scholarly journals Magnetic maps in animal navigation

2022 ◽  
Author(s):  
Kenneth J. Lohmann ◽  
Kayla M. Goforth ◽  
Alayna G. Mackiewicz ◽  
Dana S. Lim ◽  
Catherine M. F. Lohmann
Keyword(s):  
Magnetic Field ◽  
Positional Information ◽  
Natal Philopatry ◽  
Earth’S Magnetic Field ◽  
Long Distance ◽  
Natal Homing ◽  
Potential Source ◽  
Animal Navigation ◽  
Earth's Magnetic Field ◽  
The Magnetic Field

AbstractIn addition to providing animals with a source of directional or ‘compass’ information, Earth’s magnetic field also provides a potential source of positional or ‘map’ information that animals might exploit to assess location. In less than a generation, the idea that animals use Earth’s magnetic field as a kind of map has gone from a contentious hypothesis to a well-established tenet of animal navigation. Diverse animals ranging from lobsters to birds are now known to use magnetic positional information for a variety of purposes, including staying on track along migratory pathways, adjusting food intake at appropriate points in a migration, remaining within a suitable oceanic region, and navigating toward specific goals. Recent findings also indicate that sea turtles, salmon, and at least some birds imprint on the magnetic field of their natal area when young and use this information to facilitate return as adults, a process that may underlie long-distance natal homing (a.k.a. natal philopatry) in many species. Despite recent progress, much remains to be learned about the organization of magnetic maps, how they develop, and how animals use them in navigation.

A Study of the Magnetic Field of the Moon

1962 ◽  
Vol 14 ◽  
pp. 45-52 ◽  
Author(s):  
S. S. Dolginov ◽  
E. G. Eroshenko ◽  
L. I. Zhuzgov ◽  
N. V. Pushkov
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
The Moon ◽  
Earth’S Magnetic Field ◽  
Earth's Magnetic Field ◽  
The Magnetic Field

The question as to whether the planets and their satellites possess magnetic fields unavoidably arose in connection with the question as to the origin of the Earth's mágnetic field and the nature of a number of geophysical effects.

Study of the Magnetic Fields of Residential Buildings and their Impact on Human Health

2021 ◽  
Vol 23 (4) ◽  
pp. 370-382
Author(s):  
Radka Kostadinova ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Residential Buildings ◽  
Health Condition ◽  
Residential Areas ◽  
Earth’S Magnetic Field ◽  
The People ◽  
Specific Device ◽  
Earth's Magnetic Field ◽  
The Magnetic Field

With the prosperity of civilization people are more often put to the vibrations of the Earth’s magnetic field, which they are affecting by themselves in various ways. Settlements and residential areas, distant and electrical conductors, with its constantly changing electromagnetic field create strong deformations and weaken the Earth’s magnetic field. Is it possible that the reduction of the magnetic fields, in such buildings, to lead to illness and discomfort of the people living there. Is it possible that chronic discomfort and illness of the humans who inhabit those buildings don’t suffer from conditions, we usually connect with junk food, polluted air and the our stressful lifestyle, but are actually a result of the greatly reduced and changing magnetic field in the populated areas. With the research project developed by Tereza Stefanova with the help of students from the school, we tried to answer these questions. The purpose of our research is to: 1. Measure the magnetic field in buildings in our city, which differ by their construction and height and also to measure outside the city. 2. Determine if the change of the magnetic field and possible magnetic anomalies affect our health condition. The tasks we had to do to achieve our goal is to do take the measurements with a specific device.

scholarly journals An experiment on the origin of the earth's magnetic field

1923 ◽  
Vol 104 (727) ◽  
pp. 451-455 ◽  
Keyword(s):  
Magnetic Field ◽  
Slight Modification ◽  
Residual Effects ◽  
Earth’S Magnetic Field ◽  
Gravitational Action ◽  
Earth's Magnetic Field ◽  
Intimate Mixture ◽  
The Many ◽  
The Magnetic Field ◽  
Accepted Form

