We therefore need a record of how the position and strength of the Earth's magnetic field has changed over time. The record of how the field has changed is referred to as a secular variation curve and is used to calibrate the measured information to obtain a calendar date (Clark et al.
Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from the Earth's interior to where it meets the solar wind, a stream of charged particles emanating from the Sun.
The North and South magnetic poles wander widely, but sufficiently slowly for ordinary compasses to remain useful for navigation. The magnetosphere is the region above the ionosphere and extends several tens of thousands of kilometers into space, protecting the Earth from the charged particles of the solar wind and cosmic rays that would otherwise strip away the upper atmosphere, including the ozone layer that protects the Earth from harmful ultraviolet radiation.
Coronal Mass Ejections (CMEs) reach Earth affecting planetary magnetics, sparking geomagnetic storms, shifting ocean and jet stream currents in the Pacific Ring of Fire, creating unusual and extreme global weather patterns, creating unstoppable Earth changes, and affecting the behavior patterns of all sentient life forms. Earth's last magnetic reversal took place 786,000 years ago and happened very quickly, in less than 100 years -- roughly a human lifetime. Earth's magnetic field, which protects the planet from huge blasts of deadly solar radiation, has been weakening over the past six months, according to data collected by a European Space Agency (ESA) satellite array called Swarm. The solution to a long-standing puzzle, why magnetic north sits off the coast of Canada, rather than at the North Pole, may have been found in the strange, lopsided nature of Earth's inner core. For migratory birds and sea turtles, the ability to sense the Earth's magnetic field is crucial to navigating the long-distance voyages these animals undertake during migration. Humans may have a sixth sense after all, suggests a new study finding that a protein in the human retina, when placed into fruit flies, has the ability to detect magnetic fields. A light-sensitive protein in the human eye has been shown to act as a "compass" in a magnetic field, when it is present in flies' eyes.
In order to date environmental events from Earth's history such as meteorite impacts or climate change - geologists have long studied variations in slow-growing seafloor sedimentary rocks called ferromanganese crusts that build up in layers over the eons.
Scientists have managed to push back the date for the earliest known presence of a magnetic field on Earth by about 250 million years. Building on prior investigation into the biological mechanisms through which monarch butterflies are able to migrate up to 2,000 miles from eastern North America to a particular forest in Mexico each year, neurobiologists at the University of Massachusetts Medical School (UMMS) have linked two related photoreceptor proteins found in butterflies to animal navigation using the Earth's magnetic field. The magnetic equivalent of electricity in a 'spin ice' material: atom sized north and south poles in spin ice drift in opposite directions when a magnetic field is applied. Princeton University scientists have shown that, in ancient times, the Earth's magnetic field was structured like the two-pole model of today, suggesting that the methods geoscientists use to reconstruct the geography of early land masses on the globe are accurate. The flow of seawater across Earth's surface could be responsible for small fluctuations in the planet's magnetic field, a controversial new study says. NASA's Swift satellite reported multiple blasts of radiation from a rare object known as a soft gamma repeater, or SGR. An enormous eruption has found its way to Earth after traveling for many thousands of years across space. Based on studies of old volcanic basalt, scientists know that the EarthOs magnetic field reverses at irregular intervals, ranging from tens of thousands to millions of years. An unexpected, thick layer of solar particles inside Earth's magnetic field suggests there are huge breaches in our planet's solar defenses. Scientists have found two large leaks in Earth's magnetosphere, the region around our planet that shields us from severe solar storms. NASA's five THEMIS spacecraft have discovered a breach in Earth's magnetic field ten times larger than anything previously thought to exist. Ancient lava flows are guiding a better understanding of what generates and controls the Earth's magnetic field - and what may drive it to occasionally reverse direction. Rapid changes in the churning movement of Earth's liquid outer core are weakening the magnetic field in some regions of the planet's surface, a new study says.
Earth's magnetic field is weakening in staggered steps, a new analysis of centuries-old ships logs suggests.The finding could help scientists better understand the way Earth's magnetic poles reverse. One of the most fascinating natural phenomena on Earth is the flipping of its magnetic field, which has occurred hundreds of times in the last 160 million years. After some 400 years of relative stability, Earth's North Magnetic Pole has moved nearly 1,100 kilometers out into the Arctic Ocean during the last century and at its present rate could move from northern Canada to Siberia within the next half-century.
