Earth's Magnetic Field Research Articles

Key gene networks that control magnetosome biomineralization in magnetotactic bacteria.

Magnetotactic bacteria (MTB) are a group of phylogenetically and morphologically diverse prokaryotes that have the capability of sensing Earth's magnetic field via nanocrystals of magnetic iron minerals. These crystals are enclosed within intracellular membranes or organelles known as magnetosomes and enable a sensing function known as magnetotaxis. Although MTB were discovered over half a century ago, the study of the magnetosome biogenesis and organization remains limited to a few cultured MTB strains. Here, we present an integrative genomic and phenomic analysis to investigate the genetic basis of magnetosome biomineralization in both cultured and uncultured strains from phylogenetically diverse MTB groups. The magnetosome gene contents/networks of strains are correlated with magnetic particle morphology and chain configuration. We propose a general model for gene networks that control/regulate magnetosome biogenesis and chain assembly in MTB systems.

The amphibian magnetic sense(s).

Sensitivity to the earth's magnetic field is the least understood of the major sensory systems, despite being virtually ubiquitous in animals and of widespread interest to investigators in a wide range of fields from behavioral ecology to quantum physics. Although research on the use of magnetic cues by migratory birds, fish, and sea turtles is more widely known, much of our current understanding of the functional properties of vertebrate magnetoreception has come from research on amphibians. Studies of amphibians established the presence of a light-dependent magnetic compass, a second non-light-dependent mechanism involving particles of magnetite and/or maghemite, and an interaction between these two magnetoreception mechanisms that underlies the "map" component of homing. Simulated magnetic displacement experiments demonstrated the use of a high-resolution magnetic map for short-range homing to breeding ponds requiring a sampling strategy to detect weak spatial gradients in the magnetic field despite daily temporal variation at least an order of magnitude greater. Overall, reliance on a magnetic map for short-range homing places greater demands on the underlying sensory detection, processing, and memory mechanisms than comparable mechanisms used by long-distance migrants. Moreover, unlike sea turtles and migratory birds, amphibians are exceptionally well suited to serve as model organisms in which to characterize the molecular and biophysical mechanisms underlying the light-dependent 'quantum compass'.

Magnetic Field and Agriculture Sustainability

Agriculture's sustainability depends on the need to use practices and technologies that are environmentally friendly and have no bad impact on the environment, are cost-effective and easily accessible to farmers, resulting in overall food productivity enhancement. Novel advanced techniques are required that integrate ecological and biological procedures to enhance food production and reduce the use of non-renewable resources, which are harmful to the environment and the health of individuals. The earth's magnetic field (MF) is one of the inevitable environmental factors affecting plant growth and yield. Because the MF technique is environmentally friendly, produces no waste, requires no power supply, and does not emit harmful radiation, it can be used for agricultural sustainability.

A Realistic Projection of Climate Change in the Upper Atmosphere Into the 21st Century

AbstractClimate change in the upper atmosphere (∼90–500 km altitude) has important impacts on practical applications. To prepare for these, realistic projections of future climate change are needed. The first climate projection up to 500 km altitude is presented here based on a long transient simulation with the whole atmosphere community climate model extension, following Shared Socio‐economic Pathway 2–4.5, a moderate emission scenario. Effects of predicted main magnetic field changes and reasonable solar radiative and particle forcings are also included. The predicted global mean cooling in the thermosphere and associated decline in thermosphere density for 2015–2070 are significantly stronger than for the historical period, which is ascribed to the more rapid increase in CO2 concentration. Trends in global mean ionospheric parameters also increase in magnitude, but there are considerable spatial variations, caused by changes in the Earth's magnetic field. The largest ionospheric changes are expected in the region of ∼50°S–20°N and ∼90–0°W.

