Magnetic Field Oscillations Research Articles

Fabry-Pérot and Aharonov-Bohm interference in ideal graphene nanoribbons

Quantum-mechanical calculations of electron magneto-transport in ideal graphene nanoribbons are presented. In noninteracting theory, it is predicted that an ideal ribbon that is attached to wide leads should reveal Fabry-Perot conductance oscillations in magnetic field. In the theory with Coulomb interaction taken into account, the oscillation pattern should rather be determined by the Aharonov-Bohm interference effect. Both of these theories predict the formation of quasi-bound states, albeit of different structures, inside the ribbon because of strong electron scattering on the interfaces between the connecting ribbon and the leads. Conductance oscillations are a result of resonant backscattering via these quasi-bound states.

Poleward Moving Auroral Arcs and Pc5 Oscillations

AbstractWe present an example of one‐to‐one correspondence between poleward moving auroral arcs (PMAAs) and Pc5 oscillations observed at the Time History of Events and Macroscale Interactions during Substorms (THEMIS) Ground Based Observatory station Gillam. The PMAAs consisted of four successive intensifications (named PMAA1, PMAA2, PMAA3 and PMAA4) with a period of 3∼4 min over the magnetic latitudes from 68° to 70° in the auroral oval and varied coherently with the H‐component of magnetic field Pc5 oscillations. PMAA1 and PMAA2 appeared clearly at the magnetic latitude ∼69°, and the following two PMAAs, which were dimmer, appeared at the magnetic latitude ∼68°. PMAA1 and PMAA2 exhibited features of field‐line resonances with the maximum luminosity at the magnetic latitude ∼69.5° and ∼69.4°, respectively. The ground Pc5 oscillations were concurrent with toroidal mode Pc5 oscillation observed at the THEMIS‐D, ‐E, and ‐A satellites at ∼4 MLT in the outer magnetosphere. The magnetic and electric field oscillations at THEMIS were synchronized with the PMAAs. The magnetic energy of the THEMIS Pc5 oscillations is estimated using a numerical model of damped toroidal oscillations and compared with the kinetic energy of precipitating electrons associated with the field aligned current carried by the toroidal oscillations. The result reveals that the Pc5 magnetic energy is much larger than the kinetic energy, implying the magnetic energy is important for producing auroral emissions in the ionosphere. We also perform a simulation of the relationship between PMAAs and toroidal mode Pc5 oscillations. The simulation explains the observed spatial and temporal structures of the PMAAs.

Correlation between ST-elevation myocardial infarction, non-ST-elevation myocardial infarction and the local Earth’s magnetic field changes

Stronger oscillations in the local Earth magnetic field may have an impact on the course of ischemic heart disease. This effect is individual for every person and depends on the sex, age, living territory, season, capability to adjust to magnetic field fluctuations and health status. Individuals who already have cardiovascular disease are more sensitive to magnetic field fluctuations, therefore further research is needed to make conclusions. Aim: To identify correlations between changes in local Earth magnetic field frequencies and patients with ST segment elevation myocardial infarction (STEMI) and non-ST segment elevation myocardial infarction (NSTEMI) cases per week, cases by sex per week and patients’ blood laboratory parameters (low-density lipoprotein cholesterol and Troponin I level). Methods: A retrospective study of 1667 patients, who were admitted to the Hospital of Lithuanian University of Health Sciences Kaunas Clinics between 1st January and 31st December 2019 due to acute coronary syndrome (STEMI and NSTEMI), were included in the study. Local Earth's time varying magnetic field (TVMF) was measured by a magnetometer located in Baisogala, Lithuania. Data from the magnetometer was collected daily, and weekly averaged. We assessed the correlations between average weekly geomagnetic field strength in six different frequency ranges (Hz) and average number of STEMI and NSTEMI cases per week, cases by sex per week and patients’ blood laboratory parameters (low-density lipoprotein cholesterol and Troponin I level). Results: The presence of a stronger magnetic field in the frequency range of 32-65 Hz was significantly related to the number of cases in the STEMI group during the winter season (r= 0.583, p= 0.036). Tendency towards a positive correlation was found during the winter in the men's group with STEMI in the high frequency range of 32-65 Hz. Low-density lipoprotein cholesterol level correlated positively in the winter STEMI group with the magnetic field in the 32-65 Hz range, and in the autumn STEMI group with the magnetic field in the frequency range of 0-7 Hz. Conclusion: Increased geomagnetic field strength in the high frequency range of 32-65 Hz is associated with a higher number of cases in the STEMI group.