A long look at a young pulsar with NASA's Chandra X-ray Observatory revealed unexpectedly rapid cooling, which suggests that it contains much denser matter than previously expected.
Earth's magnetic field has flipped many times over the last billion years, according to the geologic record. Today it is about 10 percent weaker than it was when German mathematician Carl Friedrich Gauss started keeping tabs on it in 1845, scientists say. Energized particles and electromagnetic waves are filtered through it towards the Earth, colliding with the ionized atoms of hydrogen, oxygen, and helium in the atmosphere, generating interactions and  chemical reactions in the atmosphere. This interaction will have a plasma convection behavior as well, as energized parts will be pushed towards Earth, while less energized particles seek out the field of the Earth, being trapped by the magnetic field.
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License. The solution to a long-standing puzzle, why magnetic north sits off the coast of Canada, rather than at the North Pole, may have been found in the strange, lopsided nature of Earth's inner core.
As the inner core cools, crystallizing iron releases impurities, sending lighter molten material into the liquid outer core. In the last decade, seismic waves from earthquakes revealed the inner core looks like a navel orange, bulging slightly more on its western half. Peter Olson and Renaud Deguen, geophysicists at Johns Hopkins University, set out to test this theory, called translational instability.
Olson and Deguen found that adding inner-core asymmetry shifted magnetic north away from the center of the Earth, into the cooling hemisphere. Geophysicist Bruce Buffett said Olson and Deguen’s research is intriguing, but there are still questions about the underlying theory.
Above: potential energy plots for arrangements of 4 charges - 2 positive charges (red centres) and 2 negative charges (blue centres) of equal magnitude. On the bottom-left are two positive charges in RGB, illustrating a common equipotential, in green, enclosing both charges.On the bottom-right a positive charge (red centre) is shown opposite a negative charge (blue centre) of equal magnitude. The charged particles in this plot will tend to move so as to occupy regions of low potential - the  two particles of like charge (above left) are essentially sitting on a 'hill' and will tend to 'roll-away' or move apart from one-another. The plots shown on this page do not plot the force, nor the field strength, since these are vector fields and we would have to indicate direction as well as magnitude, so, for simplicity, we have plotted the electric potential, phi, given by equation 5. Electric Force on Moving ChargesIf we have a beam of moving charges, such as a beam of electrons (each of which has a mass M and negative charge of magnitude q) moving between two charged metal plates, then the beam will be deflected toward the plate of opposite charge (opposite charges attract!). The Magnetic ForceMagnetism has some similarities to the electric force and the two are intimately connected. Motion of Charged Particles in Magnetic FieldsTo calculate the trajectory of a charged particle moving in a magnetic field, we need a coordinate system for our vectors! An example of a magnetic field is illustrated below: electric charge (taken as positive by convention, though in reality it is the negative electrons which move in the opposite direction) flowing in an electrical wire as shown by the blue arrow generates a magnetic field which loops around the wire in the direction shown (red circular arrows). The radius of gyration, the radius of the helix, is given by r; P is the period (time taken) for the electron to complete one revolution of the helix and dx is the distance moved along the x-axis during one complete turn. When the field-lines converge towards the poles, this indicates a strengthening of the magnetic field in this region. Specific events can cause the magnetic materials to record information about the direction and strength of the magnetic field.
However, at irregular intervals averaging several hundred thousand years, the Earth's field reverses and the North and South Magnetic Poles relatively abruptly switch places.
The rapid flip, much faster than the thousands of years most geologists thought, comes as new measurements show the planet's magnetic field is weakening 10 times faster than normal and could drop to zero in a few thousand years.
The layers can be dated by various means, such as by analyzing radioactive isotopes, but those methods don't provide accurate dating on small scales: a millimeter of rock, for example, can include information that spans as much as hundreds of thousands of years.
The shift widens the distance between true north and magnetic north, which is the direction a compass needle points.
Experts know birds possess an internal magnetic compass, but there is disagreement about what form it takes. The findings may lead to a better understanding of historical continental movement, which relates to changes in climate. If so, the research would challenge the widely accepted theory that Earth's magnetic field is generated by a churning molten core, or dynamo, in the planet's interior.