Of the many suggestions which have been made as to the origin of the earth’s magnetic field, perhaps the most promising is that it may be due to a slight modification of the laws of electrodynamics from the commonly accepted form. Electrically neutral matter is believed to consist of an intimate mixture of enormous amounts of positive and negative electricities, the electric and magnetic effects of which are usually supposed to balance each other. If the balance were not quite exact then small residual effects would be expected, among which gravitation and the earth’s magnetic field might be included. On such an hypothesis we might expect moving matter to produce a magnetic field similar to the field due to moving electricity, and we should expect some relation between the magnetic field due to moving matter and its gravitational action.

Magnetic Anomalies as a Reference for Ground-speed and Map-matching Navigation

1982 ◽  
Vol 35 (2) ◽  
pp. 242-254 ◽  
Author(s):  
Carl Tyrén
Keyword(s):  
Magnetic Field ◽  
Navigation Systems ◽  
Earth’S Magnetic Field ◽  
Electrical Field ◽  
Electrical Fields ◽  
Ground Speed ◽  
The Earth ◽  
Earth's Magnetic Field ◽  
Potential Basis ◽  
The Magnetic Field

The Earth's magnetic field has long provided us with a directional reference of almost worldwide usable coverage. This paper examines the use of the magnetic field for ground referenced motion and position measurementsWhere E is the vector representation of an electrical field, v vehicle velocity and B a magnetic field, the electromagnetic law of induction, E = v × B, indicates one possibility for measuring ground speed; the magnetic and electrical fields experienced by vehicle mounted sensors being used to solve the equation for v. This method however only gives the component of v perpendicular to the magnetic field. There are also certain difficulties associated with the measurement of B, which should be only the magnetic field of the Earth at the location of the vehicle, and E, which should be only the electrical field resulting from vehicle motion relative to the magnetic field of the Earth. The main problem appears to be the inseparability of motion dependent and non dependent electrical fields, a problem analogous to that of gravitation-acceleration inseparability for inertial navigation systems. The relative magnitudes of the vehicle-motiondependent E-field, of the order of 10−5 (volt/metre)/(metre/second), and the ever-present and very variable non-motion-dependent E-field between a highly conductive atmospheric layer at an altitude of about 50 km and the surface of the Earth, of some 102 volt/metre, are particularly unfavourable. Another potential basis for a ground-speed measurement system is the heterogeneous character of the intensity of the Earth's magnetic field.

7. The Earth’s magnetic field

2018 ◽  
pp. 106-126
Author(s):  
William Lowrie
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
Plate Tectonics ◽  
Magnetic Anomalies ◽  
Earth’S Magnetic Field ◽  
The Earth ◽  
Earth's Magnetic Field ◽  
Reversed Polarity ◽  
Harmful Radiation ◽  
The Magnetic Field

The Earth is surrounded by a magnetic field, which originates inside its molten core, and which for centuries has helped travellers to navigate safely across uncharted regions. The magnetic field protects life on the Earth by acting as a shield against harmful radiation from space, especially from the Sun. ‘The Earth’s magnetic field’ explains that the magnetic field at the Earth’s surface is dominantly that of an inclined dipole. The Sun’s deforming effect on the magnetic field outside the Earth is described, as are the magnetic fields of other planets. The magnetism of rocks forms the basis of palaeomagnetism, which explains how plate tectonics displaced the continents and produced oceanic magnetic anomalies whenever the geomagnetic field reversed polarity.

