what is the effect of earth magnetic field on radio wave?

What kind of information will you get from this blog?

1. What is earth megnetic field?
2. what is the empect of earth's magnetic field?
3. what is the effect of earth magnetic field on radio wave ?

 

The earth's magnetic field exerts a deflecting force on the moving electrons. This force is proportional to the product of instantaneous velocity of the electron and the component of earth's magnetic field at right angles to the velocity of the electron, and the direction of this force is at right angles to both the velocity of the electron and to the component of the magnetic field exerting the force. Since the electrons move along the electric field of the radio wave, a component of earth's magnetic field at right angles to this electric field exerts a force at right angles to both the electric field and this magnetic field Then, electron follows an elliptical path as depicted in figer (a) and (b).The electron develops components of velocity at right angles to the electric field of the wave in following this elliptical path. Out of the total energy absorbed from the electric field of the wave, the electron now re-radiates a part thereof with a polarization rotated 90° in space with respect to the polarization of the incident electromagnetic wave. Generally, this re-radiated field differs in time phase from the field of the incident wave. Now, the resultant wave is a combination of the incident wave and hence, the re-radiated wave is elliptically polarized. Hence, the component of earth's magnetic field at right angles to the electric field of the incident plane polarized wave makes a radio wave to get elliptically polarized after it has travelled some distance in the ionosphere.

In the ionized medium, the average velocity of the electron is inversely proportional to frequency. Therefore, the influence of earth's magnetic field on the paths of the vibrating electrons is greater, the lower the frequency of the incident wave. Hence, at very high frequencies, the elliptical path followed by the electron is very narrow, as depicted in fig. (a). When the frequency is decreased, both the major and minor axes of the ellipse increase as illustrated in fig. (b). With continued reduction in frequency, the size of the ellipse continuously increases until at some frequency in the proximity of 1400 kHz, termed as the "gyro-frequency", cyclotron resonance takes place and the electron follows a spiral path of continuous increasing radius as illustrated in fig.  (c) and continuously increasing velocity. When the frequencies are lower than the gyro-frequency, the electrons follow rather complicated paths with components of velocity both parallel and at right angles with the plane of polarization. It is the component of earth's magnetic field at right angles to the electric field of the wave that affects the polarization of the radio wave. In case the earth's magnetic field is in the same direction as the electric field of the radio wave, the magnetic field fails to have any effect on the radio wave.

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The earth's magnetic field in addition to influencing the polarization of the radio wave also causes the wave to get split up into two components namely, the ordinary ray and the extra-ordinary ray. These two have elliptical polarization and rotate in opposite directions. Therefore, the two rays suffer unequal bending by the ionized medium and, follow slightly different paths, have different velocities and different rates of energy absorption. This splitting of ray into two parts by the magnetic field of the earth is known as the "magneto ionic splitting". of the extra- ordinary ray relative to that of the ordinary ray depends upon the magnitude of the magnetic effects.

conclusion

By this article you gone a learn about how the earth's magnetism affects the flow of raido waves.