It is unusual to find bare charges in nature. Usually matter is electrically neutral. What would happen if we caused the charges in a linear dipole to oscillate back and forth harmonically? Where would the dipole radiate?
Given the previous work with impulsively driven point charges, we would expect the charges to radiate when they are undergoing the greatest acceleration. For a harmonic oscillator this would be when the charges are furthest apart at their maximum extent. In the following movie, a positive and a negative charge are moving away from each other and a force is applied accelerating the charges back toward the center of the dipole. The acceleration goes to zero as the charges are pulled back and pass through center of the dipole. The static Coulomb fields have been turned off so we can concentrate on the radiation.
On the trip out as the charges begin to accelerate, E1 to E4, radiation developes around the charges much like the radiation for two independent point charges. But as the radiation propagates outward E18 we see a complicated region (red region) develop at the center of the dipole. This is a region of rapidly changing electric and magnetic fields and is birth place for the radiation from the dipole. This region about the dipole is called the induction zone.
As this region propagates outward from the dipole we see it weaken but it is clearly strongest at the center of the dipole, and not at the ends which is characteristic of dipole radiation.
Go to Far Fields.