Pub Date : 2024-12-30Epub Date: 2024-12-24DOI: 10.1098/rsta.2023.0346
Adrià Labay-Mora, Jorge García-Beni, Gian Luca Giorgi, Miguel C Soriano, Roberta Zambrini
Quantum optical networks are instrumental in addressing the fundamental questions and enable applications ranging from communication to computation and, more recently, machine learning (ML). In particular, photonic artificial neural networks (ANNs) offer the opportunity to exploit the advantages of both classical and quantum optics. Photonic neuro-inspired computation and ML have been successfully demonstrated in classical settings, while quantum optical networks have triggered breakthrough applications such as teleportation, quantum key distribution and quantum computing. We present a perspective on the state of the art in quantum optical ML and the potential advantages of ANNs in circuit designs and beyond, in more general, analogue settings characterized by recurrent and coherent complex interactions. We consider two analogue neuro-inspired applications, namely quantum reservoir computing and quantum associative memories, and discuss the enhanced capabilities offered by quantum substrates, highlighting the specific role of light squeezing in this context.This article is part of the theme issue 'The quantum theory of light'.
{"title":"Neural networks with quantum states of light.","authors":"Adrià Labay-Mora, Jorge García-Beni, Gian Luca Giorgi, Miguel C Soriano, Roberta Zambrini","doi":"10.1098/rsta.2023.0346","DOIUrl":"https://doi.org/10.1098/rsta.2023.0346","url":null,"abstract":"<p><p>Quantum optical networks are instrumental in addressing the fundamental questions and enable applications ranging from communication to computation and, more recently, machine learning (ML). In particular, photonic artificial neural networks (ANNs) offer the opportunity to exploit the advantages of both classical and quantum optics. Photonic neuro-inspired computation and ML have been successfully demonstrated in classical settings, while quantum optical networks have triggered breakthrough applications such as teleportation, quantum key distribution and quantum computing. We present a perspective on the state of the art in quantum optical ML and the potential advantages of ANNs in circuit designs and beyond, in more general, analogue settings characterized by recurrent and coherent complex interactions. We consider two analogue neuro-inspired applications, namely quantum reservoir computing and quantum associative memories, and discuss the enhanced capabilities offered by quantum substrates, highlighting the specific role of light squeezing in this context.This article is part of the theme issue 'The quantum theory of light'.</p>","PeriodicalId":19879,"journal":{"name":"Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences","volume":"382 2287","pages":"20230346"},"PeriodicalIF":4.3,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142882734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-30Epub Date: 2024-12-24DOI: 10.1098/rsta.2023.0327
Miles Padgett
In 1992, Allen et al. (Allen L, Beijersbergen MW, Spreeuw RJC, Woerdman JP. 1992 Orbital angular momentum of light and the transformation of Laguerre-Gaussian laser modes. Phys. Rev. A45, 8185-8189. (doi:10.1103/physreva.45.8185)) published their seminal paper on the orbital angular momentum of light, drawing together seemingly unrelated themes and ideas in optics. This breakthrough initiated a new area of optical science concerning the physics and applications of structured light beams. This orbital angular momentum is an important concept for both classical and quantum science, especially where the framing in terms of angular momentum demystifies some of the quantum properties of light. Loudon's own work (Loudon R. 2003 Theory of the forces exerted by Laguerre-Gaussian light beams on dielectrics. Phys. Rev. A68, 013806. (doi:10.1103/PhysRevA.68.013806)) in this area focused on the interactions between light and matter where the orbital angular momentum extended his studies from linear impulses to rotational torques.This article is part of the theme issue 'The quantum theory of light'.