Now, astronomers report an in-depth study of these eruptions using the European Space Agency's XMM-Newton and International Gamma-Ray Astrophysics Laboratory (INTEGRAL) satellites. Volcanic basalt rock contains magnetite, and when the rock cools, its magnetic properties are frozen, recording the Earth's magnetic field of the time.
These breaches indicate that during the next period of high solar activity, due to start in 2012, Earth will experience some of the worst solar storms seen in decades. The leaks are defying many of scientists' previous ideas on how the interaction between Earth's magnetosphere and solar wind occurs: The leaks are in an unexpected location, let in solar particles in faster than expected and the whole interaction works in a manner that is completely the opposite of what scientists had thought. Solar wind can flow in through the opening to "load up" the magnetosphere for powerful geomagnetic storms.
The main magnetic field, generated by turbulent currents within the deep mass of molten iron of the Earth's outer core, periodically flips its direction, such that a compass needle would point south rather than north. The planet's magnetic field flips - north becomes south and vice versa - on average every 300,000 years. If that happens, Alaska may be in danger of losing one of its most stunning natural phenomena ? the Northern Lights. The pulsar's cool temperature and the vast magnetic web of high-energy particles that surrounds it have implications for the theory of nuclear matter and the origin of magnetic fields in cosmic objects. But only in the past decade have scientists developed and evolved a computer model to demonstrate how these reversals occur. Like a Kryptonite-challenged Superman, its strength has steadily and mysteriously waned, leaving parts of the planet vulnerable to increased radiation from space.
James Ross located the pole for the first time in 1831 after an exhausting arctic journey during which his ship got stuck in the ice for four years In 1904, Roald Amundsen found the pole again and discovered that it had moved at least 50 km since the days of Ross.
It has been established that the outer space has an average temperature of 2.7 ° K (helium particles at these temperatures are superconductors) while the corona of stars can reach 1 million ° K. It is surrounded by a liquid outer core (mostly iron and nickel), a rocky, viscous mantle layer and a thin, solid crust. This upwelling, combined with the Earth's rotation, drives convection, forcing the molten metal into whirling vortices. Geoscientists recently explainedthe asymmetry by proposing a convective loop: The inner core might be crystallizing on one half and melting on the other.
They ran numerical models simulating the forces that generate Earth’s magnetic field, and included a lopsided inner core. Olson and Deguen's research was detailed online July 1 in the journal Nature Geoscience.
Magnetic particles trapped and aligned in rocks reveal that the magnetic north pole wandered around the Western Hemisphere over the past 10,000 years, and circled the Eastern Hemisphere before that — a result mirrored by the numerical test. On this scale green represents zero potential, such as the points at which the negative and positive charge potentials cancel. On this RGB scale green illustrates values close to zero, where the positive and negative potentials cancel one-another.Remember electric charge comes in two 'flavours' - negative (-) and positive and like charges (- and - or + and +) repel whereas opposite charges (- and + or + and -) attract! The particles of opposite charges, above right, will tend to be attracted to the region of low potential between them - unlike charges attract!Electric charges are surrounded by electric fields which exert forces on other nearby electric charges. Like the electric force, magnetism appears to have two 'flavours' - opposite poles of two bar magnets (north and south magnetic poles) will attract each other,  whilst like poles repel. The trajectory is plotted below using parametric equations (parameter t) with the radius of the helix in the y(t) direction. According to classical physics, an accelerating charged particle (remember that in physics acceleration can be a change in speed or a change in direction) emits electromagnetic radiation ('light') as photons (particles of light). The Earth acts like a giant bar magnet - it has a magnetic north pole (near to its geometric South Pole) and a magnetic south pole (near to its geometric North Pole). This causes the gyrating particles to gyrate in smaller orbits (radius of orbit, r is inversely proportional to B) and in such a non-uniform magnetic field the speed of the particles along the field-lines does change - it slows down (the right-hand rule indicates a force acting against the path of the helix). If we know how the magnetic field has changed over time, and we can measure the information held within the magnetic minerals about the past magnetic field, we can produce a date. Roughly speaking it is the field of a magnetic dipole currently tilted at an angle of about 10 degrees with respect to Earth's rotational axis, as if there were a bar magnet placed at that angle at the center of the Earth.
