The only relativistic theory I know for the field of a moving point charge is by applying a Lorentz boost
Aμα
to the Electromagnetic tensor:
.
We choose c=1.
Aμα =
C
S
0
0
S
C
0
0
0
0
1
0
0
0
0
1
where C = cosh φ and S = sinh φ .
φ is the ‘rapidity’.
The tensor in the boosted frame is F'μν =
AμαAνβ
Fαβ.
For a motionless point change at the origin sufficient to produce a field of magnitude 1 at distance 1 the field is:
See this for calculation of F'01.
N.B. the coordinates x, y and z are still those of the point charge’s frame!
t = Ct' − Sx', x = Cx' − St', y = y', z = z'.
and we have:
F'μν = ((Cx' − St')2 + y'2 + z'2)−3/2
0
−(Cx' − St')
−Cy'
−Cz'
Cx' − St'
0
−Sy'
−Sz'
Cy'
Sy'
0
0
Cz'
Sz'
0
0
The magnetic field is everywhere perpendicular both to the velocity and the displacement vector from the observer to the charge.
The point charge is traveling in the x direction.
Note that the x component of the magnetic field (F32) is 0 everywhere.
At the event (t', x', y', z') = (0, 0, 0, 1) the electric field is
(0, 0, C) and the magnetic field is (0, S, 0).
At the event (0, 1, 0, 0) the electric field is (C−2, 0, 0) and the magnetic field is (0, 0, 0).