Changes In Field Direction Research Articles

High performance few-mode fiber-based light field direction sensing system using deep convolutional neural network: fiber speckle demodulation network (FSDNET)

Precisely sensing the light field direction information plays the essential role in the fields of three-dimensional (3D) imaging, light field sensing, target positioning and tracking, remote sensing, etc. It is thrilling to find that the optical fiber can be used as a sensing component due to its high sensitivity, compact size, and strong resistance to electromagnetic interference. According to the core principle that the few-mode fiber output speckle pattern is sensitive to the change of incident light field direction, the variation characteristics is further investigated in this research study. Based on the simulation and analysis of the fiber transmission characteristics, the output speckle corresponding to the incident light field with the direction in the range of ±6° horizontally and vertically are calculated. Furthermore, a deep convolutional neural network (CNN): fiber speckle demodulation network (FSDNET) is proposed and constructed to establish what we believe to be a novel way to reveal and identify the mapping relationship between the light field direction and the output speckle. The theoretical simulation shows that the mean absolute error (MAE) between the perceived light field directions and the true directions is 0.01°. Then, a light field direction sensing system based on the few-mode fiber is developed. Regarding to the performance of the sensing system, the MAE of the FSDNET for the light field directions that have appeared in the training set is 0.0389°, and for testing set of the unknown directions that have not appeared in the training set, the MAE is 0.0570°. Therefore, the simulation and experimental results prove that high performance sensing of light field direction can be achieved by the proposed few-mode fiber sensing system and the FSDNET.

Magnetic field caused enhanced absorption and circular dichroism of an achiral plasmonic nanostructure.

In this paper, modulation of light-matter interactions by a magnetic field is used to generate circular dichroism (CD) from an achiral plasmonic nanostructure. Theoretical investigations show an increase in light absorption by the nanostructure in the presence of a magnetic field. The achiral nanostructure exhibits CD in external magnetic field parallel to circularly polarized light (CPL) incidence. The CD emergence is caused by modulation of electron motion to reduced/enhanced frequencies under CPL incidence. Compared to previous studies, in this paper the mechanism of CD emergence, and the physical reasoning behind the change in CD due to change in magnetic field direction and intensity, are explained. CD intensity increases with increasing magnetic field intensity, while CD sign changes on magnetic field direction reversal. Varying structural parameters significantly influences CD intensity. This study can be helpful in magneto-optics and in magneto-chiral applications.

NUMERICAL study of MAGNETO convective Buongiorno nanofluid flow in a rectangular enclosure under oblique magnetic field with heat generation/absorption and complex wall conditions