These reversals of the geomagnetic poles leave a record in rocks that are of value to paleomagnetists in calculating geomagnetic fields in the past. One idea is that tiny magnets in the beak wired to the nervous system detect lines of magnetic force.
By taking a closer look at the 1.1 billion-year-old volcanic rocks on the north shore of Lake Superior, the researchers have found that Earth's ancient magnetic field was a geocentric axial dipole -- essentially a large bar magnet centered in the core and aligned with the Earth's spin axis.
With this data, scientists estimate that the last magnetic field reversal occurred about 780,000 years ago.
Such polarity reversals have occurred hundreds of times at irregular intervals throughout the planet's history - most recently about 780,000 years ago - but scientists are still trying to understand how and why. Scientists already suspected birds' eyes contain molecules that are thought to sense Earth's magnetic field.
The last time this happened was some 780,000 years ago, so we could be heading for another reversal soon. The pole kept going during the 20th century, north at an average speed of 10 km per year, lately accelerating to 40 km per year. These vortices stretch and twist magnetic field lines, creating Earth’s magnetic field. The model does a good job at explaining some but not all of the features of the inner core," said Buffett, a professor at the University of California, Berkeley, who was not involved with the research.
Gathering a longer, more detailed record of the magnetic field's behavior, Olson said, could reveal whether the inner core acts as researchers predict. Becky was a science reporter at The Pasadena Star-News and has freelanced for New Scientist and the American Institute of Physics.
The RGB scale shows the highest charge region in red, the lowest in blue and the algorithm used highlights the contours (equipotentials).On the top-right, two positive charges are shown in an orange-blue scale. The electric force, F, is the product of the electric charge, q, and the electric field strength, E (equation 1 below). Moving electric charge generates a magnetic field and a magnetic field will accelerate moving electric charges.
Distance dx depends on the x-component of velocity (this is the velocity component parallel to B and this does not change) and if this is zero, then the particle traces a stationary circle.
Magnetic field lines connect these two poles in large hoops which collectively form a doughnut-shaped (toroidal or torus-shaped) magnetic field around the Earth, which diminishes in strength as we travel away from the Earth's surface into space.
However, magnetic fields cannot alter the total speed of particles, as they cannot change the particles' kinetic energy, thus as the particles move slower and slower in the direction of the field line, they move faster and faster in their circular orbits. Unlike a bar magnet, however, Earth's magnetic field changes over time because it is generated by a geodynamo (in Earth's case, the motion of molten iron alloys in its outer core). Such information in turn is helpful in studying the motions of continents and ocean floors in the process of plate tectonics. New findings show that a missing piece of the traditional theory explaining why metals become less conductive when they are heated was needed to complete the puzzle of this field-generating process. The planet's magnetic field is on the move, a normal enough phenomenon, but one that has some rather bizarre implications, such as the need to renumber airport runways. Another is that magnetic fields are ''seen'' via the eyes using a light-sensitive mechanism. Researchers are even more amazed at the strange and unexpected way it forms, overturning long-held ideas of space physics. In a new study, German researchers found that these molecules are linked to an area of the brain known to process visual information.
There, the heat of the Earth's solid inner core churns a liquid outer core composed of iron and nickel.
What is uncertain is whether the weakened field is on the way to a complete collapse and a reversal that would flip the North and South Poles. Currently, the center of the field, called an axis, emerges in the Arctic Ocean west of Ellesmere Island, about 300 miles (500 kilometers) from the geographic North Pole.
The electric field strength is then force per unit of charge (equation 2) meaning the force experienced on a unit test-charge placed in the electric field due to a second, central charge. One key difference is that the magnetic force is the vector cross-product between velocity of the charged particle and the magnetic field strength, B, multiplied by the electric charge (equation 6) - compare this with equation 1 for the electric force.


This emission of radiation causes the gyrating particle to lose energy - it slows down and so the radius of the orbit decreases (the frequency remains unchanged) and in reality the radius of the spiral diminishes as the particle moves - the helix spirals down.
Eventually, the particles execute tiny stationary orbits at high speed and stop moving along the field-line and then their path reverses. This upwelling, combined with the Earth's rotation, drives convection, forcing the molten metal into whirling vortices.