The Geoeffectiveness of Solar Wind Current Sheets and Its Modulation by Foreshock Ions

AbstractWe examined the evolution of 34 solar wind bifurcated current sheets in the magnetosheath and their magnetospheric responses, using the in‐situ observations of the THEMIS probes and the GOES satellites. The role of foreshock ions in that process is also determined. The first current sheet event did not exhibit any modulation by foreshock ions; it generated a dynamic pressure plateau, which further evolved into a dynamic pressure plateau in the magnetosheath and likely generated mirror mode waves in the magnetosphere. The second event exhibits foreshock ions which enhanced the perturbations in the current sheet due to the disappearance and reappearance of foreshock ions controlled by the direction changes of magnetic field. That current sheet further compressed the magnetosphere and drove stronger magnetic field oscillations than the first event. Thus, solar wind current sheets can be geoeffective and their geoeffectiveness can be amplified by the foreshock ions inside their structures.

Growth rate of azimuthal perturbation modes in an ideal annular linear induction pump

This study is aimed at investigating the growth rate of azimuthal perturbation modes in an ideal annular linear induction pump model. The positive growth rate of azimuthal perturbation modes is associated with the unstable behaviour of the annular linear induction pump and is known in the literature as MHD instability characterized by strong low-frequency oscillations of magnetic field, flowrate, and pressure. A linear stability analysis of a height-averaged quasi-stationary main flow in the ideal annular linear induction pump has been conducted, where only temporally evolving azimuthal modes of the axial velocity and magnetic field perturbations were considered. The obtained results predict damped or damped oscillating perturbations in a stable regime as a function of Rm, Rms, N and κm. In the studied parameter range, an amplification of perturbations without oscillations was observed above the instability threshold. It can be concluded that the analysed model of the ideal annular linear induction pump cannot predict experimentally and numerically the observed low frequency oscillations. Figs 4, Refs 17.

Magnetotransport signatures of antiferromagnetism coexisting with charge order in the trilayer cuprate HgBa2Ca2Cu3O8+\u03b4

Multilayered cuprates possess not only the highest superconducting temperature transition but also offer a unique platform to study disorder-free CuO2 planes and the interplay between competing orders with superconductivity. Here, we study the underdoped trilayer cuprate HgBa2Ca2Cu3O8+δ and we report quantum oscillation and Hall effect measurements in magnetic field up to 88 T. A careful analysis of the complex spectra of quantum oscillations strongly supports the coexistence of an antiferromagnetic order in the inner plane and a charge order in the outer planes. The presence of an ordered antiferromagnetic metallic state that extends deep in the superconducting phase is a key ingredient that supports magnetically mediated pairing interaction in cuprates.

2470 million-year-old banded iron formation reveals a climatic oscillation consistent with the Gleissberg solar cycle

Modern-day solar cycles due to the solar magnetic field oscillation are well recognized. Owing to the response of Earth’s climate to solar activity fluctuation, solar cycles in the Phanerozoic Eon have been recorded by laminites and fossil tree rings. However, the existence of magnetic cycles within the Sun younger than 3100 million-year-old is still unknown. The deposition of Precambrian banded iron formations (BIFs) reflects the primary productivity of the early ferruginous oceans and is coupled to climatic fluctuations. Here we apply synchrotron-radiation-based µ-XRF with a 20 µm interval on a 60 mm long, 2470 million-year-old BIF from the Kuruman Formation, South Africa. Our spectral analyses of multiple elemental concentration series reveal prominent and consistent 80-year cyclicity, which is best explained by the Gleissberg solar cycle. We hypothesize that solar cycles have already modulated the early Paleoproterozoic climate mainly through high energy irradiance coupled solar radiative forcing oscillation and the solar magnetic field controlled galactic cosmic ray fluctuation. Our result provides the record of solar magnetic field oscillations with stable and close-to-present cycle durations at least since the beginning of the Paleoproterozoic Era.