Time-Periodic Spacecraft Attitude Control with the Use of Slewing Permanent Magnets

Introduction. Electromagnetic actuators are widely used in spacecraft (SC) attitude control systems. These actuators can be modified by using slewing permanent magnets (ASPM) as sources of torque instead of electromagnets. These modified devices consume less onboard electricity for SC attitude control than the conventional ones.Problem Statement. An algorithm for attitude stabilization of a SC using ASPM was proposed in previous studies, where the pole placement technique and pulse-width modulation (PWM) were used to design the controller. However, this approach does not allow the designers to find optimal values of the required magnetic torques, which may result in frequent engagement of the stepper motors of the ASPMs and their significant energy consumption. This controller has such a drawback because its gains are selected without taking into account time-periodic properties of the Earth magnetic field.Purpose. The purpose of the study is to design the algorithm for the SC angular stabilization by the ASPMs taking into account time-periodic properties of the Earth magnetic field.Materials and Methods. The solution of the time-periodic Riccati equation was used for the controller design. Mathematical modeling and computer simulation of SC motion was applied to build the model of the plan and validate the results.Results. A time-periodic based SC attitude control algorithm has been designed. Taking into consideration the time-periodic properties of the magnetic field of Earth allow us to optimize the required magnetic control torques. This algorithm minimizes the frequency of the actuation of the ASPM sashes, and thus reduces onboard energy consumption.Conclusions. The designed algorithm increases the control efficiency of SC attitude control by using jointly the ASPMs, time-periodic linear-quadratic regulator and pulse-width modulator.

Modeling a Three-Stage SQUID System in Space with the First Micro-X Sounding Rocket Flight

The Micro-X sounding rocket is a NASA funded X-ray telescope payload that completed its first flight on July 22, 2018. This event marked the first operation of Transition Edge Sensors (TESs) and their SQUID-based multiplexing readout system in space. Unfortunately, due to an ACS pointing failure, the rocket was spinning during its five minute observation period and no scientific data was collected. However, data collected from the internal calibration source marked a partial success for the payload and offers a unique opportunity to study the response of TESs and SQUIDs in space. Of particular interest is the magnetic field response of the NIST MUX06a SQUID readout system to tumbling through Earth's magnetic field. We present a model to explain the baseline response of the SQUIDs, which lead to a subset of pixels failing to "lock" for the full observational period. Future flights of the Micro-X rocket will include the NIST MUX18b SQUID system with dramatically reduced magnetic susceptibility.

Rapid Volcanic Modification of the E‐Region Dynamo: ICON's First Glimpse of the Tonga Eruption

AbstractThe 15 January 2022 Hunga Tonga‐Hunga Ha'apai volcano eruption drove global atmospheric waves that propagated into space and impacted the ionosphere. Here we show immediate large‐scale electrodynamic effects of the eruption using observations from the National Aeronautics and Space Administration's Ionospheric Connection Explorer. We report extreme zonal and vertical ion drifts thousands of kilometers away from Tonga within an hour of the eruption, before the arrival of any atmospheric wave. The measured drifts were magnetically connected to the ionospheric E‐region just 400 km from Tonga, suggesting that the expanding wavefront created strong electric potentials which were transmitted along Earth's magnetic field. A simple theoretical model suggests that the observed drifts are consistent with an expanding wave with a large (>200 m/s) neutral wind amplitude. These observations are the first direct detection in space of the immediate electrodynamic effects of a volcanic eruption and will help constrain future models of impulsive lower atmospheric events.

Late Holocene paleosecular variation and relative paleointensity records from Lagoa dos Patos (southern Brazil)

Lake and lagoon sediments are important recorders of the Earth's magnetic field variations. However, the Southern Hemisphere, particularly the South American continent, contributes only a small fraction of the global paleosecular variation (PSV) and relative paleointensity data, which hinders a better understanding of the global PSV. Moreover, the scarcity of information on the geomagnetic field in South Brazil for the past few millennia impedes, for example, a detailed analysis of the evolution of the South Atlantic Magnetic Anomaly (SAMA), which encompasses the weakest geomagnetic field on the Earth's surface. Here, we present high-resolution paleomagnetic and rock magnetic data of two cores collected at the lagoon of Lagoa dos Patos, Rio Grande do Sul State, Brazil. Sediment cores from Lagoa dos Patos represent the period from ∼4540 to 3320 cal years BP. Rock magnetic results show the remanent magnetization resides in pseudo single-domain (PSD) magnetite and/or titanomagnetite. Magnetization inclinations and declinations were isolated after alternating field demagnetization (AFD) and principal component analysis (PCA). Mean inclinations are −39,6° and − 38,4° for cores PT-04 and PT-06, respectively. Relative paleointensity results are compatible with geomagnetic field models, implying very promising results in the reconstruction of a reference curve for the region. As there is no PSV and relative paleointensity data for this region in this period, this study helps to elucidate the past field and the presence of SAMA in South America.

