Define parameters of earth's magnetic field.

Explanation

Possible causes of earth.s magnetism: 1. Since every substance is made up of charged particles (protons and electrons), hence substance rotating about an axis will become magnetised. The earth.s magnetism is also due the rotation of the earth about its own axis.
2. The gases in the atmosphere are in the ionised states. The high energy radiation from the Sun ionises the atoms in the upper part of the atmosphere. The radioactivity of the atmosphere and cosmic rays also ionise the gases in the atmosphere. Hence, due to rotation of the earth, strong electric currents flow. Due to action of these currents, the earth is magnetised
3. Earth has charged molten fluid. The charged fluid rotates along with earth and set unit currents which may be the reason of earth.s magnetism. This effect is known as Dynamo effect
Magnetic Elements of Earth: The physical quantities, which determine the intensity of earth.s total magnetic field completely (both in magnitude and direction), are called magnetic elements. Following are three magnetic elements of earth:
1. Magnetic declination: Declination at a place is the angle between the geographical meridian and the magnetic meridian. It is denoted by `theta`.
If ABCD and AB.C.D represent magnetic and geographical meridian, then `angleBAB.= theta` represents the magnetic declination.
2. Magnetic inclination or dip: Dip at a place is defined as the angle made by the direction of the intensity of the earth.s total magnetic field with the horizontal direction. It is denoted by `delta`.
3. Horizontal component of earth.s magnetic field. It is the component of earth.s magnetic field along the horizontal direction. It is denoted by `B_(h)`