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  • Geomagnetic field  (6)
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  • 1
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    Are we going towards a global planetary magnetic change? (2008)
    World Scientific and Engineering Academy and Society Press
    Details
    Publication Date: 2017-04-04
    Description: The dipolar part of the geomagnetic field has been decaying rapidly during the last few hundreds of years. In addition to this classical argument, from Information theory applied to geomagnetism, there are some evidences that the recent Earth magnetic field is showing characteristics typical of a reversal in progress. If this is true, many scientific and environmental questions will arise. For instance, it will be of particular interest to monitor the time-space dynamics the South Atlantic Anomaly, where the magnetic field is strongly reduced (a sort of "planetary magnetic hole"). Here we find one of the most favourite places where Low Earth Orbiting (LEO) satellites are lost or present some damages, due to the vicinity of "clouds" of electric particles (Van Allen belts) to the Earth's surface. The decay of the field will also decrease the screening effect to the solar wind and cosmic charges, so enhancing the cosmic radiation illuminating our planet: possible negative consequences are expected in terms of increase of skin cancers. Also important will be the study of the possible evolution of the core dynamics that will be generating this specific condition of the geomagnetic field.
    Description: Published
    Description: Malta, September 11-13, 2008
    Description: 1.6. Osservazioni di geomagnetismo
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: 3.4. Geomagnetismo
    Description: open
    Keywords: Geomagnetic field ; Geomagnetic reversal ; Global Change ; Information theory ; Shannon information ; 04. Solid Earth::04.01. Earth Interior::04.01.03. Mantle and Core dynamics ; 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::04.05.05. Main geomagnetic field ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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  • 2
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    How persistent is the present trend of the geomagntic field to decay and, possibly, to reverse? (2007)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: Recent studies provide evidence for a possible imminent change of polarity or an excursion of the geomagnetic field. In this paper we explore the possibility that the present trends are persistent, looking at the behaviour of some physical quantities of the recent geomagnetic field with particular attention to the last century. Analysis of the mean square value of the field over the last 400 years shows a linear decay that if extrapolated will be zero in around 1000 years, while if we extrapolate the field over Antarctica it will go to zero in around 300 years. The information content of the geomagnetic field has been decaying from around 1690, but began to decrease more rapidly at around 1775 and even more rapidly after 1900. An intermittent synchronicity between the exponential field decay and the increase latitudinal speed of the south geomagnetic pole with similar (decaying or growing) timescales can be interpreted as evidence for a present persistent turbulence of the geomagnetic field. From this work it emerges that the present situation is likely to persist further into the future, probably for another century, but longer predictions are not possible.
    Description: Published
    Description: 217-226
    Description: 3.4. Geomagnetismo
    Description: JCR Journal
    Description: reserved
    Keywords: Geomagnetic field ; geomagnetic reversal ; persistent turbolence ; 04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    Ergodicity of the recent geomagnetic field (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: The geomagnetic field is a fundamental property of our planet: its study would allow us to understand those processes of Earth’s interior, which act in its outer core and produce the main field. Knowledge of whether the field is ergodic, i.e. whether time averages correspond to phase space averages, is an important question since, if this were true, it would point out a strong spatio-temporal coupling amongst the components of the dynamical system behind the present geomagnetic field generation. Another consequence would be that many computations, usually undertaken with many difficulties in the phase space, can be made in the conventional time domain. We analyse the temporal behaviour of the deviation between predictive and definitive geomagnetic global models for successive intervals from 1965 to 2010, finding a similar exponential growth with time. Also going back in time (at around 1600 and 1900 by using the GUFM1 model) confirms the same findings. This result corroborates previous chaotic analyses made in a reconstructed phase space from geomagnetic observatory time series, confirming the chaotic character of the recent geomagnetic field with no reliable prediction after around 6 years from definitive values, and disclosing the potentiality of estimating important entropic quantities of the field by time averages. Although more tests will be necessary, some of our analyses confirm the efforts to improve the representation of the geomagnetic field with more detailed secular variation and acceleration.
    Description: Published
    Description: 103-110
    Description: 3.4. Geomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: Geomagnetic field ; Ergodicity ; Chaos ; Geomagnetic field prediction ; 04. Solid Earth::04.05. Geomagnetism::04.05.01. Dynamo theory ; 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
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    Repeat-station surveys: implications from chaos and ergodicity of the recent geomagnetic field (2013)
    INGV
    Details
    Publication Date: 2017-04-04
    Description: The present geomagnetic field is chaotic and ergodic: chaotic because it can no longer be predicted beyond around 6 years; and ergodic in the sense that time averages correspond to phase-space averages. These properties have already been deduced from complex analyses of observatory time series in a reconstructed phase space [Barraclough and De Santis 1997] and from global predicted and definitive models of differences in the time domain [De Santis et al. 2011]. These results imply that there is a strong necessity to make repeat-station magnetic surveys more frequently than every 5 years. This, in turn, will also improve the geomagnetic field secular variation models. This report provides practical examples and case studies.
    Description: Published
    Description: R0103
    Description: 3.4. Geomagnetismo
    Description: JCR Journal
    Description: open
    Keywords: Geomagnetic field ; Repeat Stations ; Ergodicity ; Chaos ; 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::04.05.08. Instruments and techniques ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis ; 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
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    A note on two expressions for the spatial power spectrum of the geomagnetic field (2006)
    Details
    Publication Date: 2019-11-04
    Description: The spatial power spectrum of the geomagnetic field is usually assumed to be exponential in the spherical harmonic degree (n). An equally valid assumption, however, is that the spectrum at the surface of the Earth's core has a power-law dependence on n. Some implications of these two assumptions are discussed, noting that, in the first case, a value for the core radius can be derived from the slope of the spectrum and, in the second, that the spectrum for radii greater than the radius of the core is a mixture of the exponential and power-law types.
    Description: JCR Journal
    Description: open
    Keywords: Geomagnetic field ; spatial power spectrum ; 04. Solid Earth::04.05. Geomagnetism::04.05.99. General or miscellaneous ; 05. General::05.09. Miscellaneous::05.09.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 734319 bytes
    Format: application/pdf
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  • 6
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    Repeat Station Activities (2011)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: A repeat station is a site whose position is AQ1 accurately known and where accurate measurements of the geomagnetic field vector are made at regular intervals in order to provide information about the secular variation of the geomagnetic field. In this chapter we begin by giving a brief history of the development of repeat station networks. We then describe the instruments used to make measurements at a repeat station. These include fixing the position of the station, finding the direction of true north and measuring the components of the geomagnetic field. Emphasis is given to techniques and instruments that are in current use. We next discuss the procedures that are used to reduce the measurements to a usable form and consider the uses to which the reduced data are put. Finally, we discuss the continued importance of such data in the present era of satellite geomagnetic surveys.
    Description: Submitted
    Description: In press
    Description: 1.6. Osservazioni di geomagnetismo
    Description: restricted
    Keywords: Geomagnetic field ; Repeat Stations ; Geomagnetic measurements ; 04. Solid Earth::04.02. Exploration geophysics::04.02.04. Magnetic and electrical methods ; 04. Solid Earth::04.05. Geomagnetism::04.05.08. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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