A mathematical model is presented to analyze the magnetohydrodynamic (MHD) convective flow in a rectangular enclosure. Earlier studies on the Tiwai-Das volume fraction nanofluid model did not consider the Buongiorno nanofluid model. This is the focus of the present analysis which examines the laminar mixed convection magnetohydrodynamic flow of a nanofluid in a differentially heated rectangular enclosure with complex boundary conditions under an inclined magnetic field. Buongiorno's two-component nanofluid model is employed, which incorporates the effects of Brownian motion and thermophoretic diffusion of nanoparticles. Magnetic nanofluids have considerable potential for enhancing transport processes in energy systems such as hybrid fuel cells. The study is essential with heat generation/absorption effects. Additionally, the work is highlighted by the general case of an oblique (inclined) magnetic field. The conservation equations for mass, primary and secondary momentum, energy, and nanoparticle concentration with wall boundary conditions are dimensionless using appropriate scaling transformations. A finite-difference computational scheme known as the Harlow-Welch Marker and Cell (MAC) method is employed to solve the dimensionless nonlinear coupled boundary value problem. A mesh independence study is included. Graphical plots are presented for the impact of key control parameters on streamline contours, isotherm contours, iso-concentration (nanoparticle mass) contours, and local Nusselt number. With heat sink (absorption), the Nusselt number is enhanced in magnitude whereas it is suppressed with heat generation since there is a heat reduction transmitted to the boundary. The configurations of streamlines, isotherms, and iso-concentrations are mostly invariant to magnetic field direction changes. The obtained results show interesting behaviors of the flow and thermal fields, which mainly involve the effect of Brownian motion and thermophoresis parameters, as well as unsteady regimes, depending on specific values of the Schmidt number, Richardson number, and Prandtl numbers. Increasing the Schmidt number induces a contraction in the central cooler zone in the enclosure and also reduces the iso-concentration magnitudes in the central region across the enclosure. The core region of the enclosure heats up as the thermophoresis and Brownian motion parameters rise, pushing the previously cooler top and bottom wall zones further away from the center. There is also a decrease in iso-concentration magnitudes in particular at the upper and lower boundaries at higher values of Brownian motion and thermophoresis parameters. At decreasing buoyancy ratios, the left vortex cell first decelerates while the right vortex cell accelerates. However, when the buoyancy ratio increases, the left vortex cell streamlines magnitudes increase with a contraction in vortex size, while the right cell develops. A Very minor alteration is observed in the isotherm and iso-concentration contours with an increasing buoyancy ratio. When the Richardson number increases, the vortex cell structures shift from a strong circulation cell on the left to a weaker cell on the right, resulting in reverse distribution. With the rising Richardson number, significant cooling is also caused in the core zone, as well as a drop in iso-concentrations, with the original dual low-concentration upper and lower zones merging into a single center zone. The original symmetric left and right vortex cells are gradually twisted diagonally towards the right wall as the magnetic field increases, yet the stronger right cell and the weaker left cell are maintained.

Study on partial discharge and charge accumulation characteristics of oil‐pressboard insulation under DC superimposed harmonic voltage

AbstractThe oil‐pressboard insulation on the valve side of the converter transformer withstands pulsating square wave voltage. The voltage contains lots of DC components and high‐order harmonics, which is likely to cause insulation failures. The partial discharge and space charge experiments of oil‐impregnated pressboard under DC superimposed harmonic voltage are conducted to study the effects of harmonic frequency and DC components on the discharge and charge accumulation and to explore the correlation mechanism of charge dynamic behaviour and discharge. Firstly, it is found that high‐order harmonic voltage promotes the partial discharge generation, but DC component suppresses the discharge. Moreover, the charge inside the pressboard is mainly injected in the same polarity and accumulates over time. The space charge density near the electrode increases with the increase of harmonic frequency, and the large amount of charge injection leads to electric field distortion. Meanwhile, the electric field direction changes faster, and the frequent charge injection and extraction behaviours make the charge recombination intensify, which promotes the discharge. Through the above analysis, the influence law of harmonic voltage on the failure of oil‐pressboard insulation is obtained, providing a theoretical basis for the structural optimisation and condition assessment of the converter transformer insulation.

Effect of terahertz electromagnetic field on single-file water transport through a carbon nanotube.

With the advancement in terahertz technology, the terahertz electromagnetic field has been proven to be an effective strategy to tune the nanofluidic transport. In this study, we utilize molecular dynamics simulations to systematically analyze the transport of single-file water through a carbon nanotube (CNT) under terahertz electromagnetic fields, focusing on the CNT length, field strength, polarization direction and frequency. Strikingly, with the increase in field strength, the water flow exhibits a transition from normal to super permeation states because of the resonance effect, and the threshold field shifts to low values for long CNTs. The field component parallel to the CNT axis contributes to the resonance effect and increasing water flow, but the vertical component maintains the structure of the single-file water chain and even impedes the water flow. As a result, for a continuous change of field direction, the water flow changes from super permeation to normal states. With the increase in field frequency, the water flow also changes from super permeation to normal or even frozen states, where a higher frequency is required to trigger the super permeation states for lower field strength. Our results provide a comprehensive insight into the effect of terahertz electromagnetic field on the transport of single-file water chains and should have great implications for designing novel nanofluidic devices.

Magnetoreceptory Function of European Robin Retina: Electrophysiological and Morphological Non-Homogeneity.

