Importance of magnetic information for neuronal plasticity in desert ants

In this paper, I present a low-cost interactive experiment for measuring the strength of Earth's local magnetic field. This activity can be done in most high schools or two-year physics laboratories with limited resources, yet will have a tremendous learning impact. This experiment solidifies the three-dimensional nature of Earth's magnetic field vector and helps reinforce the aspect of the vertical component of Earth's magnetic field. Students should realize that Earth's magnetic field is not fully horizontal (except at the magnetic equator) and that a compass simply indicates the direction of the horizontal component of Earth's magnetic field. A magnetic dip needle compass can be used to determine the angle (known as the “dip angle” or “inclination angle”) measured from the direction in which Earth's magnetic field vector points to the horizontal. In this activity, students will be able to determine the horizontal component of the field using a Helmholtz coil and, knowing the dip angle, the Earth's magnetic field strength can be determined.

The blind mole rat Spalax ehrenbergi is a solitary, subterranean rodent that digs and inhabits a system of branching tunnels, with no above-ground exits, which it never leaves unless forced to. To survive, the mole rat must be able to orient efficiently in its tunnel system. The sensory channels available for spatial orientation in the subterranean environment are restricted in comparison with those existing above ground. This study examined the possibility that the mole rat is able to perceive and use the earth's magnetic field to orient in space. Experiments were performed using a device constructed from a pair of electromagnetic 'Helmholtz coils', which create a magnetic field whose direction and strength can be altered. In the first experiment, we tested a group of mole rats (N=33) in an eight-armed maze under the earth's natural magnetic field to determine whether they have directional preferences for the location of their sleeping nest, food chamber and toilet site. A second group of mole rats (N=30) was tested for their directional preference after the earth's magnetic field had been experimentally shifted by 180 degrees. We found that the first group exhibited a significant preference (P<0.001) to build both their sleeping nest and their food store in the southern sector of the maze, whereas the second group shifted the location of their nests (P<0.01) and food store (P<0.05), to the northern sector of the maze, corresponding to the shift in the magnetic field. In the second experiment, we tested whether the magnetic compass orientation found in the first experiment depends on a light stimulus by testing a group of mole rats in the eight-armed maze under total darkness. No significant difference in directional preference between light and dark test conditions was observed. It can be concluded, therefore, that, in contrast to some amphibians and birds, magnetic compass orientation in the mole rat is independent of light stimulation. In the third experiment, we examined whether mole rats (N=24) use the earth's magnetic field as a compass cue to orient in a labyrinth. In the first stage (trials 1-13), the animals were trained to reach a goal box at the end of a complex labyrinth until all individuals had learned the task. In the second stage (trial 14), half the trained mole rats underwent another labyrinth trial under the earth's natural magnetic field, while the other half were tested under a magnetic field shifted by 180 degrees. We found a significant decrease (P<0.001) in performance of the mole rats tested under the shifted magnetic field compared with the group tested under the natural magnetic field. The findings from these experiments prove that the mole rat is able to perceive and use the earth's magnetic field to orient in space.

The article discusses a field geophysical complex that includes the Earth's gravity and magnetic fields parameters meters — an digital zenith camera (DZC), a relative gravimeter, onboard quantum magnetometer and ground magnetovariation station. This complex allows determining such parameters of the Earth's gravity field as acceleration and anomalies of gravity, plumb line deviations, horizontal components of the acceleration of gravity and gravitational gradients, and parameters of the Earth's magnetic field — absolute and anomalous values of induction. Maps of the Earth's gravity and magnetic fields can be used in various fields, in particular, in the creation and testing of integrated autonomous navigation systems using the parameters of these fields. The paper presents examples of parameter maps created using this complex. The measurement error of acceleration and gravity anomaly is 10 µGal, plumb line deviation is ≈ 0.2″, horizontal components of gravity acceleration are ≈ 1 mGal, gravitational gradients are 10 Eötvös at a distanc