1992年,Allen et al. (Allen L, Beijersbergen MW, Spreeuw RJC, Woerdman JP)。1992光的轨道角动量与拉盖尔-高斯激光模的变换。理论物理。Rev. A 45, 8185-8189。(doi:10.1103/physreva.45.8185)))发表了他们关于光的轨道角动量的开创性论文,将光学中看似无关的主题和思想结合在一起。这一突破开创了一个光学科学的新领域,涉及结构光束的物理和应用。轨道角动量对于经典科学和量子科学来说都是一个重要的概念,特别是在角动量的框架下,光的一些量子特性变得更加神秘。劳登(Loudon R. 2003)关于拉盖尔-高斯光束对电介质施加的力的理论。理论物理。Rev. A 68, 013806。(doi:10.1103/PhysRevA.68.013806)))在这个领域专注于光与物质之间的相互作用,其中轨道角动量将他的研究从线性脉冲扩展到旋转力矩。这篇文章是主题“光的量子理论”的一部分。
{"title":"Orbital angular momentum of single photons: revealing quantum fundamentals.","authors":"Miles Padgett","doi":"10.1098/rsta.2023.0327","DOIUrl":"10.1098/rsta.2023.0327","url":null,"abstract":"<p><p>In 1992, Allen <i>et al</i>. (Allen L, Beijersbergen MW, Spreeuw RJC, Woerdman JP. 1992 Orbital angular momentum of light and the transformation of Laguerre-Gaussian laser modes. <i>Phys. Rev. A</i> <b>45</b>, 8185-8189. (doi:10.1103/physreva.45.8185)) published their seminal paper on the orbital angular momentum of light, drawing together seemingly unrelated themes and ideas in optics. This breakthrough initiated a new area of optical science concerning the physics and applications of structured light beams. This orbital angular momentum is an important concept for both classical and quantum science, especially where the framing in terms of angular momentum demystifies some of the quantum properties of light. Loudon's own work (Loudon R. 2003 Theory of the forces exerted by Laguerre-Gaussian light beams on dielectrics. <i>Phys. Rev. A</i> <b>68</b>, 013806. (doi:10.1103/PhysRevA.68.013806)) in this area focused on the interactions between light and matter where the orbital angular momentum extended his studies from linear impulses to rotational torques.This article is part of the theme issue 'The quantum theory of light'.</p>","PeriodicalId":19879,"journal":{"name":"Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences","volume":"382 2287","pages":"20230327"},"PeriodicalIF":4.3,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11667590/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142882742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-23Epub Date: 2024-12-02DOI: 10.1098/rsta.2024.0087
Krishan K Khurana, Jiang Liu, Julie Castillo-Rogez, Corey Cochrane, Francis Nimmo, Louise M Prockter
Triton, the largest satellite of Neptune, is in a retrograde orbit and is likely a captured Kuiper Belt Object (KBO). Triton has a mean density of only 2.061 gm/cm3 and is therefore believed to have a 250-400 km thick hydrosphere. Triton is also one of the few planetary satellites to possess a thick ionosphere whose height-integrated Pedersen conductivity exceeds 104 S, complicating the sounding of Triton's subsurface using electromagnetic induction. Triton experiences a time-varying magnetic field dominated by two periods, one at 14.4 h, at the synodic rotation period of Neptune (from Neptune's tilted field) and one at 141 h, at the orbital period of Triton (from large inclination of Triton's orbit). We show that for most models of ionospheric conductivity, the 14.4 h wave creates a large response from the ionosphere itself and is unable to sound the putative ocean below. However, the 141 h wave penetrates the ionosphere easily and provides information on Triton's ocean. We introduce a technique that allows us to determine the complex magnetic moments generated at the two key periods from the magnetic data from a single flyby, allowing us to infer the presence of a subsurface ocean.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.
{"title":"Dual-frequency electromagnetic sounding of a Triton ocean from a single flyby.","authors":"Krishan K Khurana, Jiang Liu, Julie Castillo-Rogez, Corey Cochrane, Francis Nimmo, Louise M Prockter","doi":"10.1098/rsta.2024.0087","DOIUrl":"https://doi.org/10.1098/rsta.2024.0087","url":null,"abstract":"<p><p>Triton, the largest satellite of Neptune, is in a retrograde orbit and is likely a captured Kuiper Belt Object (KBO). Triton has a mean density of only 2.061 gm/cm<sup>3</sup> and is therefore believed to have a 250-400 km thick hydrosphere. Triton is also one of the few planetary satellites to possess a thick ionosphere whose height-integrated Pedersen conductivity exceeds 10<sup>4</sup> S, complicating the sounding of Triton's subsurface using electromagnetic induction. Triton experiences a time-varying magnetic field dominated by two periods, one at 14.4 h, at the synodic rotation period of Neptune (from Neptune's tilted field) and one at 141 h, at the orbital period of Triton (from large inclination of Triton's orbit). We show that for most models of ionospheric conductivity, the 14.4 h wave creates a large response from the ionosphere itself and is unable to sound the putative ocean below. However, the 141 h wave penetrates the ionosphere easily and provides information on Triton's ocean. We introduce a technique that allows us to determine the complex magnetic moments generated at the two key periods from the magnetic data from a single flyby, allowing us to infer the presence of a subsurface ocean.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.</p>","PeriodicalId":19879,"journal":{"name":"Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences","volume":"382 2286","pages":"20240087"},"PeriodicalIF":4.3,"publicationDate":"2024-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142771347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-23Epub Date: 2024-12-02DOI: 10.1098/rsta.2024.0078