Seasonal and Diurnal Dynamics of Radio Noise for 8–20 MHz Poleward‐Oriented Mid‐Latitude Radars

AbstractBased on ray tracing in a smooth ionosphere described by the IRI‐2012 model we have inferred the seasonal‐diurnal dynamics of radio noise observed by four mid‐latitude high‐frequency (HF) radars. In the calculations, noise is assumed to be homogeneous and stationary, but the main contribution comes from the radar skip zone boundary due to focusing radiowaves effect. Noise absorption along the ray path is simulated from the IRI‐2012 electron density, and from the molecular nitrogen density and electron temperatures obtained from the NRLMSISE‐00 model. Earth magnetic field is not taken into account both in the absorption and ray‐tracing calculations due to insufficient accuracy of the ionospheric model. The model results are compared with experimental radar data, and good agreement between the two is demonstrated. It is shown that experimentally observed seasonal and diurnal dynamics of the noise correlates well with model predictions. We demonstrated saturation effect at low noise levels. The model makes it possible to estimate the amount of absorption in D‐ and E‐layers using noise observations at SuperDARN and SuperDARN‐like poleward‐oriented radars, especially at mid‐latitudes. This is important for the retrieval of long term variations in the electron density in the lower ionosphere, by using wide coverage provided by these radars' network. The model also makes it feasible to interpret vertical absorption by experimental noise observations, thereby significantly expanding the capability of HF radars to monitor the lower ionosphere, and to provide data for joint analysis with other data, obtained by these radars at E‐ and F‐layer heights.

Sulfur-isotope anomalies recorded in Antarctic ice cores as a potential proxy for tracing past ozone layer depletion events.

Changes in the cosmic-ray background of the Earth can impact the ozone layer. High-energy cosmic events [e.g. supernova (SN)] or rapid changes in the Earth's magnetic field [e.g. geomagnetic Excursion (GE)] can lead to a cascade of cosmic rays. Ensuing chemical reactions can then cause thinning/destruction of the ozone layer-leading to enhanced penetration of harmful ultraviolet (UV) radiation toward the Earth's surface. However, observational evidence for such UV "windows" is still lacking. Here, we conduct a pilot study and investigate this notion during two well-known events: the multiple SN event (≈10 kBP) and the Laschamp GE event (≈41 kBP). We hypothesize that ice-core-Δ33S records-originally used as volcanic fingerprints-can reveal UV-induced background-tropospheric-photochemical imprints during such events. Indeed, we find nonvolcanic S-isotopic anomalies (Δ33S ≠ 0‰) in background Antarctic ice-core sulfate during GE/SN periods, thereby confirming our hypothesis. This suggests that ice-core-Δ33S records can serve as a proxy for past ozone-layer-depletion events.

Magnetic fields produced by subsea high-voltage direct current cables reduce swimming activity of haddock larvae (Melanogrammus aeglefinus).

High-voltage direct current (HVDC) subsea cables are used to transport power between locations and from/to nearshore and offshore facilities. HVDC cables produce magnetic fields (B-fields) that could impact marine fish. Atlantic haddock (Melanogrammus aeglefinus) is a demersal fish that is at risk of exposure to anthropogenic B-fields. Their larvae drift over the continental shelf, and use the Earth's magnetic field for orientation during dispersal. Therefore, anthropogenic magnetic fields from HVDC cables could alter their behavior. We tested the behavior of 92 haddock larvae using a setup designed to simulate the scenario of larvae drifting past a B-field in the intensity range of that produced by a DC subsea cable. We exposed the larvae to a B-field intensity ranging from 50 to 150 µT in a raceway tank. Exposure to the B-field did not affect the spatial distribution of haddock larvae in the raceway. Larvae were categorized by differences in their exploratory behavior in the raceway. The majority (78%) of larvae were nonexploratory, and exposure to the artificial B-field reduced their median swimming speed by 60% and decreased their median acceleration by 38%. There was no effect on swimming of the smaller proportion (22%) of exploratory larvae. These observations support the conclusion that the swimming performance of nonexploratory haddock larvae would be reduced following exposure to B-field from HVDC cables. The selective impact on nonexploratory individuals, and the lack of impact on exploratory individuals, could have population-scale implications for haddock in the wild.

