Earth's Field Research Articles

Chirped-frequency excitation of gravitationally bound ultracold neutrons

Ultracold neutrons confined in the Earth's gravitational field display quantized energy levels that have been observed for over a decade. In recent resonance spectroscopy experiments [T. Jenke et al., Nature Phys. 7, 468 (2011)], the transition between two such gravitational quantum states was driven by the mechanical oscillation of the plates that confine the neutrons. Here we show that, by applying a sinusoidal modulation with slowly varying frequency (chirp), the neutrons can be brought to higher excited states by climbing the energy levels one by one. The proposed experiment should make it possible to observe the quantum-classical transition that occurs at high neutron energies. Furthermore, it provides a technique to realize superpositions of gravitational quantum states, to be used for precision tests of gravity at short distances.

GPS and the Search for Axions

GPS, an excellent tool for geodesy, may serve also particle physics. In the presence of Earth's magnetic field, a GPS photon may be transformed into an axion. The proposed experimental setup involves the transmission of a GPS signal from a satellite to another satellite, both in low orbit around the Earth. To increase the accuracy of the experiment, we evaluate the influence of Earth's gravitational field on the whole quantum phenomenon. There is a significant advantage in our proposal. While geomagnetic field B is low, the magnetized length L is very large, resulting into a scale (BL)^2 orders of magnitude higher than existing or proposed reaches. The transformation of the GPS photons into axion particles will result in a dimming of the photons and even to a "light shining through the Earth" phenomenon.

Application of Vector Scalar Product to Solve the Kinematic Equations in the Earth's Gravitational Field

Application of Vector Scalar Product to Solve the Kinematic Equations in the Earth's Gravitational Field

Hybrid fluid‐particle simulation of whistler‐mode waves in a compressed dipole magnetic field: Implications for dayside high‐latitude chorus

AbstractIn this work we present a methodology for simulating whistler‐mode waves self‐consistently generated by electron temperature anisotropy in the inner magnetosphere. We present simulation results using a hybrid fluid/particle‐in‐cell code that treats the hot, anisotropic (i.e., ring current) electron population as particles and the background (i.e., the cold and inertialess) electrons as fluid. Since the hot electrons are only a small fraction of the total population, warm (and isotropic) particle electrons are added to the simulation to increase the fraction of particles with mass, providing a more accurate characterization of the wave dispersion relation. Ions are treated as a fixed background of positive charge density. The plasma transport equations are coupled to Maxwell's equations and solved in a meridional plane (a 2‐D simulation with 3‐D fields). We use a curvilinear coordinate system that follows the topological curvature of Earth's geomagnetic field lines, based on an analytic expression for a compressed dipole magnetic field. Hence, we are able to simulate whistler wave generation at dawn (pure dipole field lines) and dayside (compressed dipole) by simply adjusting one scalar quantity. We demonstrate how, on the dayside, whistler‐mode waves can be locally generated at a range of high latitudes, within pockets of minimum magnetic field, and propagate equatorward. The obtained dayside waves (in a compressed dipole field) have similar amplitude and frequency content to their dawn sector counterparts (in a pure dipole field) but tend to propagate more field aligned.

Comparison of the earth's crust geothermal field in Northern Tien Shan region with seismic characteristics

The deep crustal temperatures of the Northern Tien Shan region are being calculated on the basis of direct measurements of the heat flow and empirical relation of geothermal parameters and seismic velocities. For this purpose the applied method of numerical solution of conductive heat transfer equation takes into account additional sources of heat release due to radioactive decay. Thermoelastic deformations, reaching 20-40% of the total lithostatic pressure at depths of 35-60 km, are determined. The criteria controlling the distribution of hypocenters of earthquakes have been determined in accordance with the morphology of the regions of excess temperatures and thermal stresses.

Sensitivity of Atom Interferometry to Ultralight Scalar Field Dark Matter.

We discuss the use of atom interferometry as a tool to search for dark matter (DM) composed of virialized ultralight fields (VULFs). Previous work on VULF DM detection using accelerometers has considered the possibility of equivalence-principle-violating effects whereby gradients in the dark matter field can directly produce relative accelerations between media of differing composition. In atom interferometers, we find that time-varying phase signals induced by coherent oscillations of DM fields can also arise due to changes in the atom rest mass that can occur between light pulses throughout the interferometer sequence as well as changes in Earth's gravitational field. We estimate that several orders of magnitude of unexplored phase space for VULF DM couplings can be probed due to these new effects.