The results of calculations of the effi ciency of the shielding of a photoelectronic spectrometer by amorphous alloys, designed to protect the instrument from the Earth's magnetic fi eld, are presented. The distribution of the magnetic induction inside the shield for different positions of the instrument is measured. The anisotropy of the shielding properties of a magnetopolymer shield is investigated. An analysis of modern trends in investigating the effect of physical fi elds, in particular, the Earth's magnetic fi eld, on technical devices shows that most attention is being devoted to fi nding optimal methods of shielding (1-4). There are a number of instruments available at present, the readings of which are sensitive to the Earth's magnetic fi eld. These include instruments which use the physical laws of motion of charged particles in magnetic and electric fi elds: mass spectrometers, scanning electron microscopes, x-ray fl uorescent spectrometers, etc. Both static and variable magnetic fi elds of different fre- quency can defl ect particles from their normal trajectories of motion and thereby distort the readings of such instruments. Another form of magnetically sensitive devices is systems by means of which one can measure extremely small magnetic fi elds. For example, the magnetocardiograph, designed to carry out medical diagnostics, detects magnetic fi elds, the source of which is the heart. These fi elds are very weak, and hence it is important to eliminate the effect of induced external magnetic fi elds on the results of the measurements. An electromagnetic shield is a necessary part of the cabinet containing the magnetic tomography apparatus. If its integrity is disturbed or there is no shielding, extensive techniques cannot be correctly used, in view of the magnetic interference produced by surrounding electronic equipment and the geomagnetic fi eld. Standards in the area of the electromagnetic compatibility of technical instruments lay down the requirements for stability to electromagnetic interference, the quality of the electric power in the networks, and new methods of testing (5, 6). In practice, one cannot always transport the technical equipment a distance at which the fi eld is reduced to the thresh- old limit value. In this case, it is necessary to use shielding materials. The shielding of constant and low-frequency magnetic fi elds is the most complicated operation. For such purposes, one requires materials possessing high magnetic permeability and saturation induction, and low coercive force. They should remain capable of operating in diffi cult working conditions: they must be insensitive to mechanical and dynamic disturbances (deformations and vibrations), they must operate over a wide temperature range, and must have highly reproducible properties. To protect measuring instruments from the effect of extraneous physical fi elds, they are often placed in massive closed casings made of ferromagnetic material - usually permalloy. However, these shields have considerable drawbacks: the high shielding factor is not retained under mechanical actions, which inevitably arise during the manufacture and assembling the

The Zakarpattia internal trough is characterized by periodic seismicity, with local earthquakes of various energy classes recorded here: from weak tremors detected only by instruments to strong ones that cause certain destruction and are already felt by the population of the region. The seismicity of the region is accompanied by the response of the parameters of various geophysical fields: the Earth's magnetic field, electromagnetic emission, and radioactive background of the environment. The stress-strain state of the Earth's crust is influenced by factors of the meteorological and hydrogeological state of the region, which can accelerate or slow down seismotectonic processes in an earthquake-prone region. It is important to investigate the interrelationships of various geophysical fields in the time intervals of increasing seismicity in the region. We studied the relationships between the parameters of the Earth's magnetic field and the parameters and geodynamic states of the region, and noted the consistency of the anomalies of the Earth's magnetic field, the seismicity of the region, and the current horizontal crustal movements in the Oash Deep Rift zone. The responses of the radioactive background of the environment to the seismotectonics of the region were also studied, and an increase in the studied parameter was noted before intense crustal movements and the manifestation of local seismicity. The influence of geomechanical processes on the variations of electromagnetic emission was also studied, which indicated their connection, electromagnetic emission in different ranges of observation responded to crustal movements and local seismicity. It is important to understand the geodynamic and seismic processes to understand the response of the fields to their dynamics of change. The purpose of the article is to study the temporal variations of geophysical field parameters, their dynamics, and their mutual influence. The object of the study is variations of electromagnetic emission in different frequency ranges, variations of the Earth's magnetic field, dynamics of changes in the Earth's magnetic field. The subject of the study is the relationship between the parameters of the Earth's magnetic field and the parameters of electromagnetic emission, and the identification of their features. Methodology. To achieve this goal, we used the results of comprehensive geophysical observations in the Transcarpathian Inner Trough, which is being conducted by the Seismicity Department of the Carpathian Region of the Subbotin Institute of Geophysics of the National Academy of Sciences of Ukraine in 2023. Measurements of electromagnetic emission and the magnetic induction vector of the Earth's magnetic field are carried out at the Trosnyk geophysical station. The dynamic characteristics of the Earth's magnetic field were calculated, and a correlation analysis of electromagnetic emission and the Earth's magnetic field was performed. The obtained results are important for studying geological processes in the region, investigating the response of geophysical fields to environmentally hazardous processes, selecting optimal and effective methods and geophysical fields for future forecasting of underground shocks. Based on the results of geophysical observations, important conclusions were drawn regarding the relationship between electromagnetic emission and the Earth's magnetic field and the frequencies of electromagnetic emission that are most correlated with each other. It was found that the highest degree of connection between the Earth's magnetic field and electromagnetic emission in the range of 2 kHz is equal to: 0.4. The results obtained indicate the low-frequency component of the electromagnetic emission of the environment in connection with the Earth's magnetic field.