Tampa International Airport on Florida's west coast just finished renaming its three runways, a laborious project that interrupted airport traffic for a month while runways were shut down for repainting. The new research suggests that, for robins at least, the second theory is probably correct.
In that sense, "birds may see the magnetic field," said study lead author Dominik Heyers, a biologist at the University of Oldenburg. Since 1840, when accurate measures of the intensity were first made, the field strength has declined by about 5 percent per century.
The churning acts like convection, which generates electric currents and, as a result, a magnetic field. If we are dealing with stationary charges (electrostatics) then the electric force between two such point charges is also called the Coulomb force.
This vector cross-product means that the force acts in a direction which is at right-angles (perpendicular) to the direction of movement of the particle (given by the velocity vector) and the magnetic field. The blue line represents the Earth's axis of spin, on which lie its geometric poles, and the magnetic field is tilted about 12 degrees relative to this spin-axis (though the field drifts and its angle of tilt changes noticeably every year).Magnetic field lines point from magnetic north to magnetic south - they have to be assigned direction, since the trajectory followed by electrically charged particles (the helices as illustrated above) depends on this direction. In the Van Allen belts, the particles oscillate back-and-forth between the poles once every 0.1-3 seconds!In addition to bouncing back-and-forth between the polar regions, the particles also drift in longitude (the field strength diminishes with distance from the Earth and eventually the field-lines become too weak to confine the particles which can then move from one field-line to another.
German scientists studied 36 European robins and found birds with damage to ''cluster N'' were unable to orientate themselves using the Earth's magnetic field. Human-made compasses work by using Earth as an enormous magnet and orienting a tiny magnet attached to a needle to the planet's north and south poles. If this decline is continuous, the magnetic field could drop to zero and reverse sometime within the next 2,000 years.
The strength of the force decreases by an inverse-square law, meaning that as distance from the source charge is doubled, the force drops to a quarter of its strength. If both electric and magnetic forces act upon a particle, then the total force is given by the Lorentz force law (equation 7). The radiation emitted is also known as cyclotron radiation.Note also, that if the sign of the electric charge on the particle is changed, then the sense of the helix is changed.
Electric field lines similarly have direction - radiating out from a positive charge and inwards to a negative charge (so a positive test charge will follow the field lines). High-energy protons drift westward around the Earth every 0.1 s and lower-energy electrons drift eastward, circling the Earth once every 1 to 10 hours. But the field might not always be in steady decline, according to a new study appearing in tomorrow's issue of the journal Science. Looking along the helix from the origin the direction of B (positive x-axis in this case) a negatively charged particle is seen to spiral clockwise whilst a positively charged particle spirals anti-clockwise. One key difference, however, is that although it is easy to have a single electric charge, positive or negative, it is very hard, if not impossible, to have a single isolated magnetic pole (a monopole) and with a few possible extreme exceptions, a magnetic north is always accompanied by a magnetic south (a dipole).The presence of the Earth's magnetic field is thought to be due to electric charges flowing in the Earth's outer core, which appears to be a metallic liquid.
These velocities are quite fantastic!The AuroraeThe inner radiation belt interacts with the Earth's upper atmosphere - lower energy electrons drop-out and collide with air molecules, exciting and ionising the molecules. The rotational effect helps scientists understand what's happening inside the Earth's core. Epsilon-zero, the curly 'e' with the zero subscript, is the permittivity of free space ( = 8.854 x 10^-12 C^2N^-1m^-2) or the ease with which the electric field traverses a vacuum and its value depends on the choice of units. In this way, the sign of the electric charge on the particle can be determined by analysing its path in a particle detector (such as a bubble chamber).Cyclotron radiation is seen in the magnetospheres of some planets where charged particles get trapped as they spiral along the planet's magnetic field, and also in stars, like the Sun and some neutron stars in X-ray pulsars. Rotation of the Earth sets up currents of moving charges inside this outer core and these charges generate a magnetic field. As the molecules de-excite they emit the excess-energy they gained in the collision as photons of light - the frequency and colour of the photons depends upon the element excited (mostly nitrogen or oxygen) and the flickering curtains of light produced in the upper atmosphere are known as the aurora borealis, or northern lights in northern latitudes, and the aurora australis, or southern lights, in southern latitudes. The r-hat is a unit vector - force has magnitude and direction and this unit-vector indicates the direction of the force, which depends on the sign of the charge.