Regular Transitory Variations of the Horizontal Component of the Earth Magnetic Field in Democratic Republic of the Congo for one Solar Cycle

La République Démocratique du Congo, par rapport à sa position géographique, située au Sud de l'équateur géomagnétique, est une zone de grande variation de la composante horizontale du champ magnétique terrestre. Nous avons analysé le cycle solaire 1955-1965 pour les données des observatoires: Binza et Karavia pour mieux comprendre la variation de la composante horizontale du champ magnétique terrestre en tenant compte de cinq jours magnétiques calmes de chaque mois. De cette analyse, l'étude montre que la RDC est sous l'influence des courants de Hall et de Pedersen appelés courants ionosphériques horizontaux circulant dans l'ionosphère terrestre par rapport à l'équateur géomagnétique. Ces courants sont responsables de phénomènes magnétiques tels que les orages et les sous orages magnétiques dans l'atmosphère neutre et aussi de l'induction des courants dans la croûte terrestre responsable de forte variation de la composante horizontale du champ magnétique terrestre au sol. Ces effets se manifestent entre l'aube et le crépuscule, avec une intensité variable au cours de la journée. De ce qui précède, il est important de tenir compte de la variation de l'intensité des courants ionosphériques horizontaux d'une manière générale pour mieux protéger les réseaux électromagnétiques face aux inductions des courants dans la croûte terrestre et l'environnement terrestre contre les radiations solaires. Mots clés: Composante horizontale, courant ionosphérique, taches solaires

Design, simulation and fabrication of non-spiral based fluxgate sensor on printed circuit board (PCB)

This paper presents performance characteristics of non-spiral planar excitation and pick-up micro-coils implemented for a fluxgate sensor with a NiFe magnetic rod core.Using Ansys Maxwell's software, the sensor performance is simulated. Magnetic flux[ϕ], magnetic flux density [B], magnetic field intensity [H], coupling coefficient, inductance [L] and magnetic energy [E] of the coils are simulated for a set of excitation currents. A simple, cost-effective and less complex fabrication method is implemented to fabricate the sensor using Printed Circuit Board (PCB) technology. Non-spiral 5-turn fluxgate sensor of dimensions 50mmx 20mmx 0.5 mm [length × breadth × width] is fabricated and analysed at an excitation current with a fundamental frequency of 500 kHz. Two excitation coils and one pick-up coil are deposited on a horizontal PCB plane and NiFe rod type material is placed on it, which acts as the core. Synthetic glue is spread on the coils; it acts a insulator between the coils and the core. Copper is used for deposition of the both the excitation and pick-up coils. On applying different excitation current, the frequency response of the non-spiral fluxgate sensor is plotted. The sensor demonstrated earth magnetic field strength detection (∼25 μT).

New 40Ar/39Ar age of the full vector Upper Mammoth geomagnetic polarity transition recorded in the Pu’u Kualakauila volcanic sequence, Hawaii

Paleomagnetic measurements, coupled with 40Ar/39Ar dating, are improving our understanding of the geodynamo by providing detailed terrestrial lava records of the short-term behavior of the Earth's magnetic field. As part of an investigation of the Wai'anae Volcano, Oahu, and the short-term behavior of the geomagnetic field, we sampled a long volcanic section located on the volcano's collapsed flank at a locality known as Pu’u Kaulakauila. Prior paleomagnetic investigations of the Kamaile'unu Volcanic Series (i.e. Herrero-Bervera and Coe, 1999, Herrero-Bervera and Valet, 1999, 2005) revealed transitional directions. The fresh lava flows, easy access, and close geographical proximity to KAr dated flows made this ~215-m thick sequence of flows an excellent candidate for detailed paleomagnetic analysis. At least eight samples, collected from each of 47 successive flow sites, were stepwise demagnetized by both alternating field and thermal methods. Magnetostratigraphic results indicate the existence of four excursions or aborted reversals occurring at approximately ~36, ~75, ~130, and ~ 151 m above flow#1. The mean directions of magnetization of the entire section sampled indicate a reversed polarity, with ∼10 m of the section characterized by truly excursional/Cryptochron directions (~7 lava flows). Paleointensity (P.I.) determinations indicate a steady decreasing of the PI values from 75 μ-T to ~12.2 μ-T reaching a minimum of 7.1 μ-T. These very low PI values are within the transitional/excursional part of the record. The corresponding VGPs are located on the western part of Australia. 40Ar/39Ar incremental heating experiments on groundmass from transitional flow sites at different stratigraphic levels yield a weighted mean plateau age of 3.201 ± 0.041 Ma, which, combined with the overall reversed polarity and two older polarity reversals, strongly suggests that the transitional lavas correspond to the Upper Mammoth polarity transition.

