We regard the observation points near the circular source, so that the observation time is equal to the source time
and the retardation can be neglected. We see the
component of the electric field in the plane
changing with time. When the time
is running, in the background you see the current position of the charge in the plane
as a red point. The displayed domain of the electric field is 6 meters by 6 meters with 400 vectors. The
range goes from -3 meters to +3 meters. A good observation of the source is at
. The minimum and maximum values of
are 0.1 meter and 2 meters. To observe relativistic effects, set
to their maximum values.
The Heaviside-Feynman formulas are defined in The Feynman Lectures on Physics: Mainly Electromagnetism and Matter
, Chapter 21; and Klassische Elektrodynamik
, 4. Auflage, Chapter 6.5, by J. D. Jackson.