Robust attitude and heading estimation with respect to a known reference is an essential component for indoor localization in robotic applications. Affordable Attitude and Heading Reference Systems (AHRS) are typically using 9-axis solid-state MEMS-based sensors. The accuracy of heading estimation on such a system depends on the Earth's magnetic field measurement accuracy. The measurement of the Earth's magnetic field using MEMS-based magnetometer sensors in an indoor environment, however, is strongly affected by external magnetic perturbations. This paper presents a novel approach for robust indoor heading estimation based on skewed-redundant magnetometer fusion. A tetrahedron platform based on Hall-effect magnetic sensors is designed to determine the Earth's magnetic field with the ability to compensate for external magnetic field anomalies. Additionally, a correlation-based fusion technique is introduced for perturbation mitigation using the proposed skewed-redundant configuration. The proposed fusion technique uses a correlation coefficient analysis for determining the distorted axis and extracts the perturbation-free Earth's magnetic field vector from the redundant magnetic measurement. Our experimental results show that the proposed scheme is able to successfully mitigate the anomalies in the magnetic field measurement and estimates the Earth's true magnetic field. Using the proposed platform, we achieve a Root Mean Square Error of 12.74° for indoor heading estimation without using an additional gyroscope.

Local acceleration via whistler wave and particle interaction plays a significant role in particle dynamics in the radiation belt. In this work we explore gyroresonant wave‐particle interaction and quasi‐linear diffusion in different magnetic field configurations related to the 17 March 2013 storm. We consider the Earth's magnetic dipole field as a reference and compare the results against nondipole field configurations corresponding to quiet and stormy conditions. The latter are obtained with the ring current‐atmosphere interactions model with a self‐consistent magnetic field (RAM‐SCB), a code that models the Earth's ring current and provides a realistic modeling of the Earth's magnetic field. By applying quasi‐linear theory, the bounce‐ and Magnetic Local Time (MLT)‐averaged electron pitch angle, mixed‐term, and energy diffusion coefficients are calculated for each magnetic field configuration. For radiation belt (∼1 MeV) and ring current (∼100 keV) electrons, it is shown that at some MLTs the bounce‐averaged diffusion coefficients become rather insensitive to the details of the magnetic field configuration, while at other MLTs storm conditions can expand the range of equatorial pitch angles where gyroresonant diffusion occurs and significantly enhance the diffusion rates. When MLT average is performed at drift shell L=4.25 (a good approximation to drift average), the diffusion coefficients become quite independent of the magnetic field configuration for relativistic electrons, while the opposite is true for lower energy electrons. These results suggest that, at least for the 17 March 2013 storm and for L≲4.25, the commonly adopted dipole approximation of the Earth's magnetic field can be safely used for radiation belt electrons, while a realistic modeling of the magnetic field configuration is necessary to describe adequately the diffusion rates of ring current electrons.

Natural variations of the Earth's magnetic field and its man-made distortions are considered. The rules and regulations in force in the Russian Federation for staying and living in places with a distortion of the Earth's magnetic field are analyzed. Existing methods for eliminating distorted magnetic fields inside residential and work premises are considered. Modeling of distortions of the Earth's magnetic field by building materials was carried out and the influence of their location in space on the overall picture of the resulting magnetic field was shown. To modeling the influence of reinforcement of reinforced concrete constructions on the resulting magnetic field, 6 models of the location of reinforcing bars and their groups were used: one reinforcing bar magnetized against the Earth’s magnetic field and along the Earth’s field; 4 reinforcing bars each, magnetized against the Earth’s magnetic field and magnetized in an alternating manner; the simplest model of a residential structure or public building with 36 reinforcing bars magnetized against the Earth’s magnetic field and with 36 magnetized bars in different directions. Near the model of a rod with magnetization along the Earth’s magnetic field, there are hypogeomagnetic fields. Near the models of a reinforcing bar and four reinforcing bars magnetized against the Earth’s magnetic field, there are no hypogeomagnetic zones and changes in the direction of the magnetic field strength vectors, but strong increases in the resulting magnetic field can be observed - 500 times or more. Near models with 4 reinforcing bars magnetized in an alternating manner, there are the most dangerous zero values of magnetic field strength at a distance of 1 m. Inside the model with 36 reinforcing bars there is a hypogeomagnetic field in the very center of the model and a change in the direction of the magnetic field strength vectors. Near the model with 36 magnetized rods in different directions, a more even resulting magnetic field is observed without sharp changes in its direction and absolute value. Methods have been proposed for eliminating magnetic pathogenic zones at the stages of installation and construction of building that have ferromagnetic materials in their design.