Alexander Grayver, Christopher C Finlay, Nils Olsen
The tidal flow of seawater across the Earth's magnetic field induces electric currents and magnetic fields within the ocean and solid Earth. The amplitude and phase of the induced fields depend on the electrical properties of both seawater and the solid Earth, and thus can be used as proxies to study the seabed properties or potentially for monitoring long-term trends in the global ocean climatology. This article presents new global oceanic tidal magnetic field models and their uncertainties for four tidal constituents, including [Formula: see text] and even [Formula: see text], which was not reliably retrieved previously. Models are obtained through a robust least-squares analysis of magnetic field observations from the Swarm and CHAMP satellites using a specially designed data selection scheme. We compare the retrieved magnetic signals with several alternative models reported in the literature. Additionally, we validate them using a series of high-resolution global three-dimensional (3D) electromagnetic simulations and place constraints on the conductivity of the sub-oceanic mantle for all tidal constituents, revealing an excellent agreement between all tidal constituents and the oceanic upper mantle structure.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.
{"title":"Magnetic signals from oceanic tides: new satellite observations and applications.","authors":"Alexander Grayver, Christopher C Finlay, Nils Olsen","doi":"10.1098/rsta.2024.0078","DOIUrl":"https://doi.org/10.1098/rsta.2024.0078","url":null,"abstract":"<p><p>The tidal flow of seawater across the Earth's magnetic field induces electric currents and magnetic fields within the ocean and solid Earth. The amplitude and phase of the induced fields depend on the electrical properties of both seawater and the solid Earth, and thus can be used as proxies to study the seabed properties or potentially for monitoring long-term trends in the global ocean climatology. This article presents new global oceanic tidal magnetic field models and their uncertainties for four tidal constituents, including [Formula: see text] and even [Formula: see text], which was not reliably retrieved previously. Models are obtained through a robust least-squares analysis of magnetic field observations from the <i>Swarm</i> and CHAMP satellites using a specially designed data selection scheme. We compare the retrieved magnetic signals with several alternative models reported in the literature. Additionally, we validate them using a series of high-resolution global three-dimensional (3D) electromagnetic simulations and place constraints on the conductivity of the sub-oceanic mantle for all tidal constituents, revealing an excellent agreement between all tidal constituents and the oceanic upper mantle structure.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.</p>","PeriodicalId":19879,"journal":{"name":"Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences","volume":"382 2286","pages":"20240078"},"PeriodicalIF":4.3,"publicationDate":"2024-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142771412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-23Epub Date: 2024-12-02DOI: 10.1098/rsta.2024.0084
Takuto Minami
Electrically conductive seawater, moving in an ambient magnetic field, generates electromagnetic (EM) variations. Tsunamis are significant contributors to this phenomenon, inducing observable electric and magnetic fluctuations at seafloor and coastal observatories. While understanding of these occurrences in open oceans is robust, knowledge regarding their observation on islands remains limited. This article seeks, through the use of numerical experimentation, to enhance our understanding of tsunami-generated EM (TGEM) variations observed on islands. Utilizing simulations involving conical islands, we identify three key insights regarding EM intensity normalized by the height of incident tsunamis: (i) increased ocean depth surrounding the island amplifies tsunami EM signals, particularly for periods shorter than 20 min; (ii) magnetic field strength at the island is approximately comparable to that observed at the seafloor in the absence of the island when the island radius is smaller than 6 km; and (iii) electric field intensity at the island notably surpasses that observed at the seafloor, especially with smaller island radii ([Formula: see text] 6 km). Additionally, we establish that employing the ratio of island radius to tsunami wavelength near the island coast facilitates the derivation of empirical functions for this phenomenon.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.