The avian magnetic compass allows orientation during migration and is shown to function properly under short-wavelength but not long-wavelength visible light. Therefore, the magnetoreceptive system is assumed to be light- and wavelength-dependent and localized in the retina of the eye. Putative candidates for the role of primary magnetosensory molecules are the cryptochromes that are known to be expressed in the avian retina and must be able to interact with phototransduction proteins. Previously, we reported that in migratory birds change in magnetic field direction induces significant effects on electroretinogram amplitude in response to blue flashes, and such an effect was observed only in the nasal quadrant of the retina. Here, we report new electroretinographic, microscopic and microspectrophotometric data on European robins, confirming the magnetosensitivity of the retinal nasal quadrant after applying the background illumination. We hypothesized that magnetoreceptive distinction of this region may be related to its morphology and analyzed the retinal distribution and optical properties of oil droplets, the filtering structures within cones. We found that the nasal quadrant contains double cones with the most intensely colorized oil droplets compared to the rest of the retina, which may be related to its magnetosensory function.

Hybrid Simulations of a Tangential Discontinuity‐Driven Foreshock Bubble Formation in Comparison With a Hot Flow Anomaly Formation

AbstractHot flow anomalies (HFAs) and foreshock bubbles (FBs) are significant foreshock transients that can accelerate particles and disturb the magnetosphere‐ionosphere system. Yet, their early formation mechanisms are still not fully understood. To investigate the formation of tangential discontinuity (TD)‐driven FBs and HFAs, we use 2‐D local hybrid simulations where a reflected or an injected warm foreshock ion beam can interact with a TD whose half‐thickness is comparable to the ion inertial scale. We show that the foreshock ions perform a partial gyration within, or across, the TD. Bulk motion differences between partially‐gyrating foreshock ions and fluid‐electrons lead to the generation of currents. As the trigger, these foreshock‐driven currents change the magnetic field topology around the TD and force the frozen‐in solar wind plasma to redistribute along with the field lines, shaping the foreshock transient. This confirms a recently proposed kinetic formation model. The extent of the magnetic field direction change across the TD within the foreshock ion gyromotion determines the current profile and thus the type of foreshock transient that forms. For a thin TD, the foreshock ions generate a current that is much stronger on the upstream side than the downstream side, forming an FB with one upstream compressional boundary. For the same foreshock ion gyroradius and magnetic shear, a thick TD yields comparable foreshock‐driven currents on the upstream and downstream sides, forming an HFA with two compressional boundaries. Our study suggests that the TD thickness is one of the factors that determine the formation of FBs and HFAs.

A Foreshock Bubble Driven by an IMF Tangential Discontinuity: 3D Global Hybrid Simulation

AbstractForeshock bubbles (FBs) have been observed upstream of solar wind tangential discontinuities (TDs). A hypothesized mechanism is that foreshock ions with gyroradii larger than the TD thickness may move to upstream side of TDs and generate FBs. In this study, we present the very first three‐dimensional global hybrid simulation of an FB driven by a TD. After the TD encounters the ion foreshock, plasma and magnetic field perturbations are generated upstream of the TD. These perturbations are characteristically consistent with the observed TD‐driven FBs, confirming that TDs can form FBs. We further analyze the initial perpendicular temperature increase initiating the FB and compare the temperature structure with that from tracing test‐particles in static TD electric and magnetic fields. The structure can be explained by the perpendicular velocity change of foreshock ions with large gyroradii as they encounter the magnetic field direction change across the TD, which supports the hypothesized mechanism.

Magnetic Elastomer Sensor for Dynamic Torque and Speed Measurements

In this paper is proposed a dynamic torque, rotational speed, and shaft position sensor. It is built of magnetic elastomer coating directly applied over a rotating shaft. The sensor is used for precise measurements of changes in torque and speed, and it is usable at high rotational speeds, directly on the device shaft. The sensor is based on magnetic elastomer material deformation and the corresponding change in magnetic field amplitude and direction. The proposed sensor design is simple and can acquire reliable readings for a wide range of rotational speeds. Sensor design consists of the following: magnetic elastomer coating with nanoparticles, in which, elastomer is used for a sensing convertor; magneto-resistive linear field sensor; and microprocessor unit for calibration and control. Numerical and experimental test results are demonstrated and analyzed. Sensor implementation aims to meet magnetic mechatronic systems’ specific requirements.