Feelings of Knowing - Fundamental Interoceptive Patterns (FoK-FIP): a magnetic monopole-like “pure mental” process fundamental to subjective feelings and self-awareness

ABSTRACT The Feelings of Knowing - Fundamental Interoceptive Patterns (FoK-FIP) is a transdisciplinary theory developed to explain elusive phenomena suspected to exist that do not easily lend themselves to empirical measurement. The FoK-FIP theory posits that specialized self-generated biomagnetism and “pure mental” process share similarities with the hypothetical elementary particle described in particle physics, magnetic monopoles with a magnetic charge. Feelings of Knowing (FoK) are “awareness charge” that are self-generated events. Fundamental Interoceptive Patterns (FIP) are restricted oscillatory magnetic fields that are FoK caused phenomena. Further, FoK produces “cognitive force,” an observing ego representing specialized interoceptive awareness. Through embodied states, FoK-FIP acts as a “biological node,” an informational processing unit in which physiological signals and an observing ego’s sensations or feelings are centered. An observing ego cognitively broadcasts using specialized small magnetic signals and four phases of a narrowed range of interoceptive signals. By defining interoceptive signals (i.e., signals of the body’s internal state) using FoK-FIP through cognitive broadcasting, an observing ego creates a world it projects around itself. This process is understood through the components map with interoceptive markers (IMs), a novel algorithm based on biological evolution. FoK-FIP-related predictions are described as are empirical studies to test aspects of the theory. The FoK-FIP theory details a path to wellbeing based on a sense of control and capacity for self-care. Mental stability is thought to change as a function of an observing ego’s volitional reactions.

A model for spin–orbit commensurability and synchronous starspot activity in stars with close-by planets

Context. The rotation period of some planet-hosting stars appears to be in close commensurability with the orbital period of their close-by planets. In some cases, starspots rotating with a commensurable period have been detected, while the star displays latitudinal differential rotation. Aims. A model is proposed to interpret such a phenomenon based on the excitation of resonant oscillations in the interior magnetic field of the star by a component of the tidal potential with a very low frequency in the reference frame rotating with the star. Methods. A magnetic flux tube located in the overshoot layer of the star is assumed in order to study the excitation of the resonant oscillations in the magnetostrophic regime. The model considers a planet on a circular oblique orbit, and the growth timescale of the oscillations is estimated. To keep the system in resonance with the exciting potential despite the variations in the magnetic field or tidal frequency, a self-regulating mechanism is proposed. Results. The model is applied to ten systems and proves capable of accounting for the observed close commensurability in eight of them by assuming a magnetic field between 102 and 104 G. Systems with distant low-mass planets, such as AU Mic and HAT-P-11, cannot be interpreted by the proposed model. Conclusions. Consequences for the spin–orbit evolution of the systems, including the dynamical tides and gyrochronology of planet-hosting stars, are discussed together with the effects on the chromospheric features produced by star–planet magnetic interactions.

Technique for Recording and Analysis of the Amplitude Spectrum of the Strength Oscillations of Magnetic and Electric Fields of Combustion Products in a Model Liquid Rocket Engine Fuel Depending on the Combustion Chamber Pressure

Technique for Recording and Analysis of the Amplitude Spectrum of the Strength Oscillations of Magnetic and Electric Fields of Combustion Products in a Model Liquid Rocket Engine Fuel Depending on the Combustion Chamber Pressure

Van Allen Probes Observations of Symmetric Stormtime Compressional ULF Waves.

Previous spacecraft studies showed that stormtime poloidal ultralow‐frequency (ULF) waves in the ring current region have an antisymmetric (second harmonic) mode structure about the magnetic equator. This paper reports Van Allen Probes observations of symmetric ULF waves in the postnoon sector during a moderate geomagnetic storm. The mode structure is determined from the presence of purely compressional magnetic field oscillations at the equator accompanied by strong transverse electric field perturbations. Antisymmetric waves were also detected but only very late in the recovery phase. The symmetric waves were detected outside the plasmasphere at L = 3.0–5.5 and had peak power at 4–10 mHz, lower than the frequency of the local fundamental toroidal standing Alfvén wave. During the wave events, the flux of protons was enhanced at energies below ∼5 keV, which appears to be a prerequisite for the waves. The protons may provide free energies to waves through drift resonance instability or drift compressional instability, which occur in the presence of radial gradients of plasma parameters.

Effect of extremely low-frequency magnetic fields on light-induced electric reactions in wheat

ABSTRACT Magnetic field oscillations resulting from atmospheric events could have an effect on growth and development of plants and on the responsive reactions of plants to other environmental factors. In the current work, extremely low-frequency magnetic field (14.3 Hz) was shown to modulate light-induced electric reactions of wheat (Triticum aestivum L.). Blue light-induced electric reaction in wheat leaf comprises depolarization and two waves of hyperpolarization resulting in an increase of the potential to a higher level compared to the dark one. Fluorescent and inhibitory analysis demonstrate a key role of calcium ions and calcium-dependent H+-ATPase of the plasma membrane in the development of the reaction. Activation of H+-ATPase by the increased calcium influx is suggested as a mechanism of the influence of magnetic field on light-induced electric reaction.