MAGNETIC PROPERTY AND CRITICAL CURRENT OF BiSrCaCuO SYSTEM UNDER LOW MAGNETIC FIELD

1989 ◽  
Vol 03 (06) ◽  
pp. 505-508
Author(s):  
L.Z. CAO ◽  
Y. YUE ◽  
J. WANG ◽  
S.D. MAO ◽  
H.B. LIU ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Property ◽  
Critical Current ◽  
Critical Field ◽  
Current Density ◽  
Pinning Force ◽  
Earth’S Magnetic Field ◽  
Earth's Magnetic Field ◽  
Low Magnetic Field ◽  
The Magnetic Field

The low critical field H c1 is determined by a.c.χ versus H and M versus H. For a sample of BiSrCaCuO with T c (0)=89 K , H c1 is equal to 17.5 Oe at 77 K. Measurement of the critical current Jc under low magnetic field shows that there is a peak on J c -H curve at about 1 Oe due to the existence of the earth’s magnetic field and the current density is very small in the BiSrCaCuO system and J c is nearly zero when the magnetic field reaches 150 Oe. It is suggested that the pinning force is very weak in this material.

scholarly journals Changes in the geomagnetic field has little effect on the overwintering range of Eastern North American fall migratory monarch butterflies (Danaus plexippus), indicating a lack of an innate magnetic map sense for navigation

2020 ◽  
Author(s):  
Patrick Anthony Guerra ◽  
Stephen Matter
Keyword(s):  
Magnetic Field ◽  
North American ◽  
Geomagnetic Field ◽  
Danaus Plexippus ◽  
Monarch Butterfly ◽  
Central Mexico ◽  
Earth’S Magnetic Field ◽  
Long Distance ◽  
Monarch Butterflies ◽  
Earth's Magnetic Field

Abstract BackgroundIndividuals of many species that perform annual long-distance migrations are capable of stopping at specific overwintering destinations, despite having not been there before. The iconic monarch butterfly (Danaus plexippus) and its annual long-distance fall migration is a famous example of this phenomenon. During the fall, Eastern North American monarch butterflies use various compass mechanisms to properly orient their flight southwards, in order to leave their summer breeding grounds in Southern Canada and the Northern United States, and reach their overwintering sites in Central Mexico. It remains a mystery, however, how monarchs locate and stop at these specific, consistent overwintering sites, especially since these individuals are on their maiden voyage. MethodsWe test the hypothesis that fall migrant monarchs locate these overwintering sites by using an innate, inherited map sense based on sensing and responding to specific geomagnetic signatures that are correlated with the overwintering sites. Using a natural displacement approach, we examined if the locations of overwintering sites and the abundance of monarchs at them, changes with the natural shift of the Earth’s magnetic field over time (2004-2018).ResultsWe found that despite the natural displacement of the geomagnetic field over the years, the locations of the overwintering sites and monarch abundance were unaffected. For example, fall monarchs continued to overwinter at the most southern sites in Mexico, even when the geomagnetic coordinates associated with these sites would have shifted north due to the natural shift of the Earth’s magnetic field, placing these sites significantly outside the range of the overwintering area.ConclusionsOur results suggest that monarchs do not employ a map sense based on geomagnetic cues for finding their overwintering sites, and might instead use other mechanisms or strategies for locating them (potentially using localized sensory cues) once they are near or have arrived in Central Mexico. We suggest that future work should now focus on understanding what these cue parameters are, in order to inform conservation efforts that are aimed at protecting the threatened monarch butterfly and preserving its annual long-distance migration.

scholarly journals The Earth's magnetic field in Southern Africa at the epoch, 1 July 1930

1947 ◽  
Vol 240 (818) ◽  
pp. 251-294 ◽  
Keyword(s):  
Magnetic Field ◽  
High Rate ◽  
Earth’S Magnetic Field ◽  
Magnetic Elements ◽  
Magnetic Inclination ◽  
Actual Observation ◽  
Earth's Magnetic Field ◽  
South West Africa ◽  
Linear Manner ◽  
The Magnetic Field