Study of the possibility of suppressing the influence of changes in an external magnetic field direction on the relative frequency fluctuations of two rubidium atomic clocks

Study of the possibility of suppressing the influence of changes in an external magnetic field direction on the relative frequency fluctuations of two rubidium atomic clocks

Coronal-jet-producing Minifilament Eruptions as a Possible Source of Parker Solar Probe Switchbacks

Abstract The Parker Solar Probe (PSP) has observed copious rapid magnetic field direction changes in the near-Sun solar wind. These features have been called “switchbacks,” and their origin is a mystery. But their widespread nature suggests that they may be generated by a frequently occurring process in the Sun’s atmosphere. We examine the possibility that the switchbacks originate from coronal jets. Recent work suggests that many coronal jets result when photospheric magnetic flux cancels, and forms a small-scale “minifilament” flux rope that erupts and reconnects with coronal field. We argue that the reconnected erupting-minifilament flux rope can manifest as an outward propagating Alfvénic fluctuation that steepens into an increasingly compact disturbance as it moves through the solar wind. Using previous observed properties of coronal jets that connect to coronagraph-observed white-light jets (a.k.a. “narrow CMEs”), along with typical solar wind speed values, we expect the coronal-jet-produced disturbances to traverse near-perihelion PSP in ≲25 minutes, with a velocity of ∼400 km s−1. To consider further the plausibility of this idea, we show that a previously studied series of equatorial latitude coronal jets, originating from the periphery of an active region, generate white-light jets in the outer corona (seen in STEREO/COR2 coronagraph images; 2.5–15 R ⊙), and into the inner heliosphere (seen in Solar-Terrestrial Relations Observatory (STEREO)/Hi1 heliospheric imager images; 15–84 R ⊙). Thus it is tenable that disturbances put onto open coronal magnetic field lines by coronal-jet-producing erupting-minifilament flux ropes can propagate out to PSP space and appear as switchbacks.

Anomalous magnetoresistance in detwinned EuFe2As2**Project supported by the Fundamental Research Funds for the Central Universities, China (Grant No. 2014JJCB27).

The in-plane magnetotransport of detwinned EuFe2As2 single crystal has been investigated. In the antiferromagnetic phase of Eu2+ spins, very different magnetoresistance results are observed upon the change of the external magnetic field direction and the current direction. This could be attributed to the tunable orientation of the Eu2+ spins under magnetic field. Electron scattering by spin fluctuation, superzone boundary effect, and cyclotron motion of charge carriers are used to interpret the observed anomalous magnetoresistance which is measured by using a current along a direction. The remarkable features of magnetoresistance suggest that itinerant electrons strongly couple with the spin configuration of Eu2+, which has a huge influence on the transport properties of EuFe2As2.

Spin-wave excitation and critical angles in a hybrid photon-magnon-coupled system

We studied “strongly enhanced” excitations of magnetostatic spin-waves in a hybrid magnon-photon-coupled system consisting of an inverted split-ring resonator and an yttrium iron garnet film. The backward-volume magnetostatic wave, magnetostatic surface wave, forward-volume magnetostatic wave modes, as well as multiple mixed modes were observed according to the direction of externally applied magnetic fields with respect to the spin-wave propagation direction. From experimental measurements, we found that there exist certain characteristic angles, which is to say, critical angles (θc, ϕc), whereby the group velocity of the excited spin-wave modes reaches zero, along with a single ferromagnetic resonance peak. Furthermore, we analytically derived the critical angles as sinθc=(Heff/H){2−(1+μ0Ms/Heff)sin2ϕc}−1/2, where Heff is the effective magnetic-field strength, H the externally applied field strength, and μ0Ms is the saturation magnetization. This analytical form is in quantitative agreement with estimations from experimentally observed spin-wave modes. This work not only provides a better understanding of multiple-mode spin-wave excitations in given field directions with the help of photon-magnon coupling, but also offers better coupling controllability based on the change of the external magnetic field direction.