Токи смещения Фуко в динамике несимметричной системы

Рассмотрены пондеромоторные силы, действующие на незамкнутые токи проводимости Фуко в симметричном проводнике. Приведен пример симметричного проводника, находящегося в аксиально-симметричном внешнем переменном магнитном поле. Эти токи замыкаются токами смещения, на которые действует магнитное поле токов проводимости в проводнике, создавая силу Абрагама. Показано, что переменное магнитное поле, создаваемое токами смещения, не оказывает действие на токи проводимости в проводнике. Единственной магнитной силой, среднее значение которой за период изменения внешнего магнитного поля не равно нулю, является сила самодействия, с которой проводник действует сам на себя. Сумма сил Абрагама и самодействия равна нулю, что соответствует закону сохранения импульса. Сила тяги, роль которой играет сила самодействия, максимальна при наибольшей неоднородности источника внешнего переменного магнитного поля на его периферии.

Two-phase model of intravenous magnetic nanoparticle hyperthermia in muscle and prostate tumours

In this work, we investigate heat transfer phenomena in muscle and prostate tissues during magnetic hyperthermia cancer therapy with intravenously-injected maghemite nanoparticles. The resulting suspension of nanoparticles in blood is considered to be a non-Newtonian nanofluid, and a two-phase model that considers Brownian and thermophoretic effects is considered. The geometrical domain is comprised of a blood vessel region, cancerous and non-cancerous (prostate or muscle) tissue regions, and a region of fat tissue. The mixed finite element technique is utilized for solving the governing equations and their associated initial and boundary conditions; triangular quadratic elements are chosen for the temperature, velocity and nanoparticle volume fraction approximations, whereas triangular linear elements are selected for the pressure approximation. Based on this numerical solution, we examine the impact of the nanoparticle volume fraction at the inlet of the blood and magnetic field oscillation frequency on heat transfer and nanoparticle transport. The findings of this study indicate that in the prostate and muscle tissue cases, the nanoparticle distribution non-uniformity and the tissue and blood vessel temperatures are increased, and the average pressure is reduced, by increasing the inlet nanoparticle concentration and magnetic field oscillation frequency. In the muscle tissue case, the mean flow velocity can be increased by increasing the inlet nanoparticle concentration and decreasing the magnetic field oscillation frequency. Based on these findings, recommendations are made for improving the effectiveness of magnetic nanoparticle hyperthermia in cancerous muscle and prostate tissues. The research conducted in this work is motivated by the need for a better understanding of the factors impacting nanoparticle transport in tissues and heat generation during magnetic hyperthermia. Using the mathematical model developed herein, tissue temperatures attained under intravenous magnetic hyperthermia treatment can be accurately predicted.

Ratio Between Discrete IAR Frequencies From Observations in the Solar Cycle 24

Two types of standing Alfvén waves can exist in the ionospheric Alfvén resonator (IAR). The first of them (type 1) corresponds to the case when an antinode of oscillations of the magnetic field of a standing Alfvén wave occurs at the lower boundary of the resonator. The second type corresponds to the case when a node of magnetic field oscillations occurs at the lower boundary. The article proposes an original technique that makes it possible to experimentally determine which of the two indicated types is observed in the experiment. The methodology is based on the idea that in the first case the harmonics of oscillations are odd, i.e., are multiples of 3, 5, 7, and 9, while in the second case the harmonics are multiples of the fundamental frequency: 2, 3, 4, 5, and so on (type 2 of standing waves). Using ground-based observations of the IAR emissions at obs. Mondy from 2009 to 2019, we have shown that events with an odd ratio of harmonics are most often observed.

Comparative study of Dirac and Majorana ultrahigh-energy neutrino oscillations in an interstellar magnetic field

We examine the ultrahigh-energy neutrino propagation in interstellar space in the Dirac and Majorana cases. Employing the two-neutrino mixing approximation and using the astrophysical constraints on neutrino magnetic moments, we show that both the flavor and the spin oscillations of the Dirac and Majorana neutrinos exhibit qualitatively different behaviors in an interstellar magnetic field for neutrino-energy values characteristic of, respectively, the cosmogenic neutrinos and well above the Greisen-Zatsepin-Kuz’min cutoff.

