Person: Osete López, María Luisa
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First Name
María Luisa
Last Name
Osete López
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física de la Tierra y Astrofísica
Area
Física de la Tierra
Identifiers
36 results
Search Results
Now showing 1 - 10 of 36
Item Eccentric Dipole Evolution during the Last Reversal, Last Excursions, and Holocene Anomalies. Interpretation Using a 360-Dipole Ring Model(Geosciences, 2021) González López, Alicia; Osete López, María Luisa; Arquero Campuzano, Saioa; Molina Cardín, Alberto; Rivera Pérez, Pablo; Pavón Carrasco, Francisco JavierThe eccentric dipole (ED) is the next approach of the geomagnetic field after the generally used geocentric dipole. Here, we analyzed the evolution of the ED during extreme events, such as the Matuyama-Brunhes polarity transition (~780 ka), the Laschamp (~41 ka) and Mono Lake (~34 ka) excursions, and during the time of two anomalous features of the geomagnetic field observed during the Holocene: the Levantine Iron Age Anomaly (LIAA, ~1000 BC) and the South Atlantic Anomaly (SAA, analyzed from ~700 AD to present day). The analysis was carried out using the paleoreconstructions that cover the time of the mentioned events (IMMAB4, IMOLEe, LSMOD.2, SHAWQ-Iron Age, and SHAWQ2k). We found that the ED moves around the meridian plane of 0–180◦ during the reversal and the excursions; it moves towards the region of the LIAA; and it moves away from the SAA. To investigate what information can be extracted from its evolution, we designed a simple model based on 360-point dipoles evenly distributed in a ring close to the inner core boundary that can be reversed and their magnitude changed. We tried to reproduce with our simple model the observed evolution of the ED, and the total field energy at the Earth’s surface. We observed that the modeled ED moves away from the region where we set the dipoles to reverse. If we consider that the ring dipoles could be related to convective columns in the outer core of the Earth, our simple model would indicate the potential of the displacement of the ED to give information about the regions in the outer core where changes start for polarity transitions and for the generation of important anomalies of the geomagnetic field. According to our simple model, the regions in which the most important events of the Holocene occur, or in which the last polarity reversal or excursion begin, are related to the regions of the Core Mantle Boundary (CMB), where the heat flux is low.Item Epsilon iron oxide: Origin of the high coercivity stable low Curie temperature magnetic phase found in heated archeological materials(Geochemistry geophysics geosystems, 2017) López Sánchez, Jesús; McIntosh, G.; Osete López, María Luisa; Campo García, A. del; Villalain, J.J.; Pérez García, Lucas; Kovacheva, M.; Rodríguez de la Fuente, ÓscarThe identification of epsilon iron oxide (-Fe2O3) as the low Curie temperature high coercivity stable phase (HCSLT) carrying the remanence in heated archeological samples has been achieved in samples from two archeological sites that exhibited the clearest evidence of the presence of the HCSLT. This uncommon iron oxide has been detected by Confocal Raman Spectroscopy (CRS) and characterized by rock magnetic measurements. Large numbers of -Fe2O3 microaggregates (in CO) or isolated clusters (in HEL) could be recognized, distributed over the whole sample, and embedded within the ceramic matrix, along with hematite and pseudobrookite and with minor amounts of anatase, rutile, and maghemite. Curie temperature estimates of around 170 degrees C for CO and 190 degrees C for HEL are lower than for pure, synthetic -Fe2O3 (227 degrees C). This, together with structural differences between the Raman spectra of the archeologically derived and synthetic samples, is likely due to Ti substitution in the -Fe2O3 crystal lattice. The -Fe2O3--Fe2O3--Fe2O3 transformation series has been recognized in heated archeological samples, which may have implications in terms of their thermal history and in the factors that govern the formation of -Fe2O3.Item Rapid Intensity Decrease During the Second Half of the First Millennium BCE in Central Asia and Global Implications(Journal of Geophysical Research: Solid Earth, 2021) Bonilla Alba, Raquel; Gómez Paccard, M.; Pavón Carrasco, Francisco Javier; del Rio, J.; Beamud, E.; Martínez Ferreras, V.; Gurt Esparraguera, J. M.; Arino Gil, E.; Palencia Ortas, A.; Martín Hernández, Fátima; Chauvin, A.; Osete López, María LuisaRecent paleomagnetic studies have shown that important short-lived intensity fluctuations occurred during the first millennium BCE. However, the knowledge of the spatial and temporal extension of these features is still limited by the scarce availability of robust data. In this study we focus on the study of the intensity decrease that took place in Central Asia during the second half of the 1st millennium BCE after the high intensities that characterized the Levantine Iron Age Anomaly. Since previous archeointensities available for this period and region were obtained without accomplishing modern standards of quality, we present here new archeointensities that are derived from classical Thellier and Thellier experiments, including partial thermoremanent magnetization (pTRM) checks, thermoremanent magnetization (TRM) anisotropy and cooling rate corrections at the specimen level. The new 51 archeointensities, together with previous