This paper is an attempt to determine the earth’s magnetic field in that part of Africa lying to the south of the Zambesi and Kunene Rivers, at the epoch 1930-50. The data used are: (1) Measurements made at about seven hundred stations by a number of previous workers, during the period 1900 to 1925, and already published. (2) Observations at about fifty of these stations made by the present writer between 1928 and 1930. These have been used to determine the secular variation, and thus to deduce the 1930-50 values of the magnetic field at all the other stations. The magnetic inclination is found to have changed in an almost linear manner, the maximum rate occurring in South-West Africa. The horizontal intensity has diminished at a gradually increasing rate, the maximum change being near Cape Town. The declination appears to have varied at a high rate until about 1928, and much more slowly since then. The greatest total changes are found near Durban. The results are presented in the form suggested by Ljungdahl. Maps with highly smoothed isomagnetic lines are used to show the probable ‘normal’ values of three magnetic elements (declination, inclination, and horizontal intensity), i.e. the component of the field not due to local magnetic disturbance. At each point of actual observation is placed a symbol indicating to what extent the observed value differs from that obtained by interpolation between the isomagnetic lines.

An examination of radio-auroral aspect sensitivity

1985 ◽  
Vol 63 (7) ◽  
pp. 1005-1012 ◽  
Author(s):  
D. R. Moorcroft
Keyword(s):  
Magnetic Field ◽  
Plasma Waves ◽  
Magnetic Field Direction ◽  
Anomalous Resistivity ◽  
Earth’S Magnetic Field ◽  
Earth's Magnetic Field ◽  
E Region ◽  
Radar Wave ◽  
The Magnetic Field ◽  
Aspect Sensitivity

An attempt has been made to account for the experimental observations of scattering at angles away from perpendicularity to the earth's magnetic field (aspect sensitivity). First, it was necessary to develop a scattering model appropriate for the plasma waves generally assumed to be responsible for the scattering, consisting of an assembly of irregularities, each one a wave with a Gaussoidal envelope. Then, effects were included for off-perpendicular propagation of plasma waves, the perturbation of the magnetic field direction owing to the presence of auroral currents, and refraction of the radar wave in the E region. Even when possible effects from anomalous resistivity are included, many of the experimental observations require scattering models consisting of irregularities that are elongated along the direction of the earth's magnetic field by only a few plasma wavelengths (in some cases no more than one or two wavelengths). This is physically unreasonable and suggests that our understanding of auroral E-region irregularities and (or) the scattering processes responsible for auroral echoes is still incomplete.

scholarly journals Animal navigation: a noisy magnetic sense?

2020 ◽  
Vol 223 (18) ◽  
pp. jeb164921
Author(s):  
Sönke Johnsen ◽  
Kenneth J. Lohmann ◽  
Eric. J. Warrant
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
Time Course ◽  
Positional Information ◽  
Time Averaging ◽  
Earth’S Magnetic Field ◽  
Long Time ◽  
Earth's Magnetic Field ◽  
Magnetic Sense ◽  
Natural Settings

ABSTRACTDiverse organisms use Earth's magnetic field as a cue in orientation and navigation. Nevertheless, eliciting magnetic orientation responses reliably, either in laboratory or natural settings, is often difficult. Many species appear to preferentially exploit non-magnetic cues if they are available, suggesting that the magnetic sense often serves as a redundant or ‘backup’ source of information. This raises an interesting paradox: Earth's magnetic field appears to be more pervasive and reliable than almost any other navigational cue. Why then do animals not rely almost exclusively on the geomagnetic field, while ignoring or downplaying other cues? Here, we explore a possible explanation: that the magnetic sense of animals is ‘noisy’, in that the magnetic signal is small relative to thermal and receptor noise. Magnetic receptors are thus unable to instantaneously acquire magnetic information that is highly precise or accurate. We speculate that extensive time-averaging and/or other higher-order neural processing of magnetic information is required, rendering the magnetic sense inefficient relative to alternative cues that can be detected faster and with less effort. This interpretation is consistent with experimental results suggesting a long time course for magnetic compass and map responses in some animals. Despite possible limitations, magnetoreception may be maintained by natural selection because the geomagnetic field is sometimes the only source of directional and/or positional information available.

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