The mushroom body

Applying a matrix method of electromagnetic induction in a multi-layered earth to estimating the shielding effect of the earth conductor on geomagnetic secular change, we evaluated the source current system of the earth's magnetic non-dipole field which was separated into two parts, a standing field and a drifting one, by Yukutake and Tachinaka. To determine the radii of the source current shells we constructed a velocity model corresponding to the differential rotation of the fluid core by considering the skin effect and the charactristic drift velocity of the secular change. Thus located positions of the current shells are compatable with those from statistics. The energy dissipation estimated for each current shell is of the order of one-tenth to one-thousandth of that of the dynamo of the dipole field. A discussion concerning the resultant current system shows that the model, by which the earth's magnetic field has been separated into two parts, is acceptable.

A variant of the thermoelectric model of the Earth's dipole magnetic field is considered. It is based on geothermoelectric currents present in the planet's core. The currents cyclically change their direction, which leads over time either to warming on the Earth, if their movement is directed towards the Earth's crust, or to cooling, when moving towards the inner core. With each change in the direction of movement of the thermal currents, the poles of the Earth's magnetic field are inverted simultaneously. The inversion process is instantaneous (on the scale of planetary time) and is not the result of a gradual reversal on the 180° Earth's magnetic axis. At the moment of inversions of thermal currents in the core, the total geomagnetic field decreases to the level of 4.6∙10-6 T, which is constantly supported by thermal currents of semi-conducting rocks of the lower mantle. The considered version of the thermoelectric model of the Earth's magnetic field may be promising for studying the magnetic fields of planets in the Solar system.

The Earth's magnetic field has not been mined as a source of energy for electrical power. With average field strength of .00005 Tesla around the world it is easy to understand why it has been overlooked. A disruptive technology is needed to mine the Earth's magnetic field as a power source. Such a technology, graphene, is now at an early stage of development with excellent properties in the form of high conductivity, low resistivity sheets that are durable, lightweight, and low cost. Electrical properties of multiple sheets of graphene provide a significant multiplier to Earth's weak magnetic field yielding a feasible source of ecologically clean power.

Efficient spatial orientation in the natural environment is crucial for the survival of most animal species. Cataglyphis desert ants possess excellent navigational skills. After far-ranging foraging excursions, the ants return to their inconspicuous nest entrance using celestial and panoramic cues. This review focuses on the question about how naïve ants acquire the necessary spatial information and adjust their visual compass systems. Naïve ants perform structured learning walks during their transition from the dark nest interior to foraging under bright sunlight. During initial learning walks, the ants perform rotational movements with nest-directed views using the earth’s magnetic field as an earthbound compass reference. Experimental manipulations demonstrate that specific sky compass cues trigger structural neuronal plasticity in visual circuits to integration centers in the central complex and mushroom bodies. During learning walks, rotation of the sky-polarization pattern is required for an increase in volume and synaptic complexes in both integration centers. In contrast, passive light exposure triggers light-spectrum (especially UV light) dependent changes in synaptic complexes upstream of the central complex. We discuss a multisensory circuit model in the ant brain for pathways mediating structural neuroplasticity at different levels following passive light exposure and multisensory experience during the performance of learning walks.

Desert ants of the genus Cataglyphis undergo an age-related polyethism from interior workers involved in brood care and food processing to short-lived outdoor foragers with remarkable visual navigation capabilities. The quick transition from dark to light suggests that visual centers in the ant's brain express a high degree of plasticity. To investigate structural synaptic plasticity in the mushroom bodies (MBs)-sensory integration centers supposed to be involved in learning and memory-we immunolabeled and quantified pre- and postsynaptic profiles of synaptic complexes (microglomeruli, MG) in the visual (collar) and olfactory (lip) input regions of the MB calyx. The results show that a volume increase of the MB calyx during behavioral transition is associated with a decrease in MG numbers in the collar and, less pronounced, in the lip. Analysis of tubulin-positive profiles indicates that presynaptic pruning of projection neurons and dendritic expansion in intrinsic Kenyon cells are involved. Light-exposure of dark-reared ants of different age classes revealed similar effects. The results indicate that this structural synaptic plasticity in the MB calyx is primarily driven by visual experience rather than by an internal program. This is supported by the fact that dark-reared ants age-matched to foragers had MG numbers comparable to those of interior workers. Ants aged artificially for up to 1 year expressed a similar plasticity. These results suggest that the high degree of neuronal plasticity in visual input regions of the MB calyx may be an important factor related to behavior transitions associated with division of labor.

A first regional model of the past Earth's magnetic field from Africa for the last 4000 years