{"title":"Properties of tsunami-generated electromagnetic variation observed on islands.","authors":"Takuto Minami","doi":"10.1098/rsta.2024.0084","DOIUrl":"https://doi.org/10.1098/rsta.2024.0084","url":null,"abstract":"<p><p>Electrically conductive seawater, moving in an ambient magnetic field, generates electromagnetic (EM) variations. Tsunamis are significant contributors to this phenomenon, inducing observable electric and magnetic fluctuations at seafloor and coastal observatories. While understanding of these occurrences in open oceans is robust, knowledge regarding their observation on islands remains limited. This article seeks, through the use of numerical experimentation, to enhance our understanding of tsunami-generated EM (TGEM) variations observed on islands. Utilizing simulations involving conical islands, we identify three key insights regarding EM intensity normalized by the height of incident tsunamis: (i) increased ocean depth surrounding the island amplifies tsunami EM signals, particularly for periods shorter than 20 min; (ii) magnetic field strength at the island is approximately comparable to that observed at the seafloor in the absence of the island when the island radius is smaller than 6 km; and (iii) electric field intensity at the island notably surpasses that observed at the seafloor, especially with smaller island radii ([Formula: see text] 6 km). Additionally, we establish that employing the ratio of island radius to tsunami wavelength near the island coast facilitates the derivation of empirical functions for this phenomenon.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.</p>","PeriodicalId":19879,"journal":{"name":"Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences","volume":"382 2286","pages":"20240084"},"PeriodicalIF":4.3,"publicationDate":"2024-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142770891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-23Epub Date: 2024-12-02DOI: 10.1098/rsta.2024.0088
Robert H Tyler, David S Trossman
Ocean tide generated magnetic fields contain information about changes in ocean heat content and transport that can potentially be retrieved from remotely sensed magnetic data. To provide an important baseline towards developing this potential, tidal signals are extracted from 288 land geomagnetic observatory records having observations within the 50-year time span 1965-2015. The extraction method uses robust iteratively reweighted least squares for a range of models using different predictant and predictor assumptions. The predictants are the time series of the three vector components at each observatory, with versional variations in data selection and processing. The predictors fall into two categories: one using time-harmonic bases and the other that directly use lunar and solar ephemerides with gravitational theory to describe the tidal forces. The ephemerides predictors are shown to perform better (fitting more variance with fewer predictors) than do the time-harmonic predictors, which include the traditional 'Chapman-Miller method'. In fitting the oceanic lunar tidal signals, the predictants with the highest signal/noise involve the 'vertical' magnetic vector component following principle-component rotation. The best simple semidiurnal predictor is the ephemeris series of lunar azimuth weighted by the inverse-cubed lunar distance. More variance is fitted with predictors representing the lunar tidal potential and gradients calculated for each location/time.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.
{"title":"Oceanic and ionospheric tidal magnetic fields extracted from global geomagnetic observatory data.","authors":"Robert H Tyler, David S Trossman","doi":"10.1098/rsta.2024.0088","DOIUrl":"https://doi.org/10.1098/rsta.2024.0088","url":null,"abstract":"<p><p>Ocean tide generated magnetic fields contain information about changes in ocean heat content and transport that can potentially be retrieved from remotely sensed magnetic data. To provide an important baseline towards developing this potential, tidal signals are extracted from 288 land geomagnetic observatory records having observations within the 50-year time span 1965-2015. The extraction method uses robust iteratively reweighted least squares for a range of models using different predictant and predictor assumptions. The predictants are the time series of the three vector components at each observatory, with versional variations in data selection and processing. The predictors fall into two categories: one using time-harmonic bases and the other that directly use lunar and solar ephemerides with gravitational theory to describe the tidal forces. The ephemerides predictors are shown to perform better (fitting more variance with fewer predictors) than do the time-harmonic predictors, which include the traditional 'Chapman-Miller method'. In fitting the oceanic lunar tidal signals, the predictants with the highest signal/noise involve the 'vertical' magnetic vector component following principle-component rotation. The best simple semidiurnal predictor is the ephemeris series of lunar azimuth weighted by the inverse-cubed lunar distance. More variance is fitted with predictors representing the lunar tidal potential and gradients calculated for each location/time.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.</p>","PeriodicalId":19879,"journal":{"name":"Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences","volume":"382 2286","pages":"20240088"},"PeriodicalIF":4.3,"publicationDate":"2024-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11608825/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142771417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-23Epub Date: 2024-12-02DOI: 10.1098/rsta.2024.0079
J Velímský, L Šachl
Electrical conductivity of the Earth's oceans is an important oceanographic parameter related through its dependence on temperature and salinity to the state of the ocean. The tidally induced magnetic field then provides a directly and globally observable physical variable affected by the ocean conductivity spatial and temporal distribution. This contribution addresses two topics of the impact of the ocean conductivity variations on the principal lunar semi-diurnal magnetic signals. First, using high-resolution forward modelling, we investigate the sensitivity of the magnetic field to seasonal conductivity variations. Here, we find that the differences between magnetic signatures calculated for individual monthly conductivity climatologies are small, and localized to the marginal seas of the global ocean. Second, we formulate an inverse method to provide a constraint for the ocean conductivity in the upper 1000 m of the ocean, and test it using a synthetic dataset, demonstrating a proof-of-concept for such an approach.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.