Archaeointensity results spanning the past 6 kiloyears from eastern China and implications for extreme behaviors of the geomagnetic field

Variations of the Earth's geomagnetic field during the Holocene are important for understanding centennial to millennial-scale processes of the Earth's deep interior and have enormous potential implications for chronological correlations (e.g., comparisons between different sedimentary recording sequences, archaeomagnetic dating). Here, we present 21 robust archaeointensity data points from eastern China spanning the past ∼6 kyr. These results add significantly to the published data both regionally and globally. Taking together, we establish an archaeointensity reference curve for Eastern Asia, which can be used for archaeomagnetic dating in this region. Virtual axial dipole moments (VADMs) of the data range from a Holocene-wide low of ∼27 to "spike" values of ∼166 ZAm2 (Z: 1021). The results, in conjunction with our recently published data, confirm the existence of a decrease in paleointensity (DIP) in China around ∼2200 BCE. These low intensities are the lowest ever found for the Holocene and have not been reported outside of China. We also report a spike intensity of 165.8 ± 6.0 ZAm2 at ∼1300 BCE (±300 y), which is either a prelude to or the same event (within age uncertainties) as spikes first reported in the Levant.

The plasmapause formation seen from meridian perspective by KAGUYA

AbstractObservations by the extreme ultraviolet (EUV) imager on board the IMAGE spacecraft revealed that the formation of a sharp plasmapause occurs in the postmidnight sector soon (<1 h) after the convection enhancement. These results cannot be explained simply by the conventional theory of the plasmapause formation that the plasmapause coincides with the last closed equipotential of the convection electric field superposed on the Earth's corotation electric field. However, due to the limitation that the EUV imager provides information on only the azimuthal distribution of the plasmapause, the formation mechanism still remains an open issue. Now global images of the plasmasphere from meridian perspective become available, thanks to the telescope of extreme ultraviolet (TEX) instrument on board the KAGUYA spacecraft. Here we studied the plasmapause formation mechanism by analyzing the sequential TEX images of an erosion event during the geomagnetic disturbance (Kp = 5) on 1–2 May 2008. The temporal evolution of the plasmapause locations at postmidnight observed by TEX agreed with those predicted by the dynamic simulations based on the interchange mechanism. Furthermore, the He+ column density in the nightside plasmasphere decreased by ~30% only at the low latitudes (<20°) during the enhanced convection period. This suggests that the plasmapause formation occurs first near the equatorial region during a geomagnetic disturbance, and it agrees with the plasmapause formation mechanism based on the interchange instability. Although we cannot conclude exclusively for the interchange mechanism, this is the first study to present the plasmapause formation viewed from the meridian perspective.

The algorithm for calculating the Earth's core runs on the parameters of natural pulsed electromagnetic field of the Earth

This paper presents the argumentation in favor of a hypothesis of the eccentric rotation of the Earth's shell and core. It covers the algorithm and computation of movement path and position of the Earth's core by the Earth's natural pulse electromagnetic field characteristics.

Magnetic Fields Modulate Blue-Light-Dependent Regulation of Neuronal Firing by Cryptochrome.

The biophysical mechanism of animal magnetoreception is still unclear. The photoreceptor protein cryptochrome has risen to prominence as a candidate magnetoreceptor molecule based on multiple reports derived from behavioral studies. However, the role of cryptochrome as a magnetoreceptor remains controversial primarily because of a lack of direct experimental evidence linking magnetic field (MF) exposure to a change in neuronal activity. Here, we show that exposure to an MF (100 mT) is sufficient to potentiate the ability of light-activated cryptochrome to increase neuronal action potential firing. Our results provide critical missing evidence to show that the activity of cryptochrome is sensitive to an external MF that is capable of modifying animal behavior.