Using Hill Climb Modular Assembler Encoding and Differential Evolution to evolve modular neuro-controllers of an autonomous underwater vehicle acting as a Magnetic Anomaly Detector

In order for any construction to arise on the sea bottom, the area around has to be carefully cleaned from all dangerous objects including ferromagnetic objects like ammunition or the remains of sea mines. Magnetic anomaly detectors (MAD) which are composed of a set of magnetometers are applied to detect such objects. The combined signal of all the magnetometers moving near the sea bottom is a base for detecting anomalies in the Earth magnetic field produced by ferromagnetic objects. To carry the magnetometers, underwater vehicles can be used. However, in order for the vehicles to be able to fulfill the role of MAD, they have to move near the sea bottom in a tight swarm formation. In the paper, a modular neuro-evolutionary controller is presented which leads each swarm member along a desired trajectory, with the time synchronization, and at the certain distance from the sea bottom. In order to design the controller, two neuro-evolutionary algorithms were applied, i.e. Hill Climb Modular Assembler Encoding (HCMAE) and Differential Evolution (DE). During tests carried out in simulation conditions, initially in 2D and then also in a 3D environment, under the influence of sea current, neuro-controllers evolved by HCMAE and DE were compared with algorithmic and PID-like controllers. The tests showed that the solutions proposed in the paper are more effective than the reference solutions and proved that even in unfavorable underwater conditions it is possible to precisely keep the trajectory specified both spatially and temporally.

High geomagnetic field intensity recorded by anorthosite xenoliths requires a strongly powered late Mesoproterozoic geodynamo

Obtaining estimates of Earth's magnetic field strength in deep time is complicated by nonideal rock magnetic behavior in many igneous rocks. In this study, we target anorthosite xenoliths that cooled and acquired their magnetization within ca. 1,092 Ma shallowly emplaced diabase intrusions of the North American Midcontinent Rift. In contrast to the diabase which fails to provide reliable paleointensity estimates, the anorthosite xenoliths are unusually high-fidelity recorders yielding high-quality, single-slope paleointensity results that are consistent at specimen and site levels. An average value of ∼83 ZAm2 for the virtual dipole moment from the anorthosite xenoliths, with the highest site-level values up to ∼129 ZAm2, is higher than that of the dipole component of Earth's magnetic field today and rivals the highest values in the paleointensity database. Such high intensities recorded by the anorthosite xenoliths require the existence of a strongly powered geodynamo at the time. Together with previous paleointensity data from other Midcontinent Rift rocks, these results indicate that a dynamo with strong power sources persisted for more than 14 My ca. 1.1 Ga. These data are inconsistent with there being a progressive monotonic decay of Earth's dynamo strength through the Proterozoic Eon and could challenge the hypothesis of a young inner core. The multiple observed paleointensity transitions from weak to strong in the Paleozoic and the Proterozoic present challenges in identifying the onset of inner core nucleation based on paleointensity records alone.

A high-fidelity high-efficiency model for electrodynamic tether system based on recursive algorithm

The electrodynamic tether (EDT) system is used as one of the end-of-life disposal technologies to deorbit defunct satellites with the benefit of Earth's magnetic field and plasma environment. However, due to the flexibility of the conductive tether, the orbit-attitude coupling effects as well as the influence of Multiphysics fields, this system suffers from time-consuming computations using complicated mathematical model in long-term simulations. Therefore, this paper proposes a high-fidelity high-efficiency dynamics model for the EDT system, in which the tether libration and transverse motions are described by the articulated model, and the system equations are formulated using recursive dynamics algorithm. Computational cost of the recursive method is compared with a nonrecursive method, and the result shows that with the number of tether elements larger than 15, the recursive method would show better computational efficiency. Since the conductive tether tends to be kilometers long in application, this new model would definitely contribute to the numerical efficiency. In addition, simulations are conducted with 2 and 16 tether elements solutions. By comparing the obtained results, it is found that the two cases show large differences over time. For a long tether, it is reasonable to use a larger number of elements in the dynamics analysis. Besides, in order to suppress the libration motion and avoid unstable states in the EDT system, a current control strategy is proposed and verified by a deorbit simulation in low Earth orbit.