{"title":"Sensitivity of M<sub>2</sub> tidal magnetic signals to seasonal and spatial variations of ocean electric conductivity.","authors":"J Velímský, L Šachl","doi":"10.1098/rsta.2024.0079","DOIUrl":"https://doi.org/10.1098/rsta.2024.0079","url":null,"abstract":"<p><p>Electrical conductivity of the Earth's oceans is an important oceanographic parameter related through its dependence on temperature and salinity to the state of the ocean. The tidally induced magnetic field then provides a directly and globally observable physical variable affected by the ocean conductivity spatial and temporal distribution. This contribution addresses two topics of the impact of the ocean conductivity variations on the principal lunar semi-diurnal magnetic signals. First, using high-resolution forward modelling, we investigate the sensitivity of the magnetic field to seasonal conductivity variations. Here, we find that the differences between magnetic signatures calculated for individual monthly conductivity climatologies are small, and localized to the marginal seas of the global ocean. Second, we formulate an inverse method to provide a constraint for the ocean conductivity in the upper 1000 m of the ocean, and test it using a synthetic dataset, demonstrating a proof-of-concept for such an approach.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.</p>","PeriodicalId":19879,"journal":{"name":"Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences","volume":"382 2286","pages":"20240079"},"PeriodicalIF":4.3,"publicationDate":"2024-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142770979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ocean-bottom pressure gauges are widely used for tsunami observations due to their established accuracy and stability. Recent advancements reveal that the magnetic field fluctuates when a large tsunami passes over the ocean, suggesting potential alternatives to pressure gauges in the form of ocean-bottom electromagnetometers (OBEMs). This article offers a comprehensive synthesis of recent findings concerning tsunami magnetic fields and their utility in tsunami source estimation. In addition, we scrutinize the effectiveness of tsunami observations employing OBEMs. Despite the promise of electromagnetometers, it is worth noting that the background noise inherent in electromagnetic observations tends to be approximately 10 times greater than that of pressure observations within the critical tsunami frequency bands. The Earth's magnetic field sporadically disrupts tsunami magnetic fields, presenting a potential limitation to the utility of electromagnetometers in tsunami detection when compared with pressure gauges. Nevertheless, our investigation underscores the potential of electromagnetic observations in detecting tsunamis propagating over the ocean at magnitudes of a few centimetres. An invaluable advantage of electromagnetometers over pressure monitoring lies in their capability to observe tsunami velocity fields, suggesting a promising avenue for further research and development in tsunami observation technology.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.
