR in time and space is explored in this work by compiling a global set of paleomagnetic data, both from sediments and volcanic rocks, which encompass the period 900–700 ka. After careful evaluation of data and dating quality, regional and global stacks of virtual axial dipole moment (VADM), virtual geomagnetic pole (VGP), and paleosecular variation index (Pi) are constructed from the sediment records using bootstrap resampling. Individual VADMs and VGPs calculated from lavas are compared to these stacks. Four phases of full‐vector field instability are observed in these stacks over the period 800–770 ka. The first three phases, observed at 800–785 ka, reflect a rapid weakening of the field coupled with low VGP latitude, after which the field returned to the reverse polarity of the Matuyama chron. The fourth phase, lasting from 780 to 770 ka, is when the field reversal process completed, such that the field entered the Brunhes normal polarity state. These findings point to a complex reversal process lasting ∼30 Kyr, with the reversal ending at ∼770 ka.
    Description: Plain Language Summary: The Earth's magnetic field, or geomagnetic field, which humans and some animals use for navigation, shields us from solar and cosmic radiation. The magnetic North and South poles have repeatedly, but infrequently changed their positions over Earth's history, a phenomenon known as magnetic field reversal. During a reversal, the magnetic field intensity decreased to low levels, which could have had a detrimental impact on our planet as the magnetic shielding is diminished. The magnetic field last switched polarity from the Matuyama reverse state to the current Brunhes normal polarity in the most recent field reversal. This work used regional and global stacks of paleomagnetic sediment records with reasonable age control, to investigate the Matuyama‐Brunhes reversal. From these stacks, we find that the last field reversal took ∼30 Kyr to evolve, beginning at about 800 ka and ending at around 770 ka. Our data compilation indicates that the reversal lasted longer in records from high latitudes than low‐ to mid latitudes records, which confirms a previous suggestion that local reversal duration is latitudinal dependent.
    Description: Key Points: Global characteristics of the Matuyama‐Brunhes field reversal were examined from well‐dated high‐quality lava and marine core data. The Matuyama‐Brunhes reversal started at 800 ka and the whole process lasted 30 ka. The new data compilation generally confirms longer regional reversal duration at high latitudes compared to low latitudes.
    Description: Alexander von Humboldt Foundation http://dx.doi.org/10.13039/501100010956
    Description: Discovery Fellowship, GFZ Potsdam, Germany.
    Description: https://earthref.org/ERDA/2545/
    Keywords: ddc:538.7 ; paleomagnetic sediment records ; Matuyama-Brunhes geomagnetic field reversal
    Language: English
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  • 8
    Publication Date: 2023-12-14
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The production rates of cosmogenic radionuclides, such as 〈sup〉10〈/sup〉Be, 〈sup〉14〈/sup〉C, and 〈sup〉36〈/sup〉Cl, in the Earth's atmosphere vary with the geomagnetic field and solar activity. For the first time, the production rates of several cosmogenic nuclides are estimated for the past 100 ka based on global, time‐dependent geomagnetic field models and a moderate solar‐activity level. In particular, the production rates were high with no notable latitudinal dependence during the Laschamps geomagnetic excursion (41 ka BP). The mean global production of 〈sup〉10〈/sup〉Be over the Laschamps excursion was more than two times greater than the present‐day one, whereas the increase was 1.9 times for the Norwegian‐Greenland Sea excursion (∼65 ka), and only 1.3 times for the Mono Lake/Auckland excursion (∼34 ka). All analyzed geomagnetic field models covering the past 100 ka, including the modern and Holocene epochs, lead to hemispheric asymmetry in the production rates, persistent overall time ranges, and reflected in the time‐averaged nuclide production rates. Production rates predicted by the geomagnetic field models are in good agreement with actual measurements from ice cores and sediment records. These global, long‐term production rates are important for a wide range of studies that employ cosmogenic nuclides as a proxy/tracer of different Earth system processes.〈/p〉
    Description: Key Points: 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉We estimated the atmospheric production rates of cosmogenic radionuclides using global geomagnetic field models covering the past 100 ka〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉The results show the importance of the multipolar components of the field during the Laschamps excursion〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉The variations in production rates predicted by the models agree well with the actual measurements from ice cores〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: Academy of Finland http://dx.doi.org/10.13039/501100002341
    Description: University of Oulu
    Description: China Scholarship Council http://dx.doi.org/10.13039/501100004543
    Description: Helmholtz‐Zentrum Potsdam ‐ Deutsches GeoForschungsZentrum GFZ http://dx.doi.org/10.13039/501100010956
    Description: https://earthref.org/ERDA/2543/
    Description: https://earthref.org/ERDA/2498/
    Description: https://earthref.org/ERDA/2521/
    Keywords: ddc:538.7 ; cosmogenic isotopes ; production rates ; geomagnetic field ; geomagnetic excursions ; Laschamps event
    Language: English
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  • 9
    Publication Date: 2018-04-30
    Description: The geomagnetic field has been decaying at a rate of ∼5% per century from at least 1840, with indirect observations suggesting a decay since 1600 or even earlier. This has led to the assertion that the geomagnetic field may be undergoing a reversal or an excursion. We have derived a model of the geomagnetic field spanning 30–50 ka, constructed to study the behavior of the two most recent excursions: the Laschamp and Mono Lake, centered at 41 and 34 ka, respectively. Here, we show that neither excursion demonstrates field evolution similar to current changes in the geomagnetic field. At earlier times, centered at 49 and 46 ka, the field is comparable to today’s field, with an intensity structure similar to today’s South Atlantic Anomaly (SAA); however, neither of these SAA-like fields develop into an excursion or reversal. This suggests that the current weakened field will also recover without an extreme event such as an excursion or reversal. The SAA-like field structure at 46 ka appears to be coeval with published increases in geomagnetically modulated beryllium and chlorine nuclide production, despite the global dipole field not weakening significantly in our model during this time. This agreement suggests a greater complexity in the relationship between cosmogenic nuclide production and the geomagnetic field than is commonly assumed.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 10
    Publication Date: 2018-05-15
    Description: Thank you to those who reviewed in 2017 for Geophysical Research Letters. ©2018. American Geophysical Union. All Rights Reserved.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
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