A Small Peak in the Swarm‐LP Plasma Density Data at the Dayside Dip Equator

AbstractIn this paper, we statistically investigate an artifact in Langmuir Probe (LP) observations of Swarm satellites. A small peak of electron density (Ne) is frequently found in the Swarm data around the dayside dip equator. On the contrary, they appear in neither the Total Electron Content data of the Swarm/Global Positioning System Receivers nor COSMIC‐2 in‐situ measurements at similar altitudes but with low orbit inclination. Arguably, this peak does not represent natural ionospheric irregularities but is likely to result from artifacts. The phenomena are found regardless of the season, solar activity, and the velocity direction of the satellite (ascending and descending). They predominantly occur when the magnetic declination is close to zero, that is, when the Swarm ram direction and the Earth's magnetic field are aligned under sunlight. Hence, we attribute the phenomenon to intensified secondary electrons escape when the geomagnetic field lines are normal to conducting surfaces that emit secondary electrons. Since the magnitude of the artifact is only a few percent of the large‐scale background, it does not have a serious impact on the value of the Swarm/LP data in scientific research. Nevertheless, future efforts to determine the exact cause of the artifacts will contribute to improving the reliability and quality of plasma density and temperature measured by Swarm/LP.

Application of an Improved Calibration Flight Scheme in Aeromagnetic Interference Compensation

AbstractIn aeromagnetic measurement, accurate compensation for the interference magnetic field generated by the aircraft platform due to the aircraft maneuvering in the Earth's magnetic field is an important prerequisite for the accurate identification of the magnetic anomaly signal of the detection target. The flaws of the traditional calibration flight scheme in aeromagnetic interference compensation are firstly analyzed, and then an improved scheme is proposed, featuring smaller calibration flight areas, more simplified maneuvers, shorter flight route and less influence from the magnetometer's direction and extreme weather. The improved scheme can enhance the robustness of the aeromagnetic interference compensation matrix and improve the compensation efficiency, and thus both the solved magnetic compensation coefficients and compensation effects are significantly improved. The experimental results of the aeromagnetic interference compensation in an area of Inner Mongolia of China show that the average accuracy of the repeated survey lines, which are compensated by the improved scheme, can be increased by 5 and 3 nT, respectively, compared with the uncompensated results and the results compensated by the traditional scheme. Therefore, the effectiveness and superiority of the improved calibration flight scheme is fully proved.

Solar Wind Speed Prediction via Graph Attention Network

AbstractThe solar wind is a plasma flow formed by the expansion of the high‐temperature corona and propagates in the interplanetary space with speeds between 200 km/s and 900 km/s. Accurate solar wind speed prediction and longer lead time will help mitigate the impact of solar storms on aerospace equipment and the Earth's magnetic field. Recently, most approaches do not explicitly capture the relationships between different solar wind features, and the prediction accuracy of 96‐hr is still not good enough. This paper elaborately designs an end‐to‐end model: Graph‐Temporal‐AR model (GTA) for solar wind speed prediction. First, our framework considers each feature as the node to construct the graph structure and adopts the graph attention module to learn the complex dependencies among features. Second, our approach employs the dilated causal convolution to extend the receptive field and prolong the prediction time. Furthermore, we leverage the autoregressive model to solve the scale insensitive problem of the neural network, making our model more robust. Specifically, we combine the OMNI data measured at Lagrangian Point 1 (L1) with the extreme ultraviolet images observed by the Solar Dynamics Observatory satellite to predict the solar wind speed at L1. Compared with the baseline models, GTA obtains significant performance improvements. Through visualization, we find GTA excavates the relationships between multiply variables without domain prior knowledge, which may help us find other unknown associations in heliophysics data sets. The data and code are available from https://github.com/syrGitHub/GTA.