{"title":"Harnessing electromagnetic data for tsunami source estimation: a comprehensive review.","authors":"Toshitaka Baba, Zhiheng Lin, Takuto Minami, Hiroaki Toh","doi":"10.1098/rsta.2024.0082","DOIUrl":"https://doi.org/10.1098/rsta.2024.0082","url":null,"abstract":"<p><p>Ocean-bottom pressure gauges are widely used for tsunami observations due to their established accuracy and stability. Recent advancements reveal that the magnetic field fluctuates when a large tsunami passes over the ocean, suggesting potential alternatives to pressure gauges in the form of ocean-bottom electromagnetometers (OBEMs). This article offers a comprehensive synthesis of recent findings concerning tsunami magnetic fields and their utility in tsunami source estimation. In addition, we scrutinize the effectiveness of tsunami observations employing OBEMs. Despite the promise of electromagnetometers, it is worth noting that the background noise inherent in electromagnetic observations tends to be approximately 10 times greater than that of pressure observations within the critical tsunami frequency bands. The Earth's magnetic field sporadically disrupts tsunami magnetic fields, presenting a potential limitation to the utility of electromagnetometers in tsunami detection when compared with pressure gauges. Nevertheless, our investigation underscores the potential of electromagnetic observations in detecting tsunamis propagating over the ocean at magnitudes of a few centimetres. An invaluable advantage of electromagnetometers over pressure monitoring lies in their capability to observe tsunami velocity fields, suggesting a promising avenue for further research and development in tsunami observation technology.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.</p>","PeriodicalId":19879,"journal":{"name":"Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences","volume":"382 2286","pages":"20240082"},"PeriodicalIF":4.3,"publicationDate":"2024-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11608826/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142771371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-23Epub Date: 2024-12-02DOI: 10.1098/rsta.2024.0077
Christopher C Finlay, Jakub Velímský, Clemens Kloss, Rasmus M Blangsbøll
Satellite magnetic field observations have the potential to provide valuable information on dynamics, heat content and salinity throughout the ocean. Here, we present the expected spatio-temporal characteristics of the ocean-induced magnetic field (OIMF) at satellite altitude on periods of months to decades. We compare these to the characteristics of other sources of Earth's magnetic field, and discuss whether it is feasible for the OIMF to be retrieved and routinely monitored from space. We focus on large length scales (spherical harmonic degrees up to 30) and periods from one month up to 5 years. To characterize the expected ocean signal, we make use of advanced numerical simulations taking high-resolution oceanographic inputs and solve the magnetic induction equation in three dimensions, including galvanic coupling and self-induction effects. We find the time-varying ocean-induced signal dominates over the primary source of the internal field, the core dynamo, at high spherical harmonic degree with the cross-over taking place at degrees 13-19 depending on the considered period. The ionospheric and magnetospheric fields (including their Earth-induced counterparts) have most power on periods shorter than one month and are expected to be mostly zonal in magnetic coordinates at satellite altitude. Based on these findings, we discuss future prospects for isolating and monitoring long period OIMF variations using data collected by present and upcoming magnetic survey satellites.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.
{"title":"Satellite monitoring of long period ocean-induced magnetic field variations.","authors":"Christopher C Finlay, Jakub Velímský, Clemens Kloss, Rasmus M Blangsbøll","doi":"10.1098/rsta.2024.0077","DOIUrl":"https://doi.org/10.1098/rsta.2024.0077","url":null,"abstract":"<p><p>Satellite magnetic field observations have the potential to provide valuable information on dynamics, heat content and salinity throughout the ocean. Here, we present the expected spatio-temporal characteristics of the ocean-induced magnetic field (OIMF) at satellite altitude on periods of months to decades. We compare these to the characteristics of other sources of Earth's magnetic field, and discuss whether it is feasible for the OIMF to be retrieved and routinely monitored from space. We focus on large length scales (spherical harmonic degrees up to 30) and periods from one month up to 5 years. To characterize the expected ocean signal, we make use of advanced numerical simulations taking high-resolution oceanographic inputs and solve the magnetic induction equation in three dimensions, including galvanic coupling and self-induction effects. We find the time-varying ocean-induced signal dominates over the primary source of the internal field, the core dynamo, at high spherical harmonic degree with the cross-over taking place at degrees 13-19 depending on the considered period. The ionospheric and magnetospheric fields (including their Earth-induced counterparts) have most power on periods shorter than one month and are expected to be mostly zonal in magnetic coordinates at satellite altitude. Based on these findings, we discuss future prospects for isolating and monitoring long period OIMF variations using data collected by present and upcoming magnetic survey satellites.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.</p>","PeriodicalId":19879,"journal":{"name":"Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences","volume":"382 2286","pages":"20240077"},"PeriodicalIF":4.3,"publicationDate":"2024-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11608848/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142770818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-23Epub Date: 2024-12-02DOI: 10.1098/rsta.2024.0089
Robert Tyler, Hiroaki Toh, Krishan Khurana, Ikuko Fujii
{"title":"Magnetometric remote sensing of Earth and planetary oceans.","authors":"Robert Tyler, Hiroaki Toh, Krishan Khurana, Ikuko Fujii","doi":"10.1098/rsta.2024.0089","DOIUrl":"https://doi.org/10.1098/rsta.2024.0089","url":null,"abstract":"","PeriodicalId":19879,"journal":{"name":"Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences","volume":"382 2286","pages":"20240089"},"PeriodicalIF":4.3,"publicationDate":"2024-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11608823/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142771415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}