The Earth’s Magnetic Field and the Magnetosphere
The Earth as a whole acts as a magnet. The field is not only attached to the Earth, but it extends far outside the atmosphere. Its direction at any point in space is the direction found by the vector sum of its horizontal and vertical components. |
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| Objective |
| The Earth as a whole acts as a magnet. The field is not only attached to the Earth, but it extends far outside the atmosphere. Its direction at any point in space is the direction found by the vector sum of its horizontal and vertical components. |
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| Introduction and history |
| The Earth’s magnetic field has been linked to navigation for over 1000 years, long before people had any clues about its origin. The compass – a slender magnet that can rotate freely, was in old days and still is a valuable aid for navigators. |
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| Electric currents and particle movements in the geomagnetic field |
| Charged particles from the Sun or cosmic rays entering the Earth’s magnetic field give rise to many different phenomena. We will briefly review some important particle characteristics. |
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| The geomagnetic elements |
| The Earth behaves magnetically almost as if a bar magnet was located near its center. The locations where its magnetic axis crosses the surface are called the magnetic poles. |
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| Spherical harmonic analyses |
| To determine B at all places on the Earth’s surface, we have to carry out a harmonic analysis of the observed data. In a spherical harmonic analysis, the measured values are equalized. |
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| Magnetic variations |
| The Earth’s magnetic field exhibits a variety of fluctuations. The strength of the field can suddenly decrease by up to more than 2% and than slowly increase again. These magnetic variations can be divided into two main categories. |
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| The Magnetosphere |
| New observations, especially satellite observations, have shown that the simple dipole description does not represent the Earth’s magnetic (BE) field very well, especially at great distances from the Earth. |
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| The Earth’s magnetic field at great distances from the Earth |
| We will now calculate the stand-off distance – i. e. the distance to the magnetopause, to the solar wind in the equatorial plane on the dayside. The solar wind presses on the magnetic field. |
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