■ MAGNETIC INCLINATION or MAGNETIC DIP
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◇ Magnetic dip, dip angle, or magnetic inclination is the angle made with the horizontal by the Earth's magnetic field lines.
◇ In simple terms, magnetic inclination is the angle made by a compass needle when the compass is held in a vertical orientation.
◇ The magnetic equator is the irregular imaginary line, passing round the earth near the equator, on which a magnetic needle has no dip (because magnetic field lines are parallel to the horizontal at the equator).
◇ Again, the magnetic equator, like the magnetic field and poles, is not fixed.
◇ Magnetic dip at the magnetic equator is 0,֯ and at the magnetic poles, it is 90.
◇ Importance: The phenomenon of magnetic dip is important in aviation, as it causes the aeroplane's compass to give erroneous readings during banked turns and airspeed changes. Necessary corrections need to be made to the compass reading to stay in the right course.
■ GEOMAGNETIC POLES
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◇ The Geomagnetic poles (dipole poles) are the intersections of the Earth's surface and the axis of a bar magnet hypothetically placed at the centre the Earth.
◇ There is such a pole in each hemisphere, and the poles are called as "the geomagnetic north pole" and "the geomagnetic south pole", respectively.
◇ Approximately, geomagnetic dipole is currently tilted at an angle of about 11 degrees to Earth's rotational axis.
◇ On the other hand, the magnetic poles (the magnetic north pole and the magnetic south pole) are the points at which magnetic needles become vertical.
◇ The difference in the position of magnetic poles and geomagnetic poles is due to the uneven and complex distribution of the earth’s magnetic field.
■ MAGNETOSPHERE
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◇ The magnetosphere is the region above the ionosphere that is defined by the extent of the Earth's magnetic field in space.
◇ It extends several tens of thousands of kilometres 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.
◇ Many cosmic rays are kept out of the Solar system by the Sun's magnetosphere called heliosphere.
■ MAGNETOPAUSE
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◇ Earth's magnetic field, predominantly dipolar at its surface, is distorted further out by the solar wind.
◇ The solar wind exerts a pressure. However, it is kept away by the pressure of the Earth's magnetic field.
◇ The magnetopause, the area where the pressures balance, is the boundary of the magnetosphere.
◇ Despite its name, the magnetosphere is asymmetric, with the sunward side being about 10 Earth radii out but the other side stretching out in a magnetotail that extends beyond 200 Earth radii.