Optical signatures of the coupled spin-mechanics of a levitated magnetic microparticle

We propose a platform that combines the fields of cavity optomagnonics and levitated optomechanics to control and probe the coupled spin-mechanics of magnetic dielectric particles. We theoretically study the dynamics of a levitated Faraday-active dielectric microsphere serving as an optomagnonic cavity, placed in an external magnetic field and driven by an external laser. We find that the optically driven magnetization dynamics induces angular oscillations of the particle with low associated damping. Further, we show that the magnetization and angular motion dynamics can be probed via the power spectrum of the outgoing light. Namely, the characteristic frequencies attributed to the angular oscillations and the spin dynamics are imprinted in the light spectrum by two main resonance peaks. Additionally, we demonstrate that a ferromagnetic resonance setup with an oscillatory perpendicular magnetic field can enhance the resonance peak corresponding to the spin oscillations and induce fast rotations of the particle around its anisotropy axis.

Structure of a Perturbed Magnetic Reconnection Electron Diffusion Region in the Earth's Magnetotail.

We report insitu observations of an electron diffusion region (EDR) and adjacent separatrix region in the Earth's magnetotail. We observe significant magnetic field oscillations near the lower hybrid frequency which propagate perpendicularly to the reconnection plane. We also find that the strong electron-scale gradients close to the EDR exhibit significant oscillations at a similar frequency. Such oscillations are not expected for a crossing of a steady 2D EDR, and can be explained by a complex motion of the reconnection plane induced by current sheet kinking propagating in the out-of-reconnection-plane direction. Thus, all three spatial dimensions have to be taken into account to explain the observed perturbed EDR crossing. These results shed light on the interplay between magnetic reconnection and current sheet drift instabilities in electron-scale current sheets and highlight the need for adopting a 3D description of the EDR, going beyond the two-dimensional and steady-state conception of reconnection.

Photopolymerized Thin Coating of Polypyrrole/Graphene Nanofiber/Iron Oxide onto Nonpolar Plastic for Flexible Electromagnetic Radiation Shielding, Strain Sensing, and Non‐Contact Heating Applications

AbstractThe current work presents the fabrication of micrometer‐thick single‐side‐coated surface‐engineered polypropylene (PP) film for versatile flexible electronics applications. Herein, the authors report, for the first time, photopolymerized thin coating of graphene nanofibers (GNFs) and iron oxide nanoparticles (IONPs) onto non‐polar plastic via surface chemistry. The fabrication is achieved by adopting three consecutive steps; initially corona treated PP films are treated with silane for thin layer silica coating. Then, the silylated PP films are brushed up by pyrrole/GNFs/IONPs mixture, followed by UV exposure. The coated films show surface conductivity in the range of ≈20 S cm−1 at room temperature. Moreover, ≈15 microns of the coated film is tested against electromagnetic waves in the X‐band region (8.2–12.4 GHz) and its shielding behavior (≈24 dB) is confirmed. To demonstrate its wide range of versatility, the coated films are tested against angular strain and oscillatory magnetic fields. The results confirm angle dependent strain sensitivity and induction heating obeying Néel relaxation. To the best of the authors’ knowledge, this is the first synergistic coating archived for mitigating radiation pollution, strain sensing, and non‐contact heating.

High-frequency magnetic response of superferromagnetic nanocomposites

Studies of the dynamical response of thin-film composites of magnetic nanoparticles embedded in dielectric matrices to the oscillatory magnetic field of the microwave-frequency range are performed using numerical simulations. Four soft-magnetic systems; (Co)0.42(MgF2)0.58, (Fe65Co35)0.57(SiO2)0.43, (Fe65Co35)0.75(Al2O3)0.25, (Fe65Co35)0.6(Al2O3)0.4, typical of a class of ”high-frequency ferromagnetic nanocomposites” are simulated. The necessary micromagnetic parameters are extracted from data within the model of random magnetic anisotropy (RMA). Those materials are candidates for use in micro-converters of power (inductors and transformers) due to their high saturation magnetization, high resistivity, and absence of intra-grain magnetic domains. Thus, they are able to create a high magnetic flux at low power losses. The simulations allow for an inspection into details of the spatial distribution of the oscillating magnetization. We predict noticeable differences in the ferromagnetic resonance (FMR) in different composites which are related to the shape of the static hysteresis. Operating ranges of the driving-field amplitude are related to the hysteresis width. Next to FMR, we analyze the magnetic response via the oscillatory motion of domain walls in a longitudinal field. Besides the response to the alternating field of a constant direction, we study the magnetization dynamics driven by in-the-plane-rotating field. Such a field can drive the magnetization rotations which are a strong-response (nonlinear) mode potentially useful for efficient power conversion.