Significance of Earth’s magnetic field
– Earth’s magnetic field deflects solar wind, protecting the ozone layer from harmful ultraviolet radiation.
– Gas caught in magnetic field bubbles is stripped off by solar winds.
– Mars lost its atmosphere due to the dissipation of its magnetic field.
– Paleomagnetism studies the past magnetic field of the Earth.
– Magnetostratigraphy uses magnetic field reversals to date rocks and sediments.
Characteristics of Earth’s magnetic field
– Earth’s magnetic field can be represented by a three-dimensional vector.
– Declination is the angle between magnetic North and true North.
– Inclination is the angle between the magnetic field and the horizontal plane.
– Intensity of the field is proportional to the force it exerts on a magnet.
– Common coordinate systems used to represent the field are North, East, and Down.
Intensity of Earth’s magnetic field
– Earth’s magnetic field intensity is measured in microteslas (μT).
– A strong refrigerator magnet has a field intensity of about 10,000μT.
– Intensity decreases from the poles to the equator.
– South Atlantic Anomaly has the minimum intensity.
– Intensity can change over time in cycles of approximately 200 million years.
Inclination and Declination of Earth’s magnetic field
– Inclination is the angle between the magnetic field and the vertical direction.
– Declination is the angle between the magnetic field and true north.
– In the northern hemisphere, the field points downwards.
– At the North Magnetic Pole, the field is straight down.
– At the magnetic equator, the field is horizontal.
– At the South Magnetic Pole, the field is straight up.
– Declination can be estimated by comparing compass heading with celestial pole direction.
– Maps provide information on declination.
– Isogonic lines represent fixed declination on a chart.
– Declination varies geographically.
Magnetic Poles and their movement
– North and south poles of a magnet were first defined by Earth’s magnetic field.
– North pole of a magnet is attracted by Earth’s North Magnetic Pole.
– Earth’s North Magnetic Pole is actually the south pole of its magnetic field.
– Opposite poles of a magnet attract each other.
– Earth’s magnetic field is directed downward into the Earth at the North Magnetic Pole.
– Magnetic poles can be defined locally or globally.
– Local definition is the point where the magnetic field is vertical.
– Inclination of Earth’s field is 90° downwards at North Magnetic Pole.
– Inclination of Earth’s field is -90° upwards at South Magnetic Pole.
– North and South Magnetic Poles wander independently of each other.
– North Magnetic Pole can move up to 40 kilometers per year.
– Over the last 180 years, North Magnetic Pole has migrated northwestward.
– North Magnetic Pole is currently about 600 kilometers from Resolute Bay.
– Inclination of Earth’s magnetic field is 90° downwards at North Magnetic Pole.
– Inclination of Earth’s magnetic field is -90° upwards at South Magnetic Pole.
– Inclination of Earth’s magnetic field varies at different locations on the globe.
– Inclination is an important parameter to define the position of magnetic poles.
– Inclination is measured to determine the local position of magnetic poles.
– One of the first uses for a magnet was as a compass needle.
– A compass needle aligns with Earth’s magnetic field.
– North pole of a compass needle points towards Earth’s North Magnetic Pole.
– Compass navigation relies on the alignment of magnetic poles.
– Magnetic poles play a crucial role in determining direction using a compass. Source: https://en.wikipedia.org/wiki/Earth%27s_magnetic_field
Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magnetic field is generated by electric currents due to the motion of convection currents of a mixture of molten iron and nickel in Earth's outer core: these convection currents are caused by heat escaping from the core, a natural process called a geodynamo.
The magnitude of Earth's magnetic field at its surface ranges from 25 to 65 μT (0.25 to 0.65 G). As an approximation, it is represented by a field of a magnetic dipole currently tilted at an angle of about 11° with respect to Earth's rotational axis, as if there were an enormous bar magnet placed at that angle through the center of Earth. The North geomagnetic pole actually represents the South pole of Earth's magnetic field, and conversely the South geomagnetic pole corresponds to the north pole of Earth's magnetic field (because opposite magnetic poles attract and the north end of a magnet, like a compass needle, points toward Earth's South magnetic field, Ellesmere Island, Nunavut, Canada.
While the North and South magnetic poles are usually located near the geographic poles, they slowly and continuously move over geological time scales, but sufficiently slowly for ordinary compasses to remain useful for navigation. However, at irregular intervals averaging several hundred thousand years, Earth's field reverses and the North and South Magnetic Poles respectively, abruptly switch places. These reversals of the geomagnetic poles leave a record in rocks that are of value to paleomagnetists in calculating geomagnetic fields in the past. Such information in turn is helpful in studying the motions of continents and ocean floors in above the ionosphere that is defined by the extent of Earth's magnetic field in space. It extends several tens of thousands of kilometres into space, protecting 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 Earth from harmful ultraviolet radiation.