archeointensities, have been used to present a new local paleosecular variation curve for Central Asia. The results confirm the existence of an important geomagnetic field intensity decrease in South Uzbekistan from the 4th century BCE to the end of the 1st century BCE associated with rates of changes up to -15 mu T/century. A critical analysis of the archeointensity global database indicates that this feature was present at continental scale, from Western Europe to Central Asia. However, this trend is not identified in other regions such as Japan or Mexico. Finally, the comparison with the dipole moment derived from recent global geomagnetic field reconstructions suggests a strong influence of non-dipolar sources upon this continental intensity feature.Item Propiedades magnéticas de sedimentos del Triásico Medio- Jurásico Inferior de la Cordillera Ibérica Occidental(Geotemas, 2000) Ruíz Martínez, Vicente Carlos; Osete López, María Luisa; Sopeña Ortega, AlfonsoA rock magnetic and palaeomagnetic study on two Middle-Late Triassic sections in the westernmost margin of the Iberian Ranges -that mostly consist of a thick sequence of interbedded mudstones and sandstones- and their Lower Jurassic top -dolomitized limestones- has been performed. Anisotropy of magnetic susceptibility thermomagnetic curves and hysteresis properties have been measured and the palaeomagnetic directions interpreted according to these analyses. Whereas the magnetic signal of the dolomitized Lower Jurassic limestone and some of the Triassic beds is unstable, multicomponent magnetisation behaviour has been observed in theTriassic red beds. The characteristic component presents high coercitivity and distributed unblocking temperatures up to 700-C (carried by hematite), showing both polarities and defining a consistent magnetic zonation. The NRM also contains lower unblocking temperature components with normal polarities. These are interpreted as result of the overlapping of a present day field component and an older overprint, probably related to the extensional phases of the Iberian Basin during the Cretaceous time. Primary remanence is better preserved in the fine-grained beds, showing a lower overlapping degree between the characteristic component and the high temperature overprint.Item Author correction: multi-centennial fluctuations of radionuclide production rates are modulated by the Earth's magnetic field (vol 8, 9820, 2018)(Scientific reports, 2019) Pavón Carrasco, Francisco Javier; Gómez Paccard, Miriam; Campuzano, S.A.; González Rouco, J. Fidel; Osete López, María LuisaTis Article contains errors in the Discussion section.Item Non-dipole and regional effects on the geomagnetic dipole moment estimation(Pure and Applied Geophys, 2015) Arquero Campuzano, Saioa; Pavón Carrasco, Francisco Javier; Osete López, María LuisaThe 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.Item New perspectives in the study of the Earth's magnetic field and climate connection: the use of transfer entropy(PLOS one, 2018) Pavón Carrasco, Francisco Javier; Osete López, María Luisa; Arquero Campuzano, Saioa; De Santis, Angelo; Qamili, EnkelejdaThe debated question on the possible relation between the Earth's magnetic field and climate has been usually focused on direct correlations between different time series representing both systems. However, the physical mechanism able to potentially explain this connection is still an open issue. Finding hints about how this connection could work would suppose an important advance in the search of an adequate physical mechanism. Here, we propose an innovative information-theoretic tool, i.e. the transfer entropy, as a good candidate for this scope because is able to determine, not simply the possible existence of a connection, but even the direction in which the link is produced. We have applied this new methodology to two real time series, the South Atlantic Anomaly (SAA) area extent at the Earth's surface (representing the geomagnetic field system) and the Global Sea Level (GSL) rise (for the climate system) for the last 300 years, to measure the possible information flow and sense between them. This connection was previously suggested considering only the long-term trend while now we study this possibility also in shorter scales. The new results seem to support this hypothesis, with more information transferred from the SAA to the GSL time series, with about 90% of confidence level. This result provides new clues on the existence of a link between the geomagnetic field and the Earth's climate in the past and on the physical mechanism involved because, thanks to the application of the transfer entropy, we have determined that the sense of the connection seems to go from the system that produces geomagnetic field to the climate system. Of course, the connection does not mean that the geomagnetic field is fully responsible for the climate changes, rather that it is an important driving component to the variations of the climate.Item Multi-centennial fluctuations of radionuclide production rates are modulated by the Earth's magnetic field(Scientific reports, 2018) Pavón Carrasco, Francisco Javier; Gómez Paccard, M.; Arquero Campuzano, Saioa; González Rouco, Jesús Fidel; Osete López, María LuisaThe production of cosmogenic isotopes offers a unique way to reconstruct solar activity during the Holocene. It is influenced by both the solar and Earth magnetic fields and thus their combined effect needs to be disentangled to