Magnetic dip

Inclination (from the Latin inclinare = (back ) tend to incline ) referred to in geophysics the angle of the local earth's magnetic field to the horizontal.

Earth's magnetic field

The field lines of Earth's magnetic field occur in all places south of the magnetic equator ( not only at the pole ) under a more or less steep angle ( inclination ) of the earth's surface, sometimes run far ausschwingend by the near-Earth space and occur in the northern hemisphere at a similar angle into the earth's surface again. This means that a mounted on a horizontal axis and aligned to magnetic north magnetic needle assumes an inclined position parallel to the field lines. The angle of inclination relative to the horizontal is in the German-speaking area about 62 ° to 70 ° ( from south to north, as of 2010), at the magnetic poles exactly 90 °, the magnetic equator is 0 °.

Due to the temporal variability of the Earth's magnetic field is also subject to the inclination of long-term changes. In German-speaking countries it remains present almost constant. The greatest change is found with -20 minutes of arc per year in eastern Brazil.

To measure the inclination, Earth inductor serves. This contains a rotatably mounted coil is oriented so that its axis is parallel to the earth's magnetic field. If no field lines are cut, no more electric voltage is induced. The angle between the coil axis and the horizontal plane corresponding to the inclination.

Magnetic compasses

As for the determination of the north direction with a magnetic compass is only the horizontal component of the magnetic field lines of importance, and the needle should also remain in a horizontal position to allow a flat design of the compass can, the inclination must be considered in the design of such a compass or individually compensated be. Does not happen that or not enough, shows the compass needle down (on the northern hemisphere ) or upward ( in the southern hemisphere ). If excessive inclination to the magnetic needle can no longer rotate and clamped -free, which may have a false indication of the result.

To avoid this effect, the two pin halves are usually balanced by different weight. Such compasses can be used only in a limited Inklinationsbereich. Some manufacturers provide for their compass models at a range different doses, which are designed for one specific Inklinationszone the earth. We distinguish between up to five such zones.

Another design possibility is the mechanical decoupling of tilting magnetic element and held horizontally direction pointer. Compasses with such " global needles " are used in all Inklinationszonen.

History

The inclination was first observed by Georg Hartmann. He described in a letter of 4 March 1544 Duke Albrecht of Prussia not only about 9 ° East end declination amount but also the effect of the inclination:

The first Inklinationsbussole constructed about 1580 Robert Norman.

Johan Carl Wilcke published 1768 in Stockholm, the first global Inklinationskarte.

Biological Significance

The inclination serve many migratory birds as a " compass " for bird migration. In contrast to the technical compass the magnetic sense over a registration of change of the inclination angle works. On the way to the south ( to the equator ) birds fly so in the direction of " decreasing inclination angle ".