Dynamic field line draping at comet 67P/Churyumov-Gerasimenko during the Rosetta dayside excursion

Context. The Rosetta dayside excursion took place in September–October 2015 when comet 67P/Churyumov-Gerasimenko (67P/CG) was located at ~1.36 AU from the Sun after it had passed perihelion on 13 August 2015 at ~1.25 AU. At this time, the comet was near its most active period, and its interaction with the solar wind was expected to be at its most intense, with ion pickup and magnetic field line draping. The dayside excursion was planned to move through different regions that were expected upstream of the cometary nucleus, and to possibly detect the location of the bow shock. Aims. The goal of this study is to describe the dynamic field line draping that takes place around the comet and the plasma processes that are connected to this. Methods. The data from the full Rosetta Plasma Consortium (RPC) were used to investigate the interaction of solar wind and comet, starting from boxcar-averaged magnetic field data in order to suppress high-frequency noise in the data. Through calculating the cone and clock angle of the magnetic field, we determined the draping pattern of the magnetic field around the nucleus of the comet. Then we studied the particle data in relation to the variations that are observed in the magnetic field. Results. During the dayside excursion, the magnetic field cone angle changed several times, which means that the magnetic field direction changes from pointing sunward to anti-sunward. This is caused by the changing directions of the interplanetary magnetic field that is transported toward the comet. The cone-angle direction shows that mass-loading of the interplanetary magnetic field of the solar wind leads to dynamic draping. The ion velocity and the magnetic field strength are correlated because the unmagnetized ions are accelerated more (less) strongly by the increasing (decreasing) magnetic field strength. There is an indication of an anticorrelation between the electron density and the magnetic field strength, which might be caused by the magnetized electrons being mirrored out of the strong field regions. The Rosetta RPC has shown that (dynamic) draping also occurs as mildly active comets, as was found at highly active comets such as 1P/Halley and 21P/Giacobini-Zinner, but also that determining both dynamic and nested draping will require a combination of fast flybys and slow excursions for future missions.

Magnetosheath Reconnection Before Magnetopause Reconnection Driven by Interplanetary Tangential Discontinuity: A Three‐Dimensional Global Hybrid Simulation With Oblique Interplanetary Magnetic Field

AbstractTerrestrial dayside dynamics associated with a southward turning, oblique interplanetary magnetic field (IMF) carried by an interplanetary tangential discontinuity (TD) is investigated by performing a three‐dimensional global‐scale hybrid simulation systematically for cases in which the incoming solar wind TD possesses various magnetic field rotation angles ΔΦ = 90° to 180° and half widths w = 2di0 to w = 30di0, where di0 is the ion inertial length in the solar wind. Overall, the TD is compressed while being transmitted into the magnetosheath, with different compression processes downstream of the quasi‐parallel (Q‐||) and quasi‐perpendicular (Q‐⊥) shocks. It is found that magnetosheath reconnection may take place downstream of both the Q‐|| and Q‐⊥ shocks due to interaction of the directional TD with the bow shock and magnetopause, but the existence of magnetosheath reconnection depends on w and ΔΦ. Magnetosheath flux ropes are formed through three‐dimensional patchy reconnection in the thinned current sheet, with a longer rope lengths under a larger ΔΦ. There exists a dawn‐dusk asymmetry in the spatial extent of the flux ropes, which becomes more significant as ΔΦ decreases. When ΔΦ decreases to 90°, no reconnection flux ropes are found. Magnetopause reconnection is initiated when the magnetic fluxes with a southward turning IMF (on the sunward side) reach the magnetopause, and the magnetopause flux ropes can be mixed with the magnetosheath ones. Our simulation demonstrates that the effects of a southward turning of the IMF may not be a simple field direction change that leads to reconnection only at the magnetopause.