infer past solar irradiance. Nowadays, it is assumed that the long-term variations of cosmogenic production are modulated by the geomagnetic field and that the solar field dominates over shorter wavelengths. In this process, the effects of the non-dipolar terms of the geomagnetic field are considered negligible. Here we analyse these assumptions and demonstrate that, for a constant solar modulation potential, the geomagnetic field exerts a strong modulation of multi-centennial to millennial wavelengths (periods of 800 and 2200 yr). Moreover, we demonstrate that the non-dipole terms derived from the harmonic degree 3 and above produce maximum differences of 7% in the global average radiocarbon production rate. The results are supported by the identification, for the first time, of a robust coherence between the production rates independently estimated from geomagnetic reconstructions and that inferred from natural archives. This implies the need to review past solar forcing reconstructions, with important implications both for the assessment of solar-climate relationships as well as for the present and future generation of paleoclimate models.Item Further progress in the study of epsilon iron oxide in archaeological baked clays(Physics of the Earth and Planetary Interiors, 2020) López Sánchez, J.; Palencia Ortas, A.; Campo, A. del; Mclntosh, G.; Kovacheva, M.; Martín Hernández, Fátima; Carmona, N.; Rodríguez de la Fuente, O.; Martín, P.; Molina Cardín, Alberto; Osete López, María LuisaThe occurrence of ε-Fe_(2)O_(3) in archaeological samples that have been subjected to high temperatures is gradually being detected by the use of micrometric structural characterization techniques. This work provides new information by revealing that the ε-Fe_(2)O_(3) is formed as a response to temperature, the aggregation state and the position within the baked clay with respect to the nearest heat source. In addition, depending mainly on the atmospheric environment, the temperature reached by the combustion structure, the distance from the heating source and the particle aggregation, other iron oxide magnetic phases are produced. In the baked clay studied here, hematite is found over the whole range of samples studied but its magnetic contribution is negligible. Magnetite is observed at the sample surface, probably due to local atmospheric environment closest to the combustion source. Maghemite is found at all depths up to 6 cm below the sample surface. ε-Fe_(2)O_(3) has a limited distribution, found within 2-3 cm of the sample surface. Furthermore, the viability of this compound as a palaeofield marker has been evaluated in both archaeological and synthetic samples. The results indicate that ε-Fe_(2)O_(3) is able to register the direction of the magnetic field. Linear palaeointensity plots have been obtained in synthetic samples, although the value of the palaeofield could be, sometimes, overestimated.Item Characteristic periods of the paleosecular variation of the Earth's magnetic field during the Holocene from global paleoreconstructions(Physics of the earth and planetary interiors, 2021) González López, Alicia; Arquero Campuzano, Saioa; Molina Cardín, Alberto; Pavón Carrasco, Francisco Javier; De Santis, A.; Osete López, María LuisaThe knowledge of the secular variation of the geomagnetic field at different time scales is important to determine the mechanisms that maintain the geomagnetic field and can help to establish constraints in dynamo theories. We have focused our study on the secular variation at millennial and centennial time scale searching for characteristic periods during the last 10 kyr. The frequency study was performed using four recent updated global paleomagnetic field reconstructions (SHA.DIF.14k, CALS10k.2, BIGMUDI4k and SHAWQ2k) by applying three techniques commonly used in signal analysis: the Fourier transform, the Empirical Mode Decomposition, and the wavelet analysis. Short-term variability of the geomagnetic field energy shows recurrent periods of around 2000, 1000–1400, and 600–800 and 250–400 years. The characteristic time around 600–800 years is well determined in all paleomagnetic reconstructions and it is mostly related to the axial dipole and axial octupole terms, but also observable in the equatorial dipole. In addition to this period, longer characteristic times of around 1000–1400 years are found particularly in the equatorial dipole and quadrupole terms in SHA.DIF.14k, CALS10k.2 and BIGMUDI4k while the 2000 year period is only well determined in the total geomagnetic field energy of SHA. DIF.14k and CALS10k.2. The most detailed paleoreconstructions for younger times also detect shortest characteristic times of around 250–400 years. The long-term variation of the geomagnetic energy is only observable in the axial dipole. A characteristic period of around 7000 years in both SHA.DIF.14k and CALS10k.2 has been found. This long period is related to two decays in the dipole field and a period of increasing intensity. The oldest decay took place between 7000 BCE and 4500 BCE and the present decay that started around 100 BCE. We have modeled the 4500 BCE up to present variation as a combination of a continuous decay, representing the diffusion term of the geomagnetic field, and one pulse that reinforces the strength of the field. Results show a characteristic diffusion time of around 11,000–15,000 years, which is compatible with the diffusion times of the dipole field used in geodynamo theories.