POSSIBLE CAUSES OF CHANGE IN THE DIRECTION OF EARTH'S MAGNETIC FIELD

The study of the magnetic properties of materials have attracted the interest of scientists for ages. Knowing the magnetic properties of materials do their best possible use in industry and technology, as well as better understanding of some yet unexplained phenomena in nature related to the Earth's magnetic field. Several models that describe the given phenomenon are known, such as the domino model, two-dimensional Ising model and model of inversion magnetic Earth's field. In computer experiments whose results are presented in this paper, it is used a simplified two-dimensional Ising model, one version of the model related spins. Computer experiments (simulations) are made in the mathematical software Maple. It has been observed reversing the direction of magnetization in a small change of inhomogeneity energy interactions. Consideration of this issue could be of importance for the study of ferromagnetic material.

Are long tide gauge records in the wrong place to measure global mean sea level rise?

AbstractOcean dynamics, land motion, and changes in Earth's gravitational and rotational fields cause local sea level change to deviate from the rate of global mean sea level rise. Here we use observations and simulations of spatial structure in sea level change to estimate the likelihood that these processes cause sea level trends in the longest and highest‐quality tide gauge records to be systematically biased relative to the true global mean rate. The analyzed records have an average twentieth century rate of approximately 1.6 mm/yr, but based on the locations of these gauges, we show that the simple average underestimates the twentieth century global mean rate by 0.1 ± 0.2 mm/yr. Given the distribution of potential sampling biases, we find that <1% probability that observed trends from the longest and highest‐quality tide gauge records are consistent with global mean rates less than 1.4 mm/yr.

Quenching of antihydrogen gravitational states by surface charges

We study the effect of the quenching of antihydrogen quantum states near the surface of a material in the Earth's gravitational field by local charges randomly distributed along a mirror surface. The quenching reduces the probability of quantum reflection because of the additional atom–charge interaction, and thus the nonadiabatic transitions to excited gravitational states. Our approach is suitable when accounting for quenching caused by any kind of additional interaction with a characteristic range much smaller than the typical gravitational state wavelength.

Nonresonant interactions of electromagnetic ion cyclotron waves with relativistic electrons

AbstractThe dynamics of relativistic electrons traveling through a parallel‐propagating, monochromatic electromagnetic ion cyclotron (EMIC) wave in the Earth's dipole field are investigated via test particle simulations. Both resonant and nonresonant responses in electron pitch angle are considered, and the differences between the two are highlighted. Nonresonant electrons, with energies below the minimum resonant energy down to hundreds of keV, are scattered stochastically in pitch angle and can be scattered into the atmospheric loss cone. The nonresonant effect is attributed to the spatial edge associated with EMIC wave packets. A condition for effective nonresonant response is also provided. This effect is excluded from current quasi‐linear theory and can be a potentially important loss mechanism of relativistic and subrelativistic electrons in the radiation belts.

Gravitational effects on measurements of the muon dipole moments

If the technology for muon storage rings one day permits sensitivity to precession at the order of 10−8 Hz, the local gravitational field of Earth can be a dominant contribution to the precession of the muon, which, if ignored, can fake the signal for a nonzero muon electric dipole moment (EDM). Specifically, the effects of Earth's gravity on the motion of a muon's spin is indistinguishable from it having a nonzero EDM of magnitude dμ∼10−29 ecm in a storage ring with vertical magnetic field of ∼1 T, which is significantly larger than the expected upper limit in the Standard Model, dμ≲10−36 ecm. As a corollary, measurements of Earth's local gravitational field using stored muons would be a unique test to distinguish classical gravity from general relativity with a bonafide quantum mechanical entity, i.e., an elementary particle's spin.

Sunlight effects on the 3D polar current system determined from low Earth orbit measurements

Interaction between the solar wind and the Earth's magnetosphere is associated with large-scale currents in the ionosphere at polar latitudes that flow along magnetic field lines (Birkeland currents) and horizontally. These current systems are tightly linked, but their global behaviors are rarely analyzed together. In this paper, we present estimates of the average global Birkeland currents and horizontal ionospheric currents from the same set of magnetic field measurements. The magnetic field measurements, from the low Earth orbiting $\textit{Swarm}$ and CHAMP satellites, are used to co-estimate poloidal and toroidal parts of the magnetic disturbance field, represented in magnetic apex coordinates. The use of apex coordinates reduces effects of longitudinal and hemispheric variations in the Earth's main field. We present global currents from both hemispheres during different sunlight conditions. The results show that the Birkeland currents vary with the conductivity, which depends most strongly on solar EUV emissions on the dayside and on particle precipitation at pre-midnight magnetic local times. In sunlight, the horizontal equivalent current flows in two cells, resembling an opposite ionospheric convection pattern, which implies that it is dominated by Hall currents. By combining the Birkeland current maps and the equivalent current, we are able to calculate the total horizontal current, without any assumptions about the conductivity. We show that the total horizontal current is close to zero in the polar cap when it is dark. That implies that the equivalent current, which is sensed by ground magnetometers, is largely canceled by the horizontal closure of the Birkeland currents.