Observational Aspects of Magnetic Reconnection at the Earth’s Magnetosphere

Magnetic field reconnection has shown to be the dominant process in the solar wind-Earth’s magnetosphere interaction. It enables mass, momentum, and energy exchange between different plasma regimes, and it is regarded as an efficient plasma acceleration and heating mechanism. Reconnection has been observed to occur in laboratory plasmas, at planetary magnetospheres in our Solar System, and the Sun. In this work, we focus on analyzing the characteristics of magnetic reconnection at the Earth’s magnetosphere according to spaceborne observations in the vicinity of our planet. Firstly, the locations where magnetic field reconnection are expected to occur within the vast magnetospheric region are addressed, and is shown how they are influenced by changes in the interplanetary magnetic field direction. The main magnetic field and plasma signatures of magnetic reconnection are discussed from both theoretical and observational points of view. Spacecraft observations of ion inertial length scale reconnection are also presented.

Paleomagnetic direction and paleointensity variations during the Matuyama\u2013Brunhes polarity transition from a marine succession in the Chiba composite section of the Boso Peninsula, central Japan

The youngest geomagnetic polarity reversal, the Matuyama–Brunhes (M–B) boundary, provides an important plane of data for sediments, ice cores, and lavas. The geomagnetic field intensity and directional changes that occurred during the reversal also provide important information for understanding the dynamics of the Earth’s outer core, which generates the magnetic field. However, the reversal process is relatively rapid in terms of the geological timescale; therefore, adequate temporal resolution of the geomagnetic field record is essential for addressing these topics. Here, we report a new high-resolution paleomagnetic record from a continuous marine succession in the Chiba composite section of the Kokumoto Formation of the Kazusa Group, Japan, that reveals detailed behaviors of the virtual geomagnetic poles (VGPs) and relative paleointensity changes during the M–B polarity transition. The resultant relative paleointensity and VGP records show a significant paleointensity minimum near the M–B boundary, which is accompanied by a clear “polarity switch.” A newly obtained high-resolution oxygen isotope chronology for the Chiba composite section indicates that the M–B boundary is located in the middle of marine isotope stage (MIS) 19 and yields an age of 771.7 ka for the boundary. This age is consistent with those based on the latest astronomically tuned marine and ice core records and with the recalculated age of 770.9 ± 7.3 ka deduced from the U–Pb zircon age of the Byk-E tephra. To the best of our knowledge, our new paleomagnetic data represent one of the most detailed records on this geomagnetic field reversal that has thus far been obtained from marine sediments and will therefore be key for understanding the dynamics of the geomagnetic dynamo and for calibrating the geological timescale.Graphical abstract.

Field ionization of Rydberg atoms in a single-cycle pulse

We study the ionization of Rydberg atoms in a single-cycle-pulse electric field based on both classical and quantum calculations. The ionization-probability curve exhibits a “ripple” structure as a function of the pulse duration and the field amplitude. These ripple structures are found to be dependent on the angular distribution of the initial state. A large electron-emission asymmetry is observed, and the ionized electron is almost completely emittedtoonesideoftheatomexceptwhenthepulselengthisroughlyoneRydbergperiod.Inboththelong-pulse and the short-pulse regimes, larger electron energy can be expected from the ionization of lower-lying Rydberg states, matching the observation in a recent experiment [S. Li and R. R. Jones, Phys. Rev. Lett. 112, 143006 (2014)]. This trend is closely related to the electron-emission asymmetry associated with the field-direction change in a single-cycle pulse. The possible implications of the different energy transfer in a single-cycle pulse from that in a multicycle pulse are also discussed briefly for the strong-field ionization of the ground atomic state.