If the field is sufficiently strong, then the charges will be confined by it, as they gyrate along the magnetic field lines, and the field is reinforced and achieves a fairly stable pattern - this is the electromagnetic dynamo theory.There is an additional complication to the shape of the Earth's magnetic field further from the surface - it gets distorted by the Solar wind and in the lee-side it is drawn out into a comet-shaped tail as it ploughs against the wind.
The total force due to a collection of charges is equal to the spatial summation of the contributions to the force of each individual charge (equation 4). This kind of radiation is often beamed in the direction of particle motion and has non-thermal characteristics. The Solar wind influences the aurorae - if the Solar wind increases in strength then it may supply more electrons to the Van Allen belts and it may also disturb the magnetic field, causing electrons to be dumped from the inner belt into the atmosphere - both effects will increase the aurorae.The Nature of Magnetism - it's all relative!Magnetism and electric phenomena are intimately connected, and yet it seems easier intuitively to understand electric charges and their electrical interactions than to conceptualise magnetism. Synchrotron radiation is emitted by many quasar nuclei - the nuclei of active galaxies that are thought to contain supermassive black holes (at the very least they do contain very strange objects!). Some of these particles leak through the magnetopause and become trapped in the Earth's magnetic field - gyrating along the magnetic field lines. These particles will gyrate around the arc of a field-line, travelling away from one pole and toward the other.
Charged particles trapped in the intense magnetic fields associated with black holes become accelerated to speeds approaching that of light! This is fine where the magnetic field-lines are more or less parallel to one-another, as above the equator (a so-called uniform magnetic field) but towards the poles, the field-lines converge and get squeezed together.
Particles gyrating along the field-lines into these regions experience another phenomenon - they are reflected to travel back along the field-lines in the opposite direction from which they came. Thus they bounce around between northern and southern latitudes, traveling as far poleward as they can before they are reflected, gyrating as they go.
Bring the two wires near to each other - how will the magnetic fields interact?If the wires are parallel (side-by-side) and their currents flow in the same direction, then the wires will become attracted to one-another.
Reverse the direction of flow of current in one of the two wires, so that the two currents flow in opposite directions, and the wires will repel one-another - like currents attract, unlike currents repel. Imagine the electrons flowing from left to right along the wire and now imagine an electron outside the wire and flowing in the same direction and with the same speed as the electrons in the wire.
This is like two wires with like currents - the electron will be attracted toward the wire. As opposite charges attract, and the electron is negatively charged, it as if the wire had somehow gained a net positive charge! Wires are made of metal, and metal atoms are electrically neutral - metals consist of a sea of delocalised electrons bathing a lattice of positive ions, but overall the net charge is zero. The wire still has a zero net electric charge!If the external electron is 'seeing' more positive charge in the wire, then it as if the number of positive ions (atom cores) per unit length of wire had somehow increased! This could happen if the wire shrank and became shorter without effecting the flowing electrons - this would increase the density of positive ions in the wire, without increasing the total number - more positive charges cannot appear since electric charge is conserved - the net charge on the wire must remain zero and does so! That's because length is relative!From the point of view of the electrons moving along, it is the wire that appears to be moving past them in the opposite direction. According to the Theory of Special Relativity moving objects become shorter in the direction of their motion.
However, motion is relative - to the electrons the wire is moving and so the wire shrinks, but to the wire the electrons are moving and so they shrink and become closer together. Thus the electron 'sees' the wire shrink and increase its positive charge density and so the electron is attracted toward the wire by the electric force of attraction. The wire 'sees' the distance between the electrons shorten, increasing electron charge density and the positive wire is attracted to this apparent increase in negative charge by the electric force. The end result is that the wire and electron are attracted to one-another (but since the wire is much heavier it moves less and an experimenter in the lab will see the electron move toward the wire).The conclusion is surprising - electricity and magnetism are manifestations of the same fundamental force, the electromagnetic force, as seen from different points of view!



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Comments

  1. PROBLEM
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  2. MARINA
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