Magnetite Biomineralization in Magnetospirillum magneticum Is Regulated by a Switch-like Behavior in the HtrA Protease MamE

Magnetotactic bacteria are aquatic organisms that produce subcellular magnetic particles in order to orient in the earth's geomagnetic field. MamE, a predicted HtrA protease required to produce magnetite crystals in the magnetotactic bacterium Magnetospirillum magneticum AMB-1, was recently shown to promote the proteolytic processing of itself and two other biomineralization factors in vivo Here, we have analyzed the in vivo processing patterns of three proteolytic targets and used this information to reconstitute proteolysis with a purified form of MamE. MamE cleaves a custom peptide substrate with positive cooperativity, and its autoproteolysis can be stimulated with exogenous substrates or peptides that bind to either of its PDZ domains. A misregulated form of the protease that circumvents specific genetic requirements for proteolysis causes biomineralization defects, showing that proper regulation of its activity is required during magnetite biosynthesis in vivo Our results represent the first reconstitution of the proteolytic activity of MamE and show that its behavior is consistent with the previously proposed checkpoint model for biomineralization.

Gravitationally induced quantum transitions

In this letter, we calculate the probability for resonantly induced transitions in quantum states due to time dependent gravitational perturbations. Contrary to common wisdom, the probability of inducing transitions is not infinitesimally small. We consider a system of ultra cold neutrons (UCN), which are organized according to the energy levels of the Schr\"odinger equation in the presence of the earth's gravitational field. Transitions between energy levels are induced by an oscillating driving force of frequency $\omega$. The driving force is created by oscillating a macroscopic mass in the neighbourhood of the system of neutrons. The neutrons decay in 880 seconds while the probability of transitions increase as $t^2$. Hence the optimal strategy is to drive the system for 2 lifetimes. The transition amplitude then is of the order of $1.06\times 10^{-5}$ hence with a million ultra cold neutrons, one should be able to observe transitions.

Atmosphere-only GCM (ACCESS1.0) simulations with prescribed land surface temperatures

Abstract. General circulation models (GCMs) are valuable tools for understanding how the global ocean–atmosphere–land surface system interacts and are routinely evaluated relative to observational data sets. Conversely, observational data sets can also be used to constrain GCMs in order to identify systematic errors in their simulated climates. One such example is to prescribe sea surface temperatures (SSTs) such that 70 % of the Earth's surface temperature field is observationally constrained (known as an Atmospheric Model Intercomparison Project, AMIP, simulation). Nevertheless, in such simulations, land surface temperatures are typically allowed to vary freely, and therefore any errors that develop over the land may affect the global circulation. In this study therefore, a method for prescribing the land surface temperatures within a GCM (the Australian Community Climate and Earth System Simulator, ACCESS) is presented. Simulations with this prescribed land surface temperature model produce a mean climate state that is comparable to a simulation with freely varying land temperatures; for example, the diurnal cycle of tropical convection is maintained. The model is then developed further to incorporate a selection of “proof of concept” sensitivity experiments where the land surface temperatures are changed globally and regionally. The resulting changes to the global circulation in these sensitivity experiments are found to be consistent with other idealized model experiments described in the wider scientific literature. Finally, a list of other potential applications is described at the end of the study to highlight the usefulness of such a model to the scientific community.

A simple demonstration when studying the equivalence principle

The paper proposes a lecture experiment that can be demonstrated when studying the equivalence principle formulated by Albert Einstein. The demonstration consists of creating stroboscopic photographs of a ball moving along a parabola in Earth's gravitational field. In the first experiment, a camera is stationary relative to Earth's surface. In the second, the camera falls freely downwards with the ball, allowing students to see that the ball moves uniformly and rectilinearly relative to the frame of reference of the freely falling camera. The equivalence principle explains this result, as it is always possible to propose an inertial frame of reference for a small region of a gravitational field, where space-time effects of curvature are negligible.