Influence of Mo capping layer on magnetic anisotropy of MgO/CoFeB/Mo

In this paper, the influence of Mo capping layer on magnetic anisotropy of MgO/CoFeB/Mo with varying thickness is studied. It is found that Mo capping layer shows more saturated magnetic moments than Ta capping layer. The direction of the external magnetic field has a great influence on the magnetic anisotropy. The MgO/CoFeB/Mo sample prepared in an applied magnetic field parallel to the plane shows in-plane magnetic anisotropy (IMA). IMA becomes weak as the CoFeB thickness decreases, and it still exists when the thickness decreases to 1.1 nm. At the same time, the saturation field vertical to the plane decreases. When the thickness of CoFeB layer decreases to 0.9 nm or less, the IMA disappears. In our study, the saturated magnetization and magnetic dead layer are 1600 emu/cm3 and 0.26 nm at the annealing temperature 200 ℃, and the interface anisotropy is 0.91 erg/cm2, which is smaller than previous research results. Increasing the annealing temperature helps the sample keep the saturated state under a small magnetic field vertical to the plane, and makes IMA weak and transform into PMA. The variation of the Mo capping layer thickness affects the saturation magnetic moment of the sample. The magnetic moment shows a sharp downtrend when the Mo layer is between 1.2 and 1.6 nm, then it turns stabler with Mo capping layer thickening. Meanwhile, when the Mo capping layer is 1.6 nm, the external vertical saturation field becomes smallest. However under the parallel magnetic field, changing the thickness or annealing temperature, or changing both leads to no PMA occurring. When the magnetic field direction changes from parallel to vertical direction, some of the samples show PMA after the annealing process. The magnetic anisotropy of MgO/CoFeB/Mo varies with the thickness of Mo capping layer. IMA is present when the Mo capping layer is 1 nm or less while PMA is present when the Mo capping layer is between 1.2 and 5 nm. The sample coercive force in the vertical direction varies with thickness, and its magnetic hysteresis loss is much larger when the thickness of Mo capping layer is 1.4 nm.

Edward Irving FRSC CM. 27 May 1927 — 25 February 2014

Dr Edward (Ted) Irving, one of Canada's most respected geoscientists, died on 25 February 2014 in Saanichton, British Columbia, Canada, aged 86 years, leaving his wife, Sheila, children Katie, Susan, Martin and George, seven grandchildren and one great-grandchild. After his early work as a student at Cambridge, England, he moved first to Australia and then to Canada. Over more than 60 years his scientific career was devoted mainly to the use of magnetic remanence recorded in ancient rocks to address fundamental geological questions. This seemingly simple technology proved to have remarkably many applications. Through his measurements and analyses of rock samples that recorded the magnetic field at the time of their formation, Ted was in the forefront of demonstrating that continental drift was real, at a time when the theory was out of favour. His meticulous work on rocks from many areas of the world was instrumental in showing how continents have been constantly moving, breaking up and colliding to make new larger continents and then breaking up again. He published more than 200 articles in international scientific journals. His reference text Paleomagnetism and its applications to geological and geophysical problems is still widely used. Applying remanent magnetism to study the motion of continents, and to other important geological problems, required careful analyses and interpretations. These included showing that the secular change in the Earth's magnetic field direction averaged over time aligns with its rotation pole, that the Earth's magnetic field has reversed its polarity at irregular intervals of a few million years, and that overprinting by re-magnetizations of rocks at different geological times can be separated by special laboratory techniques. Other contributions included important research in ancient climates, continental glaciations, the origin of mountain systems, and the relative displacements of parts of continents (terranes), especially the inferred large northward movement of parts of western North America, a conclusion that remains controversial. His most important results depended critically on his developing and using the best field sampling methods, laboratory instrumentation and procedures, and methods of data analysis. During his career he established world-class palaeomagnetic laboratories in Cambridge and Canberra, and in Ottawa and Victoria in Canada. Ted Irving had broad interests and knowledge. He was a serious gardener and horticulturalist and wrote several scholarly articles on plants, especially on the biogeography of rhododendrons and magnolias. He received numerous awards and medals and wide recognition, including election as a Fellow of the Royal Society of London, a Fellow of the Royal Society of Canada, a Fellow of the American Geophysical Union, an Honorary Fellow of the Geological Society of London, and a Foreign Associate of the US National Academy of Sciences. He also received many awards and medals from professional geological societies. Ted Irving received honorary doctorates from three universities, and the Order of Canada, in recognition of his